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![Christoph Lameter](/assets/img/avatar_default.png)
page migration currently simply retries a couple of times if try_to_unmap() fails without inspecting the return code. However, SWAP_FAIL indicates that the page is in a vma that has the VM_LOCKED flag set (if ignore_refs ==1). We can check for that return code and avoid retrying the migration. migrate_page_remove_references() now needs to return a reason why the failure occured. So switch migrate_page_remove_references to use -Exx style error messages. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1958 lines
50 KiB
C
1958 lines
50 KiB
C
/*
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* linux/mm/vmscan.c
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*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Swap reorganised 29.12.95, Stephen Tweedie.
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* kswapd added: 7.1.96 sct
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* Removed kswapd_ctl limits, and swap out as many pages as needed
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* to bring the system back to freepages.high: 2.4.97, Rik van Riel.
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* Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
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* Multiqueue VM started 5.8.00, Rik van Riel.
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*/
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/kernel_stat.h>
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#include <linux/swap.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <linux/highmem.h>
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#include <linux/file.h>
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#include <linux/writeback.h>
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#include <linux/blkdev.h>
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#include <linux/buffer_head.h> /* for try_to_release_page(),
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buffer_heads_over_limit */
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#include <linux/mm_inline.h>
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#include <linux/pagevec.h>
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#include <linux/backing-dev.h>
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#include <linux/rmap.h>
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#include <linux/topology.h>
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#include <linux/cpu.h>
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#include <linux/cpuset.h>
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#include <linux/notifier.h>
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#include <linux/rwsem.h>
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#include <asm/tlbflush.h>
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#include <asm/div64.h>
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#include <linux/swapops.h>
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/* possible outcome of pageout() */
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typedef enum {
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/* failed to write page out, page is locked */
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PAGE_KEEP,
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/* move page to the active list, page is locked */
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PAGE_ACTIVATE,
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/* page has been sent to the disk successfully, page is unlocked */
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PAGE_SUCCESS,
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/* page is clean and locked */
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PAGE_CLEAN,
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} pageout_t;
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struct scan_control {
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/* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
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unsigned long nr_to_scan;
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/* Incremented by the number of inactive pages that were scanned */
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unsigned long nr_scanned;
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/* Incremented by the number of pages reclaimed */
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unsigned long nr_reclaimed;
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unsigned long nr_mapped; /* From page_state */
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/* Ask shrink_caches, or shrink_zone to scan at this priority */
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unsigned int priority;
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/* This context's GFP mask */
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gfp_t gfp_mask;
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int may_writepage;
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/* Can pages be swapped as part of reclaim? */
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int may_swap;
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/* This context's SWAP_CLUSTER_MAX. If freeing memory for
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* suspend, we effectively ignore SWAP_CLUSTER_MAX.
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* In this context, it doesn't matter that we scan the
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* whole list at once. */
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int swap_cluster_max;
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};
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/*
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* The list of shrinker callbacks used by to apply pressure to
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* ageable caches.
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*/
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struct shrinker {
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shrinker_t shrinker;
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struct list_head list;
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int seeks; /* seeks to recreate an obj */
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long nr; /* objs pending delete */
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};
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#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
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#ifdef ARCH_HAS_PREFETCH
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#define prefetch_prev_lru_page(_page, _base, _field) \
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do { \
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if ((_page)->lru.prev != _base) { \
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struct page *prev; \
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\
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prev = lru_to_page(&(_page->lru)); \
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prefetch(&prev->_field); \
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} \
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} while (0)
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#else
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#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
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#endif
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#ifdef ARCH_HAS_PREFETCHW
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#define prefetchw_prev_lru_page(_page, _base, _field) \
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do { \
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if ((_page)->lru.prev != _base) { \
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struct page *prev; \
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\
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prev = lru_to_page(&(_page->lru)); \
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prefetchw(&prev->_field); \
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} \
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} while (0)
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#else
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#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
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#endif
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/*
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* From 0 .. 100. Higher means more swappy.
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*/
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int vm_swappiness = 60;
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static long total_memory;
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static LIST_HEAD(shrinker_list);
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static DECLARE_RWSEM(shrinker_rwsem);
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/*
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* Add a shrinker callback to be called from the vm
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*/
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struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
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{
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struct shrinker *shrinker;
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shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
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if (shrinker) {
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shrinker->shrinker = theshrinker;
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shrinker->seeks = seeks;
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shrinker->nr = 0;
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down_write(&shrinker_rwsem);
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list_add_tail(&shrinker->list, &shrinker_list);
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up_write(&shrinker_rwsem);
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}
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return shrinker;
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}
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EXPORT_SYMBOL(set_shrinker);
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/*
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* Remove one
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*/
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void remove_shrinker(struct shrinker *shrinker)
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{
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down_write(&shrinker_rwsem);
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list_del(&shrinker->list);
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up_write(&shrinker_rwsem);
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kfree(shrinker);
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}
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EXPORT_SYMBOL(remove_shrinker);
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#define SHRINK_BATCH 128
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/*
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* Call the shrink functions to age shrinkable caches
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*
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* Here we assume it costs one seek to replace a lru page and that it also
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* takes a seek to recreate a cache object. With this in mind we age equal
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* percentages of the lru and ageable caches. This should balance the seeks
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* generated by these structures.
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*
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* If the vm encounted mapped pages on the LRU it increase the pressure on
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* slab to avoid swapping.
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*
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* We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
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*
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* `lru_pages' represents the number of on-LRU pages in all the zones which
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* are eligible for the caller's allocation attempt. It is used for balancing
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* slab reclaim versus page reclaim.
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*
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* Returns the number of slab objects which we shrunk.
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*/
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int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages)
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{
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struct shrinker *shrinker;
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int ret = 0;
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if (scanned == 0)
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scanned = SWAP_CLUSTER_MAX;
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if (!down_read_trylock(&shrinker_rwsem))
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return 1; /* Assume we'll be able to shrink next time */
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list_for_each_entry(shrinker, &shrinker_list, list) {
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unsigned long long delta;
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unsigned long total_scan;
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unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
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delta = (4 * scanned) / shrinker->seeks;
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delta *= max_pass;
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do_div(delta, lru_pages + 1);
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shrinker->nr += delta;
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if (shrinker->nr < 0) {
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printk(KERN_ERR "%s: nr=%ld\n",
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__FUNCTION__, shrinker->nr);
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shrinker->nr = max_pass;
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}
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/*
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* Avoid risking looping forever due to too large nr value:
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* never try to free more than twice the estimate number of
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* freeable entries.
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*/
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if (shrinker->nr > max_pass * 2)
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shrinker->nr = max_pass * 2;
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total_scan = shrinker->nr;
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shrinker->nr = 0;
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while (total_scan >= SHRINK_BATCH) {
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long this_scan = SHRINK_BATCH;
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int shrink_ret;
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int nr_before;
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nr_before = (*shrinker->shrinker)(0, gfp_mask);
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shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
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if (shrink_ret == -1)
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break;
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if (shrink_ret < nr_before)
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ret += nr_before - shrink_ret;
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mod_page_state(slabs_scanned, this_scan);
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total_scan -= this_scan;
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cond_resched();
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}
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shrinker->nr += total_scan;
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}
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up_read(&shrinker_rwsem);
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return ret;
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}
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/* Called without lock on whether page is mapped, so answer is unstable */
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static inline int page_mapping_inuse(struct page *page)
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{
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struct address_space *mapping;
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/* Page is in somebody's page tables. */
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if (page_mapped(page))
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return 1;
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/* Be more reluctant to reclaim swapcache than pagecache */
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if (PageSwapCache(page))
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return 1;
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mapping = page_mapping(page);
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if (!mapping)
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return 0;
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/* File is mmap'd by somebody? */
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return mapping_mapped(mapping);
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}
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static inline int is_page_cache_freeable(struct page *page)
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{
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return page_count(page) - !!PagePrivate(page) == 2;
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}
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static int may_write_to_queue(struct backing_dev_info *bdi)
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{
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if (current->flags & PF_SWAPWRITE)
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return 1;
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if (!bdi_write_congested(bdi))
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return 1;
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if (bdi == current->backing_dev_info)
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return 1;
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return 0;
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}
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/*
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* We detected a synchronous write error writing a page out. Probably
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* -ENOSPC. We need to propagate that into the address_space for a subsequent
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* fsync(), msync() or close().
