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![Chen Wandun](/assets/img/avatar_default.png)
In unset_migratetype_isolate(), we can bypass the call to
move_freepages_block() for non-buddy pages.
It will save a few cpu cycles for some situations such as cma and
hugetlb when allocating continue pages, in these situation function
alloc_contig_pages will be called.
alloc_contig_pages
__alloc_contig_migrate_range
isolate_freepages_range ==> pages has been remove from buddy
undo_isolate_page_range
unset_migratetype_isolate ==> can directly set migratetype
[osalvador@suse.de: changelog tweak]
Link: https://lkml.kernel.org/r/20211229033649.2760586-1-chenwandun@huawei.com
Fixes: 3c605096d3
("mm/page_alloc: restrict max order of merging on isolated pageblock")
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
306 lines
9.1 KiB
C
306 lines
9.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/page_isolation.c
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*/
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#include <linux/mm.h>
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#include <linux/page-isolation.h>
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#include <linux/pageblock-flags.h>
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#include <linux/memory.h>
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#include <linux/hugetlb.h>
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#include <linux/page_owner.h>
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#include <linux/migrate.h>
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#include "internal.h"
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#define CREATE_TRACE_POINTS
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#include <trace/events/page_isolation.h>
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static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
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{
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struct zone *zone = page_zone(page);
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struct page *unmovable;
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unsigned long flags;
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spin_lock_irqsave(&zone->lock, flags);
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/*
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* We assume the caller intended to SET migrate type to isolate.
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* If it is already set, then someone else must have raced and
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* set it before us.
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*/
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if (is_migrate_isolate_page(page)) {
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spin_unlock_irqrestore(&zone->lock, flags);
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return -EBUSY;
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}
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/*
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* FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
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* We just check MOVABLE pages.
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*/
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unmovable = has_unmovable_pages(zone, page, migratetype, isol_flags);
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if (!unmovable) {
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unsigned long nr_pages;
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int mt = get_pageblock_migratetype(page);
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set_pageblock_migratetype(page, MIGRATE_ISOLATE);
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zone->nr_isolate_pageblock++;
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nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
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NULL);
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__mod_zone_freepage_state(zone, -nr_pages, mt);
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spin_unlock_irqrestore(&zone->lock, flags);
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return 0;
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}
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spin_unlock_irqrestore(&zone->lock, flags);
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if (isol_flags & REPORT_FAILURE) {
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/*
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* printk() with zone->lock held will likely trigger a
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* lockdep splat, so defer it here.
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*/
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dump_page(unmovable, "unmovable page");
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}
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return -EBUSY;
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}
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static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
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{
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struct zone *zone;
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unsigned long flags, nr_pages;
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bool isolated_page = false;
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unsigned int order;
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unsigned long pfn, buddy_pfn;
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struct page *buddy;
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zone = page_zone(page);
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spin_lock_irqsave(&zone->lock, flags);
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if (!is_migrate_isolate_page(page))
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goto out;
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/*
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* Because freepage with more than pageblock_order on isolated
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* pageblock is restricted to merge due to freepage counting problem,
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* it is possible that there is free buddy page.
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* move_freepages_block() doesn't care of merge so we need other
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* approach in order to merge them. Isolation and free will make
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* these pages to be merged.
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*/
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if (PageBuddy(page)) {
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order = buddy_order(page);
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if (order >= pageblock_order && order < MAX_ORDER - 1) {
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pfn = page_to_pfn(page);
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buddy_pfn = __find_buddy_pfn(pfn, order);
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buddy = page + (buddy_pfn - pfn);
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if (!is_migrate_isolate_page(buddy)) {
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isolated_page = !!__isolate_free_page(page, order);
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/*
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* Isolating a free page in an isolated pageblock
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* is expected to always work as watermarks don't
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* apply here.
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*/
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VM_WARN_ON(!isolated_page);
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}
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}
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}
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/*
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* If we isolate freepage with more than pageblock_order, there
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* should be no freepage in the range, so we could avoid costly
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* pageblock scanning for freepage moving.
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*
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* We didn't actually touch any of the isolated pages, so place them
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* to the tail of the freelist. This is an optimization for memory
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* onlining - just onlined memory won't immediately be considered for
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* allocation.
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*/
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if (!isolated_page && PageBuddy(page)) {
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nr_pages = move_freepages_block(zone, page, migratetype, NULL);
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__mod_zone_freepage_state(zone, nr_pages, migratetype);
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}
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set_pageblock_migratetype(page, migratetype);
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if (isolated_page)
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__putback_isolated_page(page, order, migratetype);
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zone->nr_isolate_pageblock--;
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out:
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spin_unlock_irqrestore(&zone->lock, flags);
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}
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static inline struct page *
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__first_valid_page(unsigned long pfn, unsigned long nr_pages)
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{
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int i;
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for (i = 0; i < nr_pages; i++) {
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struct page *page;
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page = pfn_to_online_page(pfn + i);
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if (!page)
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continue;
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return page;
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}
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return NULL;
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}
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/**
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* start_isolate_page_range() - make page-allocation-type of range of pages to
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* be MIGRATE_ISOLATE.
