mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-25 02:09:42 +00:00
![Mel Gorman](/assets/img/avatar_default.png)
aops->write_begin may allocate a new page and make it visible only to have mark_page_accessed called almost immediately after. Once the page is visible the atomic operations are necessary which is noticable overhead when writing to an in-memory filesystem like tmpfs but should also be noticable with fast storage. The objective of the patch is to initialse the accessed information with non-atomic operations before the page is visible. The bulk of filesystems directly or indirectly use grab_cache_page_write_begin or find_or_create_page for the initial allocation of a page cache page. This patch adds an init_page_accessed() helper which behaves like the first call to mark_page_accessed() but may called before the page is visible and can be done non-atomically. The primary APIs of concern in this care are the following and are used by most filesystems. find_get_page find_lock_page find_or_create_page grab_cache_page_nowait grab_cache_page_write_begin All of them are very similar in detail to the patch creates a core helper pagecache_get_page() which takes a flags parameter that affects its behavior such as whether the page should be marked accessed or not. Then old API is preserved but is basically a thin wrapper around this core function. Each of the filesystems are then updated to avoid calling mark_page_accessed when it is known that the VM interfaces have already done the job. There is a slight snag in that the timing of the mark_page_accessed() has now changed so in rare cases it's possible a page gets to the end of the LRU as PageReferenced where as previously it might have been repromoted. This is expected to be rare but it's worth the filesystem people thinking about it in case they see a problem with the timing change. It is also the case that some filesystems may be marking pages accessed that previously did not but it makes sense that filesystems have consistent behaviour in this regard. The test case used to evaulate this is a simple dd of a large file done multiple times with the file deleted on each iterations. The size of the file is 1/10th physical memory to avoid dirty page balancing. In the async case it will be possible that the workload completes without even hitting the disk and will have variable results but highlight the impact of mark_page_accessed for async IO. The sync results are expected to be more stable. The exception is tmpfs where the normal case is for the "IO" to not hit the disk. The test machine was single socket and UMA to avoid any scheduling or NUMA artifacts. Throughput and wall times are presented for sync IO, only wall times are shown for async as the granularity reported by dd and the variability is unsuitable for comparison. As async results were variable do to writback timings, I'm only reporting the maximum figures. The sync results were stable enough to make the mean and stddev uninteresting. The performance results are reported based on a run with no profiling. Profile data is based on a separate run with oprofile running. async dd 3.15.0-rc3 3.15.0-rc3 vanilla accessed-v2 ext3 Max elapsed 13.9900 ( 0.00%) 11.5900 ( 17.16%) tmpfs Max elapsed 0.5100 ( 0.00%) 0.4900 ( 3.92%) btrfs Max elapsed 12.8100 ( 0.00%) 12.7800 ( 0.23%) ext4 Max elapsed 18.6000 ( 0.00%) 13.3400 ( 28.28%) xfs Max elapsed 12.5600 ( 0.00%) 2.0900 ( 83.36%) The XFS figure is a bit strange as it managed to avoid a worst case by sheer luck but the average figures looked reasonable. samples percentage ext3 86107 0.9783 vmlinux-3.15.0-rc4-vanilla mark_page_accessed ext3 23833 0.2710 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed ext3 5036 0.0573 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed ext4 64566 0.8961 vmlinux-3.15.0-rc4-vanilla mark_page_accessed ext4 5322 0.0713 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed ext4 2869 0.0384 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed xfs 62126 1.7675 vmlinux-3.15.0-rc4-vanilla mark_page_accessed xfs 1904 0.0554 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed xfs 103 0.0030 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed btrfs 10655 0.1338 vmlinux-3.15.0-rc4-vanilla mark_page_accessed btrfs 2020 0.0273 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed btrfs 587 0.0079 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed tmpfs 59562 3.2628 vmlinux-3.15.0-rc4-vanilla mark_page_accessed tmpfs 1210 0.0696 vmlinux-3.15.0-rc4-accessed-v3r25 init_page_accessed tmpfs 94 0.0054 vmlinux-3.15.0-rc4-accessed-v3r25 mark_page_accessed [akpm@linux-foundation.org: don't run init_page_accessed() against an uninitialised pointer] Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Jan Kara <jack@suse.cz> Cc: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Theodore Ts'o <tytso@mit.edu> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Tested-by: Prabhakar Lad <prabhakar.csengg@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1122 lines
31 KiB
C
1122 lines
31 KiB
C
/*
|
|
* linux/mm/swap.c
|
|
*
|
|
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
|
|
*/
|
|
|
|
/*
|
|
* This file contains the default values for the operation of the
|
|
* Linux VM subsystem. Fine-tuning documentation can be found in
|
|
* Documentation/sysctl/vm.txt.