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*
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* The tricky part is that after writepage we cannot touch the mapping: nothing
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* prevents it from being freed up. But we have a ref on the page and once
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* that page is locked, the mapping is pinned.
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*
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* We're allowed to run sleeping lock_page() here because we know the caller has
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* __GFP_FS.
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*/
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static void handle_write_error(struct address_space *mapping,
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struct page *page, int error)
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{
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lock_page(page);
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if (page_mapping(page) == mapping) {
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if (error == -ENOSPC)
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set_bit(AS_ENOSPC, &mapping->flags);
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else
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set_bit(AS_EIO, &mapping->flags);
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}
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unlock_page(page);
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}
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/*
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* pageout is called by shrink_list() for each dirty page. Calls ->writepage().
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*/
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static pageout_t pageout(struct page *page, struct address_space *mapping)
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{
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/*
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* If the page is dirty, only perform writeback if that write
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* will be non-blocking. To prevent this allocation from being
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* stalled by pagecache activity. But note that there may be
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* stalls if we need to run get_block(). We could test
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* PagePrivate for that.
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*
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* If this process is currently in generic_file_write() against
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* this page's queue, we can perform writeback even if that
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* will block.
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*
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* If the page is swapcache, write it back even if that would
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* block, for some throttling. This happens by accident, because
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* swap_backing_dev_info is bust: it doesn't reflect the
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* congestion state of the swapdevs. Easy to fix, if needed.
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* See swapfile.c:page_queue_congested().
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*/
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if (!is_page_cache_freeable(page))
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return PAGE_KEEP;
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if (!mapping) {
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/*
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* Some data journaling orphaned pages can have
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* page->mapping == NULL while being dirty with clean buffers.
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*/
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if (PagePrivate(page)) {
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if (try_to_free_buffers(page)) {
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ClearPageDirty(page);
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printk("%s: orphaned page\n", __FUNCTION__);
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return PAGE_CLEAN;
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}
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}
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return PAGE_KEEP;
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}
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if (mapping->a_ops->writepage == NULL)
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return PAGE_ACTIVATE;
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if (!may_write_to_queue(mapping->backing_dev_info))
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return PAGE_KEEP;
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if (clear_page_dirty_for_io(page)) {
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int res;
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_NONE,
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.nr_to_write = SWAP_CLUSTER_MAX,
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.nonblocking = 1,
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.for_reclaim = 1,
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};
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SetPageReclaim(page);
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res = mapping->a_ops->writepage(page, &wbc);
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if (res < 0)
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handle_write_error(mapping, page, res);
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if (res == AOP_WRITEPAGE_ACTIVATE) {
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ClearPageReclaim(page);
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return PAGE_ACTIVATE;
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}
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if (!PageWriteback(page)) {
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/* synchronous write or broken a_ops? */
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ClearPageReclaim(page);
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}
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return PAGE_SUCCESS;
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}
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return PAGE_CLEAN;
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}
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static int remove_mapping(struct address_space *mapping, struct page *page)
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{
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if (!mapping)
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return 0; /* truncate got there first */
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write_lock_irq(&mapping->tree_lock);
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/*
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* The non-racy check for busy page. It is critical to check
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* PageDirty _after_ making sure that the page is freeable and
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* not in use by anybody. (pagecache + us == 2)
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*/
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if (unlikely(page_count(page) != 2))
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goto cannot_free;
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smp_rmb();
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if (unlikely(PageDirty(page)))
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goto cannot_free;
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if (PageSwapCache(page)) {
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swp_entry_t swap = { .val = page_private(page) };
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__delete_from_swap_cache(page);
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write_unlock_irq(&mapping->tree_lock);
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swap_free(swap);
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__put_page(page); /* The pagecache ref */
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return 1;
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}
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__remove_from_page_cache(page);
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write_unlock_irq(&mapping->tree_lock);
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__put_page(page);
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return 1;
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cannot_free:
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write_unlock_irq(&mapping->tree_lock);
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return 0;
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}
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/*
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* shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
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*/
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static int shrink_list(struct list_head *page_list, struct scan_control *sc)
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{
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LIST_HEAD(ret_pages);
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struct pagevec freed_pvec;
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int pgactivate = 0;
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int reclaimed = 0;
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cond_resched();
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pagevec_init(&freed_pvec, 1);
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while (!list_empty(page_list)) {
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struct address_space *mapping;
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struct page *page;
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int may_enter_fs;
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int referenced;
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cond_resched();
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page = lru_to_page(page_list);
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list_del(&page->lru);
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if (TestSetPageLocked(page))
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goto keep;
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BUG_ON(PageActive(page));
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sc->nr_scanned++;
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if (!sc->may_swap && page_mapped(page))
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goto keep_locked;
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/* Double the slab pressure for mapped and swapcache pages */
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if (page_mapped(page) || PageSwapCache(page))
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sc->nr_scanned++;
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if (PageWriteback(page))
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goto keep_locked;
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referenced = page_referenced(page, 1);
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/* In active use or really unfreeable? Activate it. */
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if (referenced && page_mapping_inuse(page))
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goto activate_locked;
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#ifdef CONFIG_SWAP
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/*
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* Anonymous process memory has backing store?
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* Try to allocate it some swap space here.
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*/
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if (PageAnon(page) && !PageSwapCache(page)) {
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if (!sc->may_swap)
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goto keep_locked;
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if (!add_to_swap(page, GFP_ATOMIC))
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goto activate_locked;
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}
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#endif /* CONFIG_SWAP */
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mapping = page_mapping(page);
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may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
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(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
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/*
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* The page is mapped into the page tables of one or more
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* processes. Try to unmap it here.
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*/
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if (page_mapped(page) && mapping) {
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/*
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* No unmapping if we do not swap
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*/
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if (!sc->may_swap)
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goto keep_locked;
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switch (try_to_unmap(page, 0)) {
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case SWAP_FAIL:
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goto activate_locked;
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case SWAP_AGAIN:
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goto keep_locked;
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case SWAP_SUCCESS:
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; /* try to free the page below */
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}
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}
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if (PageDirty(page)) {
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if (referenced)
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goto keep_locked;
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if (!may_enter_fs)
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goto keep_locked;
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if (!sc->may_writepage)
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goto keep_locked;
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/* Page is dirty, try to write it out here */
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switch(pageout(page, mapping)) {
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case PAGE_KEEP:
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goto keep_locked;
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case PAGE_ACTIVATE:
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goto activate_locked;
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case PAGE_SUCCESS:
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if (PageWriteback(page) || PageDirty(page))
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goto keep;
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/*
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* A synchronous write - probably a ramdisk. Go
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* ahead and try to reclaim the page.