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* @start_pfn: The lower PFN of the range to be isolated.
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* @end_pfn: The upper PFN of the range to be isolated.
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* start_pfn/end_pfn must be aligned to pageblock_order.
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* @migratetype: Migrate type to set in error recovery.
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* @flags: The following flags are allowed (they can be combined in
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* a bit mask)
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* MEMORY_OFFLINE - isolate to offline (!allocate) memory
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* e.g., skip over PageHWPoison() pages
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* and PageOffline() pages.
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* REPORT_FAILURE - report details about the failure to
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* isolate the range
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*
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* Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
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* the range will never be allocated. Any free pages and pages freed in the
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* future will not be allocated again. If specified range includes migrate types
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* other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all
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* pages in the range finally, the caller have to free all pages in the range.
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* test_page_isolated() can be used for test it.
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*
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* There is no high level synchronization mechanism that prevents two threads
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* from trying to isolate overlapping ranges. If this happens, one thread
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* will notice pageblocks in the overlapping range already set to isolate.
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* This happens in set_migratetype_isolate, and set_migratetype_isolate
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* returns an error. We then clean up by restoring the migration type on
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* pageblocks we may have modified and return -EBUSY to caller. This
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* prevents two threads from simultaneously working on overlapping ranges.
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*
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* Please note that there is no strong synchronization with the page allocator
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* either. Pages might be freed while their page blocks are marked ISOLATED.
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* A call to drain_all_pages() after isolation can flush most of them. However
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* in some cases pages might still end up on pcp lists and that would allow
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* for their allocation even when they are in fact isolated already. Depending
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* on how strong of a guarantee the caller needs, zone_pcp_disable/enable()
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* might be used to flush and disable pcplist before isolation and enable after
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* unisolation.
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*
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* Return: 0 on success and -EBUSY if any part of range cannot be isolated.
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*/
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int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
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unsigned migratetype, int flags)
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{
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unsigned long pfn;
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struct page *page;
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BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
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BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
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for (pfn = start_pfn;
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pfn < end_pfn;
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pfn += pageblock_nr_pages) {
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page = __first_valid_page(pfn, pageblock_nr_pages);
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if (page && set_migratetype_isolate(page, migratetype, flags)) {
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undo_isolate_page_range(start_pfn, pfn, migratetype);
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return -EBUSY;
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}
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}
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return 0;
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}
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/*
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* Make isolated pages available again.
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*/
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void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
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unsigned migratetype)
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{
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unsigned long pfn;
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struct page *page;
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BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
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BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
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for (pfn = start_pfn;
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pfn < end_pfn;
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pfn += pageblock_nr_pages) {
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page = __first_valid_page(pfn, pageblock_nr_pages);
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if (!page || !is_migrate_isolate_page(page))
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continue;
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unset_migratetype_isolate(page, migratetype);
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}
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}
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/*
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* Test all pages in the range is free(means isolated) or not.
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* all pages in [start_pfn...end_pfn) must be in the same zone.
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* zone->lock must be held before call this.
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*
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* Returns the last tested pfn.
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*/
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static unsigned long
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__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
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int flags)
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{
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struct page *page;
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while (pfn < end_pfn) {
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page = pfn_to_page(pfn);
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if (PageBuddy(page))
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/*
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* If the page is on a free list, it has to be on
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* the correct MIGRATE_ISOLATE freelist. There is no
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* simple way to verify that as VM_BUG_ON(), though.
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*/
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pfn += 1 << buddy_order(page);
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else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
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/* A HWPoisoned page cannot be also PageBuddy */
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pfn++;
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else if ((flags & MEMORY_OFFLINE) && PageOffline(page) &&
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!page_count(page))
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/*
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* The responsible driver agreed to skip PageOffline()
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* pages when offlining memory by dropping its
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* reference in MEM_GOING_OFFLINE.
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*/
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pfn++;
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else
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break;
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}
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return pfn;
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}
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/* Caller should ensure that requested range is in a single zone */
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int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
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int isol_flags)
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{
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unsigned long pfn, flags;
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struct page *page;
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struct zone *zone;
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int ret;
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/*
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* Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
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* are not aligned to pageblock_nr_pages.
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* Then we just check migratetype first.
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*/
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for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
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page = __first_valid_page(pfn, pageblock_nr_pages);
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if (page && !is_migrate_isolate_page(page))
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break;
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}
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page = __first_valid_page(start_pfn, end_pfn - start_pfn);
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if ((pfn < end_pfn) || !page) {
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ret = -EBUSY;
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goto out;
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}
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/* Check all pages are free or marked as ISOLATED */
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zone = page_zone(page);
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spin_lock_irqsave(&zone->lock, flags);
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pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, isol_flags);
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spin_unlock_irqrestore(&zone->lock, flags);
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ret = pfn < end_pfn ? -EBUSY : 0;
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out:
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trace_test_pages_isolated(start_pfn, end_pfn, pfn);
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return ret;
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}
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