|
|
* Started 18.12.91
|
|
* Swap aging added 23.2.95, Stephen Tweedie.
|
|
* Buffermem limits added 12.3.98, Rik van Riel.
|
|
*/
|
|
|
|
#include <linux/mm.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/kernel_stat.h>
|
|
#include <linux/swap.h>
|
|
#include <linux/mman.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/pagevec.h>
|
|
#include <linux/init.h>
|
|
#include <linux/export.h>
|
|
#include <linux/mm_inline.h>
|
|
#include <linux/percpu_counter.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/notifier.h>
|
|
#include <linux/backing-dev.h>
|
|
#include <linux/memcontrol.h>
|
|
#include <linux/gfp.h>
|
|
#include <linux/uio.h>
|
|
|
|
#include "internal.h"
|
|
|
|
#define CREATE_TRACE_POINTS
|
|
#include <trace/events/pagemap.h>
|
|
|
|
/* How many pages do we try to swap or page in/out together? */
|
|
int page_cluster;
|
|
|
|
static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
|
|
static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
|
|
static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
|
|
|
|
/*
|
|
* This path almost never happens for VM activity - pages are normally
|
|
* freed via pagevecs. But it gets used by networking.
|
|
*/
|
|
static void __page_cache_release(struct page *page)
|
|
{
|
|
if (PageLRU(page)) {
|
|
struct zone *zone = page_zone(page);
|
|
struct lruvec *lruvec;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&zone->lru_lock, flags);
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
VM_BUG_ON_PAGE(!PageLRU(page), page);
|
|
__ClearPageLRU(page);
|
|
del_page_from_lru_list(page, lruvec, page_off_lru(page));
|
|
spin_unlock_irqrestore(&zone->lru_lock, flags);
|
|
}
|
|
}
|
|
|
|
static void __put_single_page(struct page *page)
|
|
{
|
|
__page_cache_release(page);
|
|
free_hot_cold_page(page, false);
|
|
}
|
|
|
|
static void __put_compound_page(struct page *page)
|
|
{
|
|
compound_page_dtor *dtor;
|
|
|
|
__page_cache_release(page);
|
|
dtor = get_compound_page_dtor(page);
|
|
(*dtor)(page);
|
|
}
|
|
|
|
/**
|
|
* Two special cases here: we could avoid taking compound_lock_irqsave
|
|
* and could skip the tail refcounting(in _mapcount).
|
|
*
|
|
* 1. Hugetlbfs page:
|
|
*
|
|
* PageHeadHuge will remain true until the compound page
|
|
* is released and enters the buddy allocator, and it could
|
|
* not be split by __split_huge_page_refcount().
|
|
*
|
|
* So if we see PageHeadHuge set, and we have the tail page pin,
|
|
* then we could safely put head page.
|
|
*
|
|
* 2. Slab THP page:
|
|
*
|
|
* PG_slab is cleared before the slab frees the head page, and
|
|
* tail pin cannot be the last reference left on the head page,
|
|
* because the slab code is free to reuse the compound page
|
|
* after a kfree/kmem_cache_free without having to check if
|
|
* there's any tail pin left. In turn all tail pinsmust be always
|
|
* released while the head is still pinned by the slab code
|
|
* and so we know PG_slab will be still set too.
|
|
*
|
|
* So if we see PageSlab set, and we have the tail page pin,
|
|
* then we could safely put head page.