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*/
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if (TestSetPageLocked(page))
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goto keep;
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if (PageDirty(page) || PageWriteback(page))
|
|
goto keep_locked;
|
|
mapping = page_mapping(page);
|
|
case PAGE_CLEAN:
|
|
; /* try to free the page below */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the page has buffers, try to free the buffer mappings
|
|
* associated with this page. If we succeed we try to free
|
|
* the page as well.
|
|
*
|
|
* We do this even if the page is PageDirty().
|
|
* try_to_release_page() does not perform I/O, but it is
|
|
* possible for a page to have PageDirty set, but it is actually
|
|
* clean (all its buffers are clean). This happens if the
|
|
* buffers were written out directly, with submit_bh(). ext3
|
|
* will do this, as well as the blockdev mapping.
|
|
* try_to_release_page() will discover that cleanness and will
|
|
* drop the buffers and mark the page clean - it can be freed.
|
|
*
|
|
* Rarely, pages can have buffers and no ->mapping. These are
|
|
* the pages which were not successfully invalidated in
|
|
* truncate_complete_page(). We try to drop those buffers here
|
|
* and if that worked, and the page is no longer mapped into
|
|
* process address space (page_count == 1) it can be freed.
|
|
* Otherwise, leave the page on the LRU so it is swappable.
|
|
*/
|
|
if (PagePrivate(page)) {
|
|
if (!try_to_release_page(page, sc->gfp_mask))
|
|
goto activate_locked;
|
|
if (!mapping && page_count(page) == 1)
|
|
goto free_it;
|
|
}
|
|
|
|
if (!remove_mapping(mapping, page))
|
|
goto keep_locked;
|
|
|
|
free_it:
|
|
unlock_page(page);
|
|
reclaimed++;
|
|
if (!pagevec_add(&freed_pvec, page))
|
|
__pagevec_release_nonlru(&freed_pvec);
|
|
continue;
|
|
|
|
activate_locked:
|
|
SetPageActive(page);
|
|
pgactivate++;
|
|
keep_locked:
|
|
unlock_page(page);
|
|
keep:
|
|
list_add(&page->lru, &ret_pages);
|
|
BUG_ON(PageLRU(page));
|
|
}
|
|
list_splice(&ret_pages, page_list);
|
|
if (pagevec_count(&freed_pvec))
|
|
__pagevec_release_nonlru(&freed_pvec);
|
|
mod_page_state(pgactivate, pgactivate);
|
|
sc->nr_reclaimed += reclaimed;
|
|
return reclaimed;
|
|
}
|
|
|
|
#ifdef CONFIG_MIGRATION
|
|
static inline void move_to_lru(struct page *page)
|
|
{
|
|
list_del(&page->lru);
|
|
if (PageActive(page)) {
|
|
/*
|
|
* lru_cache_add_active checks that
|
|
* the PG_active bit is off.
|
|
*/
|
|
ClearPageActive(page);
|
|
lru_cache_add_active(page);
|
|
} else {
|
|
lru_cache_add(page);
|
|
}
|
|
put_page(page);
|
|
}
|
|
|
|
/*
|
|
* Add isolated pages on the list back to the LRU.
|
|
*
|
|
* returns the number of pages put back.
|
|
*/
|
|
int putback_lru_pages(struct list_head *l)
|
|
{
|
|
struct page *page;
|
|
struct page *page2;
|
|
int count = 0;
|
|
|
|
list_for_each_entry_safe(page, page2, l, lru) {
|
|
move_to_lru(page);
|
|
count++;
|
|
}
|
|
return count;
|
|
}
|
|
|
|
/*
|
|
* Non migratable page
|
|
*/
|
|
int fail_migrate_page(struct page *newpage, struct page *page)
|
|
{
|
|
return -EIO;
|
|
}
|
|
EXPORT_SYMBOL(fail_migrate_page);
|
|
|
|
/*
|
|
* swapout a single page
|
|
* page is locked upon entry, unlocked on exit
|
|
*/
|
|
static int swap_page(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
|
|
if (page_mapped(page) && mapping)
|
|
if (try_to_unmap(page, 1) != SWAP_SUCCESS)
|
|
goto unlock_retry;
|
|
|
|
if (PageDirty(page)) {
|
|
/* Page is dirty, try to write it out here */
|
|
switch(pageout(page, mapping)) {
|
|
case PAGE_KEEP:
|
|
case PAGE_ACTIVATE:
|
|
goto unlock_retry;
|
|
|
|
case PAGE_SUCCESS:
|
|
goto retry;
|
|
|
|
case PAGE_CLEAN:
|
|
; /* try to free the page below */
|
|
}
|
|
}
|
|
|
|
if (PagePrivate(page)) {
|
|
if (!try_to_release_page(page, GFP_KERNEL) ||
|
|
(!mapping && page_count(page) == 1))
|
|
goto unlock_retry;
|
|
}
|
|
|
|
if (remove_mapping(mapping, page)) {
|
|
/* Success */
|
|
unlock_page(page);
|
|
return 0;
|
|
}
|
|
|
|
unlock_retry:
|
|
unlock_page(page);
|
|
|
|
retry:
|
|
return -EAGAIN;
|
|
}
|
|
EXPORT_SYMBOL(swap_page);
|
|
|
|
/*
|
|
* Page migration was first developed in the context of the memory hotplug
|
|
* project. The main authors of the migration code are:
|
|
*
|
|
* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
|
|
* Hirokazu Takahashi <taka@valinux.co.jp>
|
|
* Dave Hansen <haveblue@us.ibm.com>
|
|
* Christoph Lameter <clameter@sgi.com>
|
|
*/
|
|
|
|
/*
|
|
* Remove references for a page and establish the new page with the correct
|
|
* basic settings to be able to stop accesses to the page.
|
|
*/
|
|
int migrate_page_remove_references(struct page *newpage,
|
|
struct page *page, int nr_refs)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
struct page **radix_pointer;
|
|
|
|
/*
|
|
* Avoid doing any of the following work if the page count
|
|
* indicates that the page is in use or truncate has removed
|
|
* the page.
|
|
*/
|
|
if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
|
|
return -EAGAIN;
|
|
|
|
/*
|
|
* Establish swap ptes for anonymous pages or destroy pte
|
|
* maps for files.
|
|
*
|
|
* In order to reestablish file backed mappings the fault handlers
|
|
* will take the radix tree_lock which may then be used to stop
|
|
* processses from accessing this page until the new page is ready.
|
|
*
|
|
* A process accessing via a swap pte (an anonymous page) will take a
|
|
* page_lock on the old page which will block the process until the
|
|
* migration attempt is complete. At that time the PageSwapCache bit
|
|
* will be examined. If the page was migrated then the PageSwapCache
|
|
* bit will be clear and the operation to retrieve the page will be
|
|
* retried which will find the new page in the radix tree. Then a new
|
|
* direct mapping may be generated based on the radix tree contents.
|
|
*
|
|
* If the page was not migrated then the PageSwapCache bit
|
|
* is still set and the operation may continue.
|
|
*/
|
|
if (try_to_unmap(page, 1) == SWAP_FAIL)
|
|
/* A vma has VM_LOCKED set -> Permanent failure */
|
|
return -EPERM;
|
|
|
|
/*
|
|
* Give up if we were unable to remove all mappings.
|
|
*/
|
|
if (page_mapcount(page))
|
|
return -EAGAIN;
|
|
|
|
write_lock_irq(&mapping->tree_lock);
|
|
|
|
radix_pointer = (struct page **)radix_tree_lookup_slot(
|
|
&mapping->page_tree,
|
|
page_index(page));
|
|
|
|
if (!page_mapping(page) || page_count(page) != nr_refs ||
|
|
*radix_pointer != page) {
|
|
write_unlock_irq(&mapping->tree_lock);
|
|
return -EAGAIN;
|
|
}
|
|
|
|
/*
|
|
* Now we know that no one else is looking at the page.
|
|
*
|
|
* Certain minimal information about a page must be available
|
|
* in order for other subsystems to properly handle the page if they
|
|
* find it through the radix tree update before we are finished
|
|
* copying the page.
|
|
*/
|
|
get_page(newpage);
|
|
newpage->index = page->index;
|
|
newpage->mapping = page->mapping;
|
|
if (PageSwapCache(page)) {
|
|
SetPageSwapCache(newpage);
|
|
set_page_private(newpage, page_private(page));
|
|
}
|
|
|
|
*radix_pointer = newpage;
|
|
__put_page(page);
|
|
write_unlock_irq(&mapping->tree_lock);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(migrate_page_remove_references);
|
|
|
|
/*
|
|
* Copy the page to its new location
|
|
*/
|
|
void migrate_page_copy(struct page *newpage, struct page *page)
|
|
{
|
|
copy_highpage(newpage, page);
|
|
|
|
if (PageError(page))
|
|
SetPageError(newpage);
|
|
if (PageReferenced(page))
|
|
SetPageReferenced(newpage);
|
|
if (PageUptodate(page))
|
|
SetPageUptodate(newpage);
|
|
if (PageActive(page))
|
|
SetPageActive(newpage);
|
|
if (PageChecked(page))
|
|
SetPageChecked(newpage);
|
|
if (PageMappedToDisk(page))
|
|
SetPageMappedToDisk(newpage);
|
|
|
|
if (PageDirty(page)) {
|
|
clear_page_dirty_for_io(page);
|
|
set_page_dirty(newpage);
|
|
}
|
|
|
|
ClearPageSwapCache(page);
|
|
ClearPageActive(page);
|
|
ClearPagePrivate(page);
|
|
set_page_private(page, 0);
|
|
page->mapping = NULL;
|
|
|
|
/*
|
|
* If any waiters have accumulated on the new page then
|
|
* wake them up.