|
|
*/
|
|
static __always_inline
|
|
void put_unrefcounted_compound_page(struct page *page_head, struct page *page)
|
|
{
|
|
/*
|
|
* If @page is a THP tail, we must read the tail page
|
|
* flags after the head page flags. The
|
|
* __split_huge_page_refcount side enforces write memory barriers
|
|
* between clearing PageTail and before the head page
|
|
* can be freed and reallocated.
|
|
*/
|
|
smp_rmb();
|
|
if (likely(PageTail(page))) {
|
|
/*
|
|
* __split_huge_page_refcount cannot race
|
|
* here, see the comment above this function.
|
|
*/
|
|
VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
|
|
VM_BUG_ON_PAGE(page_mapcount(page) != 0, page);
|
|
if (put_page_testzero(page_head)) {
|
|
/*
|
|
* If this is the tail of a slab THP page,
|
|
* the tail pin must not be the last reference
|
|
* held on the page, because the PG_slab cannot
|
|
* be cleared before all tail pins (which skips
|
|
* the _mapcount tail refcounting) have been
|
|
* released.
|
|
*
|
|
* If this is the tail of a hugetlbfs page,
|
|
* the tail pin may be the last reference on
|
|
* the page instead, because PageHeadHuge will
|
|
* not go away until the compound page enters
|
|
* the buddy allocator.
|
|
*/
|
|
VM_BUG_ON_PAGE(PageSlab(page_head), page_head);
|
|
__put_compound_page(page_head);
|
|
}
|
|
} else
|
|
/*
|
|
* __split_huge_page_refcount run before us,
|
|
* @page was a THP tail. The split @page_head
|
|
* has been freed and reallocated as slab or
|
|
* hugetlbfs page of smaller order (only
|
|
* possible if reallocated as slab on x86).
|
|
*/
|
|
if (put_page_testzero(page))
|
|
__put_single_page(page);
|
|
}
|
|
|
|
static __always_inline
|
|
void put_refcounted_compound_page(struct page *page_head, struct page *page)
|
|
{
|
|
if (likely(page != page_head && get_page_unless_zero(page_head))) {
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* @page_head wasn't a dangling pointer but it may not
|
|
* be a head page anymore by the time we obtain the
|
|
* lock. That is ok as long as it can't be freed from
|
|
* under us.
|
|
*/
|
|
flags = compound_lock_irqsave(page_head);
|
|
if (unlikely(!PageTail(page))) {
|
|
/* __split_huge_page_refcount run before us */
|
|
compound_unlock_irqrestore(page_head, flags);
|
|
if (put_page_testzero(page_head)) {
|
|
/*
|
|
* The @page_head may have been freed
|
|
* and reallocated as a compound page
|
|
* of smaller order and then freed
|
|
* again. All we know is that it
|
|
* cannot have become: a THP page, a
|
|
* compound page of higher order, a
|
|
* tail page. That is because we
|
|
* still hold the refcount of the
|
|
* split THP tail and page_head was
|
|
* the THP head before the split.
|
|
*/
|
|
if (PageHead(page_head))
|
|
__put_compound_page(page_head);
|
|
else
|
|
__put_single_page(page_head);
|
|
}
|
|
out_put_single:
|
|
if (put_page_testzero(page))
|
|
__put_single_page(page);
|
|
return;
|
|
}
|
|
VM_BUG_ON_PAGE(page_head != page->first_page, page);
|
|
/*
|
|
* We can release the refcount taken by
|
|
* get_page_unless_zero() now that
|
|
* __split_huge_page_refcount() is blocked on the
|
|
* compound_lock.