|
|
*/
|
|
if (PageWriteback(newpage))
|
|
end_page_writeback(newpage);
|
|
}
|
|
EXPORT_SYMBOL(migrate_page_copy);
|
|
|
|
/*
|
|
* Common logic to directly migrate a single page suitable for
|
|
* pages that do not use PagePrivate.
|
|
*
|
|
* Pages are locked upon entry and exit.
|
|
*/
|
|
int migrate_page(struct page *newpage, struct page *page)
|
|
{
|
|
int rc;
|
|
|
|
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
|
|
|
|
rc = migrate_page_remove_references(newpage, page, 2);
|
|
|
|
if (rc)
|
|
return rc;
|
|
|
|
migrate_page_copy(newpage, page);
|
|
|
|
/*
|
|
* Remove auxiliary swap entries and replace
|
|
* them with real ptes.
|
|
*
|
|
* Note that a real pte entry will allow processes that are not
|
|
* waiting on the page lock to use the new page via the page tables
|
|
* before the new page is unlocked.
|
|
*/
|
|
remove_from_swap(newpage);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(migrate_page);
|
|
|
|
/*
|
|
* migrate_pages
|
|
*
|
|
* Two lists are passed to this function. The first list
|
|
* contains the pages isolated from the LRU to be migrated.
|
|
* The second list contains new pages that the pages isolated
|
|
* can be moved to. If the second list is NULL then all
|
|
* pages are swapped out.
|
|
*
|
|
* The function returns after 10 attempts or if no pages
|
|
* are movable anymore because to has become empty
|
|
* or no retryable pages exist anymore.
|
|
*
|
|
* Return: Number of pages not migrated when "to" ran empty.
|
|
*/
|
|
int migrate_pages(struct list_head *from, struct list_head *to,
|
|
struct list_head *moved, struct list_head *failed)
|
|
{
|
|
int retry;
|
|
int nr_failed = 0;
|
|
int pass = 0;
|
|
struct page *page;
|
|
struct page *page2;
|
|
int swapwrite = current->flags & PF_SWAPWRITE;
|
|
int rc;
|
|
|
|
if (!swapwrite)
|
|
current->flags |= PF_SWAPWRITE;
|
|
|
|
redo:
|
|
retry = 0;
|
|
|
|
list_for_each_entry_safe(page, page2, from, lru) {
|
|
struct page *newpage = NULL;
|
|
struct address_space *mapping;
|
|
|
|
cond_resched();
|
|
|
|
rc = 0;
|
|
if (page_count(page) == 1)
|
|
/* page was freed from under us. So we are done. */
|
|
goto next;
|
|
|
|
if (to && list_empty(to))
|
|
break;
|
|
|
|
/*
|
|
* Skip locked pages during the first two passes to give the
|
|
* functions holding the lock time to release the page. Later we
|
|
* use lock_page() to have a higher chance of acquiring the
|
|
* lock.
|
|
*/
|
|
rc = -EAGAIN;
|
|
if (pass > 2)
|
|
lock_page(page);
|
|
else
|
|
if (TestSetPageLocked(page))
|
|
goto next;
|
|
|
|
/*
|
|
* Only wait on writeback if we have already done a pass where
|
|
* we we may have triggered writeouts for lots of pages.
|
|
*/
|
|
if (pass > 0) {
|
|
wait_on_page_writeback(page);
|
|
} else {
|
|
if (PageWriteback(page))
|
|
goto unlock_page;
|
|
}
|
|
|
|
/*
|
|
* Anonymous pages must have swap cache references otherwise
|
|
* the information contained in the page maps cannot be
|
|
* preserved.
|
|
*/
|
|
if (PageAnon(page) && !PageSwapCache(page)) {
|
|
if (!add_to_swap(page, GFP_KERNEL)) {
|
|
rc = -ENOMEM;
|
|
goto unlock_page;
|
|
}
|
|
}
|
|
|
|
if (!to) {
|
|
rc = swap_page(page);
|
|
goto next;
|
|
}
|
|
|
|
newpage = lru_to_page(to);
|
|
lock_page(newpage);
|
|
|
|
/*
|
|
* Pages are properly locked and writeback is complete.
|
|
* Try to migrate the page.
|
|
*/
|
|
mapping = page_mapping(page);
|
|
if (!mapping)
|
|
goto unlock_both;
|
|
|
|
if (mapping->a_ops->migratepage) {
|
|
/*
|
|
* Most pages have a mapping and most filesystems
|
|
* should provide a migration function. Anonymous
|
|
* pages are part of swap space which also has its
|
|
* own migration function. This is the most common
|
|
* path for page migration.
|
|
*/
|
|
rc = mapping->a_ops->migratepage(newpage, page);
|
|
goto unlock_both;
|
|
}
|
|
|
|
/*
|
|
* Default handling if a filesystem does not provide
|
|
* a migration function. We can only migrate clean
|
|
* pages so try to write out any dirty pages first.
|
|
*/
|
|
if (PageDirty(page)) {
|
|
switch (pageout(page, mapping)) {
|
|
case PAGE_KEEP:
|
|
case PAGE_ACTIVATE:
|
|
goto unlock_both;
|
|
|
|
case PAGE_SUCCESS:
|
|
unlock_page(newpage);
|
|
goto next;
|
|
|
|
case PAGE_CLEAN:
|
|
; /* try to migrate the page below */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Buffers are managed in a filesystem specific way.
|
|
* We must have no buffers or drop them.
|
|
*/
|
|
if (!page_has_buffers(page) ||
|
|
try_to_release_page(page, GFP_KERNEL)) {
|
|
rc = migrate_page(newpage, page);
|
|
goto unlock_both;
|
|
}
|
|
|
|
/*
|
|
* On early passes with mapped pages simply
|
|
* retry. There may be a lock held for some
|
|
* buffers that may go away. Later
|
|
* swap them out.
|
|
*/
|
|
if (pass > 4) {
|
|
/*
|
|
* Persistently unable to drop buffers..... As a
|
|
* measure of last resort we fall back to
|
|
* swap_page().
|
|
*/
|
|
unlock_page(newpage);
|
|
newpage = NULL;
|
|
rc = swap_page(page);
|
|
goto next;
|
|
}
|
|
|
|
unlock_both:
|
|
unlock_page(newpage);
|
|
|
|
unlock_page:
|
|
unlock_page(page);
|
|
|
|
next:
|
|
if (rc == -EAGAIN) {
|
|
retry++;
|
|
} else if (rc) {
|
|
/* Permanent failure */
|
|
list_move(&page->lru, failed);
|
|
nr_failed++;
|
|
} else {
|
|
if (newpage) {
|
|
/* Successful migration. Return page to LRU */
|
|
move_to_lru(newpage);
|
|
}
|
|
list_move(&page->lru, moved);
|
|
}
|
|
}
|
|
if (retry && pass++ < 10)
|
|
goto redo;
|
|
|
|
if (!swapwrite)
|
|
current->flags &= ~PF_SWAPWRITE;
|
|
|
|
return nr_failed + retry;
|
|
}
|
|
|
|
/*
|
|
* Isolate one page from the LRU lists and put it on the
|
|
* indicated list with elevated refcount.
|
|
*
|
|
* Result:
|
|
* 0 = page not on LRU list
|
|
* 1 = page removed from LRU list and added to the specified list.
|
|
*/
|
|
int isolate_lru_page(struct page *page)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (PageLRU(page)) {
|
|
struct zone *zone = page_zone(page);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
if (TestClearPageLRU(page)) {
|
|
ret = 1;
|
|
get_page(page);
|
|
if (PageActive(page))
|
|
del_page_from_active_list(zone, page);
|
|
else
|
|
del_page_from_inactive_list(zone, page);
|
|
}
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* zone->lru_lock is heavily contended. Some of the functions that
|
|
* shrink the lists perform better by taking out a batch of pages
|
|
* and working on them outside the LRU lock.
|
|
*
|
|
* For pagecache intensive workloads, this function is the hottest
|
|
* spot in the kernel (apart from copy_*_user functions).
|
|
*
|
|
* Appropriate locks must be held before calling this function.
|
|
*
|
|
* @nr_to_scan: The number of pages to look through on the list.
|
|
* @src: The LRU list to pull pages off.
|
|
* @dst: The temp list to put pages on to.
|
|
* @scanned: The number of pages that were scanned.
|
|
*
|
|
* returns how many pages were moved onto *@dst.
|
|
*/
|
|
static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
|
|
struct list_head *dst, int *scanned)
|
|
{
|
|
int nr_taken = 0;
|
|
struct page *page;
|
|
int scan = 0;
|
|
|
|
while (scan++ < nr_to_scan && !list_empty(src)) {
|
|
page = lru_to_page(src);
|
|
prefetchw_prev_lru_page(page, src, flags);
|
|
|
|
if (!TestClearPageLRU(page))
|
|
BUG();
|
|
list_del(&page->lru);
|
|
if (get_page_testone(page)) {
|
|
/*
|
|
* It is being freed elsewhere
|
|
*/
|
|
__put_page(page);
|
|
SetPageLRU(page);
|
|
list_add(&page->lru, src);
|
|
continue;
|
|
} else {
|
|
list_add(&page->lru, dst);
|
|
nr_taken++;
|
|
}
|
|
}
|
|
|
|
*scanned = scan;
|
|
return nr_taken;
|
|
}
|
|
|
|
/*
|
|
* shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
|
|
*/
|
|
static void shrink_cache(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
LIST_HEAD(page_list);
|
|
struct pagevec pvec;
|
|
int max_scan = sc->nr_to_scan;
|
|
|
|
pagevec_init(&pvec, 1);
|
|
|
|
lru_add_drain();
|
|
spin_lock_irq(&zone->lru_lock);
|
|
while (max_scan > 0) {
|
|
struct page *page;
|
|
int nr_taken;
|
|
int nr_scan;
|
|
int nr_freed;
|
|
|
|
nr_taken = isolate_lru_pages(sc->swap_cluster_max,
|
|
&zone->inactive_list,
|
|
&page_list, &nr_scan);
|
|
zone->nr_inactive -= nr_taken;
|
|
zone->pages_scanned += nr_scan;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
|
|
if (nr_taken == 0)
|
|
goto done;
|
|
|
|
max_scan -= nr_scan;
|
|
nr_freed = shrink_list(&page_list, sc);
|
|
|
|
local_irq_disable();
|
|
if (current_is_kswapd()) {
|
|
__mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
|
|
__mod_page_state(kswapd_steal, nr_freed);
|
|
} else
|
|
__mod_page_state_zone(zone, pgscan_direct, nr_scan);
|
|
__mod_page_state_zone(zone, pgsteal, nr_freed);
|
|
|
|
spin_lock(&zone->lru_lock);
|
|
/*
|
|
* Put back any unfreeable pages.
|
|
*/
|
|
while (!list_empty(&page_list)) {
|
|
page = lru_to_page(&page_list);
|
|
if (TestSetPageLRU(page))
|
|
BUG();
|
|
list_del(&page->lru);
|
|
if (PageActive(page))
|
|
add_page_to_active_list(zone, page);
|
|
else
|
|
add_page_to_inactive_list(zone, page);
|
|
if (!pagevec_add(&pvec, page)) {
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
__pagevec_release(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
}
|
|
}
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
done:
|
|
pagevec_release(&pvec);
|
|
}
|
|
|
|
/*
|
|
* This moves pages from the active list to the inactive list.
|
|
*
|
|
* We move them the other way if the page is referenced by one or more
|
|
* processes, from rmap.
|
|
*
|
|
* If the pages are mostly unmapped, the processing is fast and it is
|
|
* appropriate to hold zone->lru_lock across the whole operation. But if
|
|
* the pages are mapped, the processing is slow (page_referenced()) so we
|
|
* should drop zone->lru_lock around each page. It's impossible to balance
|
|
* this, so instead we remove the pages from the LRU while processing them.
|
|
* It is safe to rely on PG_active against the non-LRU pages in here because
|
|
* nobody will play with that bit on a non-LRU page.
|
|
*
|
|
* The downside is that we have to touch page->_count against each page.
|
|
* But we had to alter page->flags anyway.
|
|
*/
|
|
static void
|
|
refill_inactive_zone(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
int pgmoved;
|
|
int pgdeactivate = 0;
|
|
int pgscanned;
|
|
int nr_pages = sc->nr_to_scan;
|
|
LIST_HEAD(l_hold); /* The pages which were snipped off */
|
|
LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
|
|
LIST_HEAD(l_active); /* Pages to go onto the active_list */
|
|
struct page *page;
|
|
struct pagevec pvec;
|
|
int reclaim_mapped = 0;
|
|
|
|
if (unlikely(sc->may_swap)) {
|
|
long mapped_ratio;
|
|
long distress;
|
|
long swap_tendency;
|
|
|
|
/*
|
|
* `distress' is a measure of how much trouble we're having
|
|
* reclaiming pages. 0 -> no problems. 100 -> great trouble.
|
|
*/
|
|
distress = 100 >> zone->prev_priority;
|
|
|
|
/*
|
|
* The point of this algorithm is to decide when to start
|
|
* reclaiming mapped memory instead of just pagecache. Work out
|
|
* how much memory
|
|
* is mapped.
|
|
*/
|
|
mapped_ratio = (sc->nr_mapped * 100) / total_memory;
|
|
|
|
/*
|
|
* Now decide how much we really want to unmap some pages. The
|
|
* mapped ratio is downgraded - just because there's a lot of
|
|
* mapped memory doesn't necessarily mean that page reclaim
|
|
* isn't succeeding.
|
|
*
|
|
* The distress ratio is important - we don't want to start
|
|
* going oom.
|
|
*
|
|
* A 100% value of vm_swappiness overrides this algorithm
|
|
* altogether.
|
|
*/
|
|
swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
|
|
|
|
/*
|
|
* Now use this metric to decide whether to start moving mapped
|
|
* memory onto the inactive list.