|
|
*/
|
|
if (put_page_testzero(page_head))
|
|
VM_BUG_ON_PAGE(1, page_head);
|
|
/* __split_huge_page_refcount will wait now */
|
|
VM_BUG_ON_PAGE(page_mapcount(page) <= 0, page);
|
|
atomic_dec(&page->_mapcount);
|
|
VM_BUG_ON_PAGE(atomic_read(&page_head->_count) <= 0, page_head);
|
|
VM_BUG_ON_PAGE(atomic_read(&page->_count) != 0, page);
|
|
compound_unlock_irqrestore(page_head, flags);
|
|
|
|
if (put_page_testzero(page_head)) {
|
|
if (PageHead(page_head))
|
|
__put_compound_page(page_head);
|
|
else
|
|
__put_single_page(page_head);
|
|
}
|
|
} else {
|
|
/* @page_head is a dangling pointer */
|
|
VM_BUG_ON_PAGE(PageTail(page), page);
|
|
goto out_put_single;
|
|
}
|
|
}
|
|
|
|
static void put_compound_page(struct page *page)
|
|
{
|
|
struct page *page_head;
|
|
|
|
/*
|
|
* We see the PageCompound set and PageTail not set, so @page maybe:
|
|
* 1. hugetlbfs head page, or
|
|
* 2. THP head page.
|
|
*/
|
|
if (likely(!PageTail(page))) {
|
|
if (put_page_testzero(page)) {
|
|
/*
|
|
* By the time all refcounts have been released
|
|
* split_huge_page cannot run anymore from under us.
|
|
*/
|
|
if (PageHead(page))
|
|
__put_compound_page(page);
|
|
else
|
|
__put_single_page(page);
|
|
}
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* We see the PageCompound set and PageTail set, so @page maybe:
|
|
* 1. a tail hugetlbfs page, or
|
|
* 2. a tail THP page, or
|
|
* 3. a split THP page.
|
|
*
|
|
* Case 3 is possible, as we may race with
|
|
* __split_huge_page_refcount tearing down a THP page.
|
|
*/
|
|
page_head = compound_head_by_tail(page);
|
|
if (!__compound_tail_refcounted(page_head))
|
|
put_unrefcounted_compound_page(page_head, page);
|
|
else
|
|
put_refcounted_compound_page(page_head, page);
|
|
}
|
|
|
|
void put_page(struct page *page)
|
|
{
|
|
if (unlikely(PageCompound(page)))
|
|
put_compound_page(page);
|
|
else if (put_page_testzero(page))
|
|
__put_single_page(page);
|
|
}
|
|
EXPORT_SYMBOL(put_page);
|
|
|
|
/*
|
|
* This function is exported but must not be called by anything other
|
|
* than get_page(). It implements the slow path of get_page().
|
|
*/
|
|
bool __get_page_tail(struct page *page)
|
|
{
|
|
/*
|
|
* This takes care of get_page() if run on a tail page
|
|
* returned by one of the get_user_pages/follow_page variants.
|
|
* get_user_pages/follow_page itself doesn't need the compound
|
|
* lock because it runs __get_page_tail_foll() under the
|
|
* proper PT lock that already serializes against
|
|
* split_huge_page().
|
|
*/
|
|
unsigned long flags;
|
|
bool got;
|
|
struct page *page_head = compound_head(page);
|
|
|
|
/* Ref to put_compound_page() comment. */
|
|
if (!__compound_tail_refcounted(page_head)) {
|
|
smp_rmb();
|
|
if (likely(PageTail(page))) {
|
|
/*
|
|
* This is a hugetlbfs page or a slab
|
|
* page. __split_huge_page_refcount
|
|
* cannot race here.
|
|
*/
|
|
VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
|
|
__get_page_tail_foll(page, true);
|
|
return true;
|
|
} else {
|
|
/*
|
|
* __split_huge_page_refcount run
|
|
* before us, "page" was a THP
|
|
* tail. The split page_head has been
|
|
* freed and reallocated as slab or
|
|
* hugetlbfs page of smaller order
|
|
* (only possible if reallocated as
|
|
* slab on x86).
|
|
*/
|
|
return false;
|
|
}
|
|
}
|
|
|
|
got = false;
|
|
if (likely(page != page_head && get_page_unless_zero(page_head))) {
|
|
/*
|
|
* page_head wasn't a dangling pointer but it
|
|
* may not be a head page anymore by the time
|
|
* we obtain the lock. That is ok as long as it
|
|
* can't be freed from under us.
|
|
*/
|
|
flags = compound_lock_irqsave(page_head);
|
|
/* here __split_huge_page_refcount won't run anymore */
|
|
if (likely(PageTail(page))) {
|
|
__get_page_tail_foll(page, false);
|
|
got = true;
|
|
}
|
|
compound_unlock_irqrestore(page_head, flags);
|
|
if (unlikely(!got))
|
|
put_page(page_head);
|
|
}
|
|
return got;
|
|
}
|
|
EXPORT_SYMBOL(__get_page_tail);
|
|
|
|
/**
|
|
* put_pages_list() - release a list of pages
|
|
* @pages: list of pages threaded on page->lru
|
|
*
|
|
* Release a list of pages which are strung together on page.lru. Currently
|
|
* used by read_cache_pages() and related error recovery code.
|
|
*/
|
|
void put_pages_list(struct list_head *pages)
|
|
{
|
|
while (!list_empty(pages)) {
|
|
struct page *victim;
|
|
|
|
victim = list_entry(pages->prev, struct page, lru);
|
|
list_del(&victim->lru);
|
|
page_cache_release(victim);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(put_pages_list);
|
|
|
|
/*
|
|
* get_kernel_pages() - pin kernel pages in memory
|
|
* @kiov: An array of struct kvec structures
|
|
* @nr_segs: number of segments to pin
|
|
* @write: pinning for read/write, currently ignored
|
|
* @pages: array that receives pointers to the pages pinned.
|
|
* Should be at least nr_segs long.
|
|
*
|
|
* Returns number of pages pinned. This may be fewer than the number
|
|
* requested. If nr_pages is 0 or negative, returns 0. If no pages
|
|
* were pinned, returns -errno. Each page returned must be released
|
|
* with a put_page() call when it is finished with.
|
|
*/
|
|
int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
|
|
struct page **pages)
|
|
{
|
|
int seg;
|
|
|
|
for (seg = 0; seg < nr_segs; seg++) {
|
|
if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
|
|
return seg;
|
|
|
|
pages[seg] = kmap_to_page(kiov[seg].iov_base);
|
|
page_cache_get(pages[seg]);
|
|
}
|
|
|
|
return seg;
|
|
}
|
|
EXPORT_SYMBOL_GPL(get_kernel_pages);
|
|
|
|
/*
|
|
* get_kernel_page() - pin a kernel page in memory
|
|
* @start: starting kernel address
|
|
* @write: pinning for read/write, currently ignored
|
|
* @pages: array that receives pointer to the page pinned.
|
|
* Must be at least nr_segs long.
|
|
*
|
|
* Returns 1 if page is pinned. If the page was not pinned, returns
|
|
* -errno. The page returned must be released with a put_page() call
|
|
* when it is finished with.
|
|
*/
|
|
int get_kernel_page(unsigned long start, int write, struct page **pages)
|
|
{
|
|
const struct kvec kiov = {
|
|
.iov_base = (void *)start,
|
|
.iov_len = PAGE_SIZE
|
|
};
|
|
|
|
return get_kernel_pages(&kiov, 1, write, pages);
|
|
}
|
|
EXPORT_SYMBOL_GPL(get_kernel_page);
|
|
|
|
static void pagevec_lru_move_fn(struct pagevec *pvec,
|
|
void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
|
|
void *arg)
|
|
{
|
|
int i;
|
|
struct zone *zone = NULL;
|
|
struct lruvec *lruvec;
|
|
unsigned long flags = 0;
|
|
|
|
for (i = 0; i < pagevec_count(pvec); i++) {
|
|
struct page *page = pvec->pages[i];
|
|
struct zone *pagezone = page_zone(page);
|
|
|
|
if (pagezone != zone) {
|
|
if (zone)
|
|
spin_unlock_irqrestore(&zone->lru_lock, flags);
|
|
zone = pagezone;
|
|
spin_lock_irqsave(&zone->lru_lock, flags);
|
|
}
|
|
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
(*move_fn)(page, lruvec, arg);
|
|
}
|
|
if (zone)
|
|
spin_unlock_irqrestore(&zone->lru_lock, flags);
|
|
release_pages(pvec->pages, pvec->nr, pvec->cold);
|
|
pagevec_reinit(pvec);
|
|
}
|
|
|
|
static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
|
|
void *arg)
|
|
{
|
|
int *pgmoved = arg;
|
|
|
|
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
|
|
enum lru_list lru = page_lru_base_type(page);
|
|
list_move_tail(&page->lru, &lruvec->lists[lru]);
|
|
(*pgmoved)++;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* pagevec_move_tail() must be called with IRQ disabled.