|
|
*/
|
|
if (swap_tendency >= 100)
|
|
reclaim_mapped = 1;
|
|
}
|
|
|
|
lru_add_drain();
|
|
spin_lock_irq(&zone->lru_lock);
|
|
pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
|
|
&l_hold, &pgscanned);
|
|
zone->pages_scanned += pgscanned;
|
|
zone->nr_active -= pgmoved;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
|
|
while (!list_empty(&l_hold)) {
|
|
cond_resched();
|
|
page = lru_to_page(&l_hold);
|
|
list_del(&page->lru);
|
|
if (page_mapped(page)) {
|
|
if (!reclaim_mapped ||
|
|
(total_swap_pages == 0 && PageAnon(page)) ||
|
|
page_referenced(page, 0)) {
|
|
list_add(&page->lru, &l_active);
|
|
continue;
|
|
}
|
|
}
|
|
list_add(&page->lru, &l_inactive);
|
|
}
|
|
|
|
pagevec_init(&pvec, 1);
|
|
pgmoved = 0;
|
|
spin_lock_irq(&zone->lru_lock);
|
|
while (!list_empty(&l_inactive)) {
|
|
page = lru_to_page(&l_inactive);
|
|
prefetchw_prev_lru_page(page, &l_inactive, flags);
|
|
if (TestSetPageLRU(page))
|
|
BUG();
|
|
if (!TestClearPageActive(page))
|
|
BUG();
|
|
list_move(&page->lru, &zone->inactive_list);
|
|
pgmoved++;
|
|
if (!pagevec_add(&pvec, page)) {
|
|
zone->nr_inactive += pgmoved;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
pgdeactivate += pgmoved;
|
|
pgmoved = 0;
|
|
if (buffer_heads_over_limit)
|
|
pagevec_strip(&pvec);
|
|
__pagevec_release(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
}
|
|
zone->nr_inactive += pgmoved;
|
|
pgdeactivate += pgmoved;
|
|
if (buffer_heads_over_limit) {
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
pagevec_strip(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
|
|
pgmoved = 0;
|
|
while (!list_empty(&l_active)) {
|
|
page = lru_to_page(&l_active);
|
|
prefetchw_prev_lru_page(page, &l_active, flags);
|
|
if (TestSetPageLRU(page))
|
|
BUG();
|
|
BUG_ON(!PageActive(page));
|
|
list_move(&page->lru, &zone->active_list);
|
|
pgmoved++;
|
|
if (!pagevec_add(&pvec, page)) {
|
|
zone->nr_active += pgmoved;
|
|
pgmoved = 0;
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
__pagevec_release(&pvec);
|
|
spin_lock_irq(&zone->lru_lock);
|
|
}
|
|
}
|
|
zone->nr_active += pgmoved;
|
|
spin_unlock(&zone->lru_lock);
|
|
|
|
__mod_page_state_zone(zone, pgrefill, pgscanned);
|
|
__mod_page_state(pgdeactivate, pgdeactivate);
|
|
local_irq_enable();
|
|
|
|
pagevec_release(&pvec);
|
|
}
|
|
|
|
/*
|
|
* This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
|
|
*/
|
|
static void
|
|
shrink_zone(struct zone *zone, struct scan_control *sc)
|
|
{
|
|
unsigned long nr_active;
|
|
unsigned long nr_inactive;
|
|
|
|
atomic_inc(&zone->reclaim_in_progress);
|
|
|
|
/*
|
|
* Add one to `nr_to_scan' just to make sure that the kernel will
|
|
* slowly sift through the active list.
|
|
*/
|
|
zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
|
|
nr_active = zone->nr_scan_active;
|
|
if (nr_active >= sc->swap_cluster_max)
|
|
zone->nr_scan_active = 0;
|
|
else
|
|
nr_active = 0;
|
|
|
|
zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
|
|
nr_inactive = zone->nr_scan_inactive;
|
|
if (nr_inactive >= sc->swap_cluster_max)
|
|
zone->nr_scan_inactive = 0;
|
|
else
|
|
nr_inactive = 0;
|
|
|
|
while (nr_active || nr_inactive) {
|
|
if (nr_active) {
|
|
sc->nr_to_scan = min(nr_active,
|
|
(unsigned long)sc->swap_cluster_max);
|
|
nr_active -= sc->nr_to_scan;
|
|
refill_inactive_zone(zone, sc);
|
|
}
|
|
|
|
if (nr_inactive) {
|
|
sc->nr_to_scan = min(nr_inactive,
|
|
(unsigned long)sc->swap_cluster_max);
|
|
nr_inactive -= sc->nr_to_scan;
|
|
shrink_cache(zone, sc);
|
|
}
|
|
}
|
|
|
|
throttle_vm_writeout();
|
|
|
|
atomic_dec(&zone->reclaim_in_progress);
|
|
}
|
|
|
|
/*
|
|
* This is the direct reclaim path, for page-allocating processes. We only
|
|
* try to reclaim pages from zones which will satisfy the caller's allocation
|
|
* request.
|
|
*
|
|
* We reclaim from a zone even if that zone is over pages_high. Because:
|
|
* a) The caller may be trying to free *extra* pages to satisfy a higher-order
|
|
* allocation or
|
|
* b) The zones may be over pages_high but they must go *over* pages_high to
|
|
* satisfy the `incremental min' zone defense algorithm.
|
|
*
|
|
* Returns the number of reclaimed pages.
|
|
*
|
|
* If a zone is deemed to be full of pinned pages then just give it a light
|
|
* scan then give up on it.
|
|
*/
|
|
static void
|
|
shrink_caches(struct zone **zones, struct scan_control *sc)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; zones[i] != NULL; i++) {
|
|
struct zone *zone = zones[i];
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
continue;
|
|
|
|
zone->temp_priority = sc->priority;
|
|
if (zone->prev_priority > sc->priority)
|
|
zone->prev_priority = sc->priority;
|
|
|
|
if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
|
|
continue; /* Let kswapd poll it */
|
|
|
|
shrink_zone(zone, sc);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is the main entry point to direct page reclaim.
|
|
*
|
|
* If a full scan of the inactive list fails to free enough memory then we
|
|
* are "out of memory" and something needs to be killed.
|
|
*
|
|
* If the caller is !__GFP_FS then the probability of a failure is reasonably
|
|
* high - the zone may be full of dirty or under-writeback pages, which this
|
|
* caller can't do much about. We kick pdflush and take explicit naps in the
|
|
* hope that some of these pages can be written. But if the allocating task
|
|
* holds filesystem locks which prevent writeout this might not work, and the
|
|
* allocation attempt will fail.
|
|
*/
|
|
int try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
|
|
{
|
|
int priority;
|
|
int ret = 0;
|
|
int total_scanned = 0, total_reclaimed = 0;
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
struct scan_control sc;
|
|
unsigned long lru_pages = 0;
|
|
int i;
|
|
|
|
sc.gfp_mask = gfp_mask;
|
|
sc.may_writepage = !laptop_mode;
|
|
sc.may_swap = 1;
|
|
|
|
inc_page_state(allocstall);
|
|
|
|
for (i = 0; zones[i] != NULL; i++) {
|
|
struct zone *zone = zones[i];
|
|
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
continue;
|
|
|
|
zone->temp_priority = DEF_PRIORITY;
|
|
lru_pages += zone->nr_active + zone->nr_inactive;
|
|
}
|
|
|
|
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
|
|
sc.nr_mapped = read_page_state(nr_mapped);
|
|
sc.nr_scanned = 0;
|
|
sc.nr_reclaimed = 0;
|
|
sc.priority = priority;
|
|
sc.swap_cluster_max = SWAP_CLUSTER_MAX;
|
|
if (!priority)
|
|
disable_swap_token();
|
|
shrink_caches(zones, &sc);
|
|
shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
|
|
if (reclaim_state) {
|
|
sc.nr_reclaimed += reclaim_state->reclaimed_slab;
|
|
reclaim_state->reclaimed_slab = 0;
|
|
}
|
|
total_scanned += sc.nr_scanned;
|
|
total_reclaimed += sc.nr_reclaimed;
|
|
if (total_reclaimed >= sc.swap_cluster_max) {
|
|
ret = 1;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Try to write back as many pages as we just scanned. This
|
|
* tends to cause slow streaming writers to write data to the
|
|
* disk smoothly, at the dirtying rate, which is nice. But
|
|
* that's undesirable in laptop mode, where we *want* lumpy
|
|
* writeout. So in laptop mode, write out the whole world.
|
|
*/
|
|
if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
|
|
wakeup_pdflush(laptop_mode ? 0 : total_scanned);
|
|
sc.may_writepage = 1;
|
|
}
|
|
|
|
/* Take a nap, wait for some writeback to complete */
|
|
if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
|
|
blk_congestion_wait(WRITE, HZ/10);
|
|
}
|
|
out:
|
|
for (i = 0; zones[i] != 0; i++) {
|
|
struct zone *zone = zones[i];
|
|
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
continue;
|
|
|
|
zone->prev_priority = zone->temp_priority;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* For kswapd, balance_pgdat() will work across all this node's zones until
|
|
* they are all at pages_high.