|
|
* Otherwise this may cause nasty races.
|
|
*/
|
|
static void pagevec_move_tail(struct pagevec *pvec)
|
|
{
|
|
int pgmoved = 0;
|
|
|
|
pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
|
|
__count_vm_events(PGROTATED, pgmoved);
|
|
}
|
|
|
|
/*
|
|
* Writeback is about to end against a page which has been marked for immediate
|
|
* reclaim. If it still appears to be reclaimable, move it to the tail of the
|
|
* inactive list.
|
|
*/
|
|
void rotate_reclaimable_page(struct page *page)
|
|
{
|
|
if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) &&
|
|
!PageUnevictable(page) && PageLRU(page)) {
|
|
struct pagevec *pvec;
|
|
unsigned long flags;
|
|
|
|
page_cache_get(page);
|
|
local_irq_save(flags);
|
|
pvec = this_cpu_ptr(&lru_rotate_pvecs);
|
|
if (!pagevec_add(pvec, page))
|
|
pagevec_move_tail(pvec);
|
|
local_irq_restore(flags);
|
|
}
|
|
}
|
|
|
|
static void update_page_reclaim_stat(struct lruvec *lruvec,
|
|
int file, int rotated)
|
|
{
|
|
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
|
|
|
|
reclaim_stat->recent_scanned[file]++;
|
|
if (rotated)
|
|
reclaim_stat->recent_rotated[file]++;
|
|
}
|
|
|
|
static void __activate_page(struct page *page, struct lruvec *lruvec,
|
|
void *arg)
|
|
{
|
|
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
|
|
int file = page_is_file_cache(page);
|
|
int lru = page_lru_base_type(page);
|
|
|
|
del_page_from_lru_list(page, lruvec, lru);
|
|
SetPageActive(page);
|
|
lru += LRU_ACTIVE;
|
|
add_page_to_lru_list(page, lruvec, lru);
|
|
trace_mm_lru_activate(page, page_to_pfn(page));
|
|
|
|
__count_vm_event(PGACTIVATE);
|
|
update_page_reclaim_stat(lruvec, file, 1);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
static DEFINE_PER_CPU(struct pagevec, activate_page_pvecs);
|
|
|
|
static void activate_page_drain(int cpu)
|
|
{
|
|
struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);
|
|
|
|
if (pagevec_count(pvec))
|
|
pagevec_lru_move_fn(pvec, __activate_page, NULL);
|
|
}
|
|
|
|
static bool need_activate_page_drain(int cpu)
|
|
{
|
|
return pagevec_count(&per_cpu(activate_page_pvecs, cpu)) != 0;
|
|
}
|
|
|
|
void activate_page(struct page *page)
|
|
{
|
|
if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
|
|
struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);
|
|
|
|
page_cache_get(page);
|
|
if (!pagevec_add(pvec, page))
|
|
pagevec_lru_move_fn(pvec, __activate_page, NULL);
|
|
put_cpu_var(activate_page_pvecs);
|
|
}
|
|
}
|
|
|
|
#else
|
|
static inline void activate_page_drain(int cpu)
|
|
{
|
|
}
|
|
|
|
static bool need_activate_page_drain(int cpu)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
void activate_page(struct page *page)
|
|
{
|
|
struct zone *zone = page_zone(page);
|
|
|
|
spin_lock_irq(&zone->lru_lock);
|
|
__activate_page(page, mem_cgroup_page_lruvec(page, zone), NULL);
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
}
|
|
#endif
|
|
|
|
static void __lru_cache_activate_page(struct page *page)
|
|
{
|
|
struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
|
|
int i;
|
|
|
|
/*
|
|
* Search backwards on the optimistic assumption that the page being
|
|
* activated has just been added to this pagevec. Note that only
|
|
* the local pagevec is examined as a !PageLRU page could be in the
|
|
* process of being released, reclaimed, migrated or on a remote
|
|
* pagevec that is currently being drained. Furthermore, marking
|
|
* a remote pagevec's page PageActive potentially hits a race where
|
|
* a page is marked PageActive just after it is added to the inactive
|
|
* list causing accounting errors and BUG_ON checks to trigger.