|
|
*
|
|
* If `nr_pages' is non-zero then it is the number of pages which are to be
|
|
* reclaimed, regardless of the zone occupancies. This is a software suspend
|
|
* special.
|
|
*
|
|
* Returns the number of pages which were actually freed.
|
|
*
|
|
* There is special handling here for zones which are full of pinned pages.
|
|
* This can happen if the pages are all mlocked, or if they are all used by
|
|
* device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
|
|
* What we do is to detect the case where all pages in the zone have been
|
|
* scanned twice and there has been zero successful reclaim. Mark the zone as
|
|
* dead and from now on, only perform a short scan. Basically we're polling
|
|
* the zone for when the problem goes away.
|
|
*
|
|
* kswapd scans the zones in the highmem->normal->dma direction. It skips
|
|
* zones which have free_pages > pages_high, but once a zone is found to have
|
|
* free_pages <= pages_high, we scan that zone and the lower zones regardless
|
|
* of the number of free pages in the lower zones. This interoperates with
|
|
* the page allocator fallback scheme to ensure that aging of pages is balanced
|
|
* across the zones.
|
|
*/
|
|
static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
|
|
{
|
|
int to_free = nr_pages;
|
|
int all_zones_ok;
|
|
int priority;
|
|
int i;
|
|
int total_scanned, total_reclaimed;
|
|
struct reclaim_state *reclaim_state = current->reclaim_state;
|
|
struct scan_control sc;
|
|
|
|
loop_again:
|
|
total_scanned = 0;
|
|
total_reclaimed = 0;
|
|
sc.gfp_mask = GFP_KERNEL;
|
|
sc.may_writepage = !laptop_mode;
|
|
sc.may_swap = 1;
|
|
sc.nr_mapped = read_page_state(nr_mapped);
|
|
|
|
inc_page_state(pageoutrun);
|
|
|
|
for (i = 0; i < pgdat->nr_zones; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
zone->temp_priority = DEF_PRIORITY;
|
|
}
|
|
|
|
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
|
|
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
|
|
unsigned long lru_pages = 0;
|
|
|
|
/* The swap token gets in the way of swapout... */
|
|
if (!priority)
|
|
disable_swap_token();
|
|
|
|
all_zones_ok = 1;
|
|
|
|
if (nr_pages == 0) {
|
|
/*
|
|
* Scan in the highmem->dma direction for the highest
|
|
* zone which needs scanning
|
|
*/
|
|
for (i = pgdat->nr_zones - 1; i >= 0; i--) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (zone->all_unreclaimable &&
|
|
priority != DEF_PRIORITY)
|
|
continue;
|
|
|
|
if (!zone_watermark_ok(zone, order,
|
|
zone->pages_high, 0, 0)) {
|
|
end_zone = i;
|
|
goto scan;
|
|
}
|
|
}
|
|
goto out;
|
|
} else {
|
|
end_zone = pgdat->nr_zones - 1;
|
|
}
|
|
scan:
|
|
for (i = 0; i <= end_zone; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
lru_pages += zone->nr_active + zone->nr_inactive;
|
|
}
|
|
|
|
/*
|
|
* Now scan the zone in the dma->highmem direction, stopping
|
|
* at the last zone which needs scanning.
|
|
*
|
|
* We do this because the page allocator works in the opposite
|
|
* direction. This prevents the page allocator from allocating
|
|
* pages behind kswapd's direction of progress, which would
|
|
* cause too much scanning of the lower zones.
|
|
*/
|
|
for (i = 0; i <= end_zone; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
int nr_slab;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
|
|
continue;
|
|
|
|
if (nr_pages == 0) { /* Not software suspend */
|
|
if (!zone_watermark_ok(zone, order,
|
|
zone->pages_high, end_zone, 0))
|
|
all_zones_ok = 0;
|
|
}
|
|
zone->temp_priority = priority;
|
|
if (zone->prev_priority > priority)
|
|
zone->prev_priority = priority;
|
|
sc.nr_scanned = 0;
|
|
sc.nr_reclaimed = 0;
|
|
sc.priority = priority;
|
|
sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
|
|
shrink_zone(zone, &sc);
|
|
reclaim_state->reclaimed_slab = 0;
|
|
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
|
|
lru_pages);
|
|
sc.nr_reclaimed += reclaim_state->reclaimed_slab;
|
|
total_reclaimed += sc.nr_reclaimed;
|
|
total_scanned += sc.nr_scanned;
|
|
if (zone->all_unreclaimable)
|
|
continue;
|
|
if (nr_slab == 0 && zone->pages_scanned >=
|
|
(zone->nr_active + zone->nr_inactive) * 4)
|
|
zone->all_unreclaimable = 1;
|
|
/*
|
|
* If we've done a decent amount of scanning and
|
|
* the reclaim ratio is low, start doing writepage
|
|
* even in laptop mode
|
|
*/
|
|
if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
|
|
total_scanned > total_reclaimed+total_reclaimed/2)
|
|
sc.may_writepage = 1;
|
|
}
|
|
if (nr_pages && to_free > total_reclaimed)
|
|
continue; /* swsusp: need to do more work */
|
|
if (all_zones_ok)
|
|
break; /* kswapd: all done */
|
|
/*
|
|
* OK, kswapd is getting into trouble. Take a nap, then take
|
|
* another pass across the zones.
|
|
*/
|
|
if (total_scanned && priority < DEF_PRIORITY - 2)
|
|
blk_congestion_wait(WRITE, HZ/10);
|
|
|
|
/*
|
|
* We do this so kswapd doesn't build up large priorities for
|
|
* example when it is freeing in parallel with allocators. It
|
|
* matches the direct reclaim path behaviour in terms of impact
|
|
* on zone->*_priority.
|
|
*/
|
|
if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
|
|
break;
|
|
}
|
|
out:
|
|
for (i = 0; i < pgdat->nr_zones; i++) {
|
|
struct zone *zone = pgdat->node_zones + i;
|
|
|
|
zone->prev_priority = zone->temp_priority;
|
|
}
|
|
if (!all_zones_ok) {
|
|
cond_resched();
|
|
goto loop_again;
|
|
}
|
|
|
|
return total_reclaimed;
|
|
}
|
|
|
|
/*
|
|
* The background pageout daemon, started as a kernel thread
|
|
* from the init process.
|
|
*
|
|
* This basically trickles out pages so that we have _some_
|
|
* free memory available even if there is no other activity
|
|
* that frees anything up. This is needed for things like routing
|
|
* etc, where we otherwise might have all activity going on in
|
|
* asynchronous contexts that cannot page things out.
|
|
*
|
|
* If there are applications that are active memory-allocators
|
|
* (most normal use), this basically shouldn't matter.
|
|
*/
|
|
static int kswapd(void *p)
|
|
{
|
|
unsigned long order;
|
|
pg_data_t *pgdat = (pg_data_t*)p;
|
|
struct task_struct *tsk = current;
|
|
DEFINE_WAIT(wait);
|
|
struct reclaim_state reclaim_state = {
|
|
.reclaimed_slab = 0,
|
|
};
|
|
cpumask_t cpumask;
|
|
|
|
daemonize("kswapd%d", pgdat->node_id);
|
|
cpumask = node_to_cpumask(pgdat->node_id);
|
|
if (!cpus_empty(cpumask))
|
|
set_cpus_allowed(tsk, cpumask);
|
|
current->reclaim_state = &reclaim_state;
|
|
|
|
/*
|
|
* Tell the memory management that we're a "memory allocator",
|
|
* and that if we need more memory we should get access to it
|
|
* regardless (see "__alloc_pages()"). "kswapd" should
|
|
* never get caught in the normal page freeing logic.
|
|
*
|
|
* (Kswapd normally doesn't need memory anyway, but sometimes
|
|
* you need a small amount of memory in order to be able to
|
|
* page out something else, and this flag essentially protects
|
|
* us from recursively trying to free more memory as we're
|
|
* trying to free the first piece of memory in the first place).
|
|
*/
|
|
tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
|
|
|
|
order = 0;
|
|
for ( ; ; ) {
|
|
unsigned long new_order;
|
|
|
|
try_to_freeze();
|
|
|
|
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
|
|
new_order = pgdat->kswapd_max_order;
|
|
pgdat->kswapd_max_order = 0;
|
|
if (order < new_order) {
|
|
/*
|
|
* Don't sleep if someone wants a larger 'order'
|
|
* allocation
|
|
*/
|
|
order = new_order;
|
|
} else {
|
|
schedule();
|
|
order = pgdat->kswapd_max_order;
|
|
}
|
|
finish_wait(&pgdat->kswapd_wait, &wait);
|
|
|
|
balance_pgdat(pgdat, 0, order);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* A zone is low on free memory, so wake its kswapd task to service it.
|
|
*/
|
|
void wakeup_kswapd(struct zone *zone, int order)
|
|
{
|
|
pg_data_t *pgdat;
|
|
|
|
if (!populated_zone(zone))
|
|
return;
|
|
|
|
pgdat = zone->zone_pgdat;
|
|
if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
|
|
return;
|
|
if (pgdat->kswapd_max_order < order)
|
|
pgdat->kswapd_max_order = order;
|
|
if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
|
|
return;
|
|
if (!waitqueue_active(&pgdat->kswapd_wait))
|
|
return;
|
|
wake_up_interruptible(&pgdat->kswapd_wait);
|
|
}
|
|
|
|
#ifdef CONFIG_PM
|
|
/*
|
|
* Try to free `nr_pages' of memory, system-wide. Returns the number of freed
|
|
* pages.
|
|
*/
|
|
int shrink_all_memory(int nr_pages)
|
|
{
|
|
pg_data_t *pgdat;
|
|
int nr_to_free = nr_pages;
|
|
int ret = 0;
|
|
struct reclaim_state reclaim_state = {
|
|
.reclaimed_slab = 0,
|
|
};
|
|
|
|
current->reclaim_state = &reclaim_state;
|
|
for_each_pgdat(pgdat) {
|
|
int freed;
|
|
freed = balance_pgdat(pgdat, nr_to_free, 0);
|
|
ret += freed;
|
|
nr_to_free -= freed;
|
|
if (nr_to_free <= 0)
|
|
break;
|
|
}
|
|
current->reclaim_state = NULL;
|
|
return ret;
|
|
}
|
|
#endif
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
/* It's optimal to keep kswapds on the same CPUs as their memory, but
|
|
not required for correctness. So if the last cpu in a node goes
|
|
away, we get changed to run anywhere: as the first one comes back,
|
|
restore their cpu bindings. */
|
|
static int __devinit cpu_callback(struct notifier_block *nfb,
|
|
unsigned long action,
|
|
void *hcpu)
|
|
{
|
|
pg_data_t *pgdat;
|
|
cpumask_t mask;
|
|
|
|
if (action == CPU_ONLINE) {
|
|
for_each_pgdat(pgdat) {
|
|
mask = node_to_cpumask(pgdat->node_id);
|
|
if (any_online_cpu(mask) != NR_CPUS)
|
|
/* One of our CPUs online: restore mask */
|
|
set_cpus_allowed(pgdat->kswapd, mask);
|
|
}
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
#endif /* CONFIG_HOTPLUG_CPU */
|
|
|
|
static int __init kswapd_init(void)
|
|
{
|
|
pg_data_t *pgdat;
|
|
swap_setup();
|
|
for_each_pgdat(pgdat)
|
|
pgdat->kswapd
|
|
= find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
|
|
total_memory = nr_free_pagecache_pages();
|
|
hotcpu_notifier(cpu_callback, 0);
|
|
return 0;
|
|
}
|
|
|
|
module_init(kswapd_init)
|
|
|
|
#ifdef CONFIG_NUMA
|
|
/*
|
|
* Zone reclaim mode
|
|
*
|
|
* If non-zero call zone_reclaim when the number of free pages falls below
|
|
* the watermarks.
|
|
*
|
|
* In the future we may add flags to the mode. However, the page allocator
|
|
* should only have to check that zone_reclaim_mode != 0 before calling
|
|
* zone_reclaim().
|
|
*/
|
|
int zone_reclaim_mode __read_mostly;
|
|
|
|
#define RECLAIM_OFF 0
|
|
#define RECLAIM_ZONE (1<<0) /* Run shrink_cache on the zone */
|
|
#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
|
|
#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
|
|
#define RECLAIM_SLAB (1<<3) /* Do a global slab shrink if the zone is out of memory */
|
|
|
|
/*
|
|
* Mininum time between zone reclaim scans
|
|
*/
|
|
int zone_reclaim_interval __read_mostly = 30*HZ;
|
|
|
|
/*
|
|
* Priority for ZONE_RECLAIM. This determines the fraction of pages
|
|
* of a node considered for each zone_reclaim. 4 scans 1/16th of
|
|
* a zone.
|
|
*/
|
|
#define ZONE_RECLAIM_PRIORITY 4
|
|
|
|
/*
|
|
* Try to free up some pages from this zone through reclaim.
|
|
*/
|
|
int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
|
|
{
|
|
int nr_pages;
|
|
struct task_struct *p = current;
|
|
struct reclaim_state reclaim_state;
|
|
struct scan_control sc;
|
|
cpumask_t mask;
|
|
int node_id;
|
|
|
|
if (time_before(jiffies,
|
|
zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval))
|
|
return 0;
|
|
|
|
if (!(gfp_mask & __GFP_WAIT) ||
|
|
zone->all_unreclaimable ||
|
|
atomic_read(&zone->reclaim_in_progress) > 0 ||
|
|
(p->flags & PF_MEMALLOC))
|
|
return 0;
|
|
|
|
node_id = zone->zone_pgdat->node_id;
|
|
mask = node_to_cpumask(node_id);
|
|
if (!cpus_empty(mask) && node_id != numa_node_id())
|
|
return 0;
|
|
|
|
sc.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE);
|
|
sc.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP);
|
|
sc.nr_scanned = 0;
|
|
sc.nr_reclaimed = 0;
|
|
sc.priority = ZONE_RECLAIM_PRIORITY + 1;
|
|
sc.nr_mapped = read_page_state(nr_mapped);
|
|
sc.gfp_mask = gfp_mask;
|
|
|
|
disable_swap_token();
|
|
|
|
nr_pages = 1 << order;
|
|
if (nr_pages > SWAP_CLUSTER_MAX)
|
|
sc.swap_cluster_max = nr_pages;
|
|
else
|
|
sc.swap_cluster_max = SWAP_CLUSTER_MAX;
|
|
|
|
cond_resched();
|
|
/*
|
|
* We need to be able to allocate from the reserves for RECLAIM_SWAP
|
|
* and we also need to be able to write out pages for RECLAIM_WRITE
|
|
* and RECLAIM_SWAP.
|
|
*/
|
|
p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
|
|
reclaim_state.reclaimed_slab = 0;
|
|
p->reclaim_state = &reclaim_state;
|
|
|
|
/*
|
|
* Free memory by calling shrink zone with increasing priorities
|
|
* until we have enough memory freed.
|
|
*/
|
|
do {
|
|
sc.priority--;
|
|
shrink_zone(zone, &sc);
|
|
|
|
} while (sc.nr_reclaimed < nr_pages && sc.priority > 0);
|
|
|
|
if (sc.nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) {
|
|
/*
|
|
* shrink_slab does not currently allow us to determine
|
|
* how many pages were freed in the zone. So we just
|
|
* shake the slab and then go offnode for a single allocation.
|
|
*
|
|
* shrink_slab will free memory on all zones and may take
|
|
* a long time.
|
|
*/
|
|
shrink_slab(sc.nr_scanned, gfp_mask, order);
|
|
}
|
|
|
|
p->reclaim_state = NULL;
|
|
current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
|
|
|
|
if (sc.nr_reclaimed == 0)
|
|
zone->last_unsuccessful_zone_reclaim = jiffies;
|
|
|
|
return sc.nr_reclaimed >= nr_pages;
|
|
}
|
|
#endif
|
|
|