|
|
*/
|
|
for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
|
|
struct page *pagevec_page = pvec->pages[i];
|
|
|
|
if (pagevec_page == page) {
|
|
SetPageActive(page);
|
|
break;
|
|
}
|
|
}
|
|
|
|
put_cpu_var(lru_add_pvec);
|
|
}
|
|
|
|
/*
|
|
* Mark a page as having seen activity.
|
|
*
|
|
* inactive,unreferenced -> inactive,referenced
|
|
* inactive,referenced -> active,unreferenced
|
|
* active,unreferenced -> active,referenced
|
|
*/
|
|
void mark_page_accessed(struct page *page)
|
|
{
|
|
if (!PageActive(page) && !PageUnevictable(page) &&
|
|
PageReferenced(page)) {
|
|
|
|
/*
|
|
* If the page is on the LRU, queue it for activation via
|
|
* activate_page_pvecs. Otherwise, assume the page is on a
|
|
* pagevec, mark it active and it'll be moved to the active
|
|
* LRU on the next drain.
|
|
*/
|
|
if (PageLRU(page))
|
|
activate_page(page);
|
|
else
|
|
__lru_cache_activate_page(page);
|
|
ClearPageReferenced(page);
|
|
if (page_is_file_cache(page))
|
|
workingset_activation(page);
|
|
} else if (!PageReferenced(page)) {
|
|
SetPageReferenced(page);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(mark_page_accessed);
|
|
|
|
/*
|
|
* Used to mark_page_accessed(page) that is not visible yet and when it is
|
|
* still safe to use non-atomic ops
|
|
*/
|
|
void init_page_accessed(struct page *page)
|
|
{
|
|
if (!PageReferenced(page))
|
|
__SetPageReferenced(page);
|
|
}
|
|
EXPORT_SYMBOL(init_page_accessed);
|
|
|
|
static void __lru_cache_add(struct page *page)
|
|
{
|
|
struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
|
|
|
|
page_cache_get(page);
|
|
if (!pagevec_space(pvec))
|
|
__pagevec_lru_add(pvec);
|
|
pagevec_add(pvec, page);
|
|
put_cpu_var(lru_add_pvec);
|
|
}
|
|
|
|
/**
|
|
* lru_cache_add: add a page to the page lists
|
|
* @page: the page to add
|
|
*/
|
|
void lru_cache_add_anon(struct page *page)
|
|
{
|
|
if (PageActive(page))
|
|
ClearPageActive(page);
|
|
__lru_cache_add(page);
|
|
}
|
|
|
|
void lru_cache_add_file(struct page *page)
|
|
{
|
|
if (PageActive(page))
|
|
ClearPageActive(page);
|
|
__lru_cache_add(page);
|
|
}
|
|
EXPORT_SYMBOL(lru_cache_add_file);
|
|
|
|
/**
|
|
* lru_cache_add - add a page to a page list
|
|
* @page: the page to be added to the LRU.
|
|
*
|
|
* Queue the page for addition to the LRU via pagevec. The decision on whether
|
|
* to add the page to the [in]active [file|anon] list is deferred until the
|
|
* pagevec is drained. This gives a chance for the caller of lru_cache_add()
|
|
* have the page added to the active list using mark_page_accessed().
|
|
*/
|
|
void lru_cache_add(struct page *page)
|
|
{
|
|
VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
|
|
VM_BUG_ON_PAGE(PageLRU(page), page);
|
|
__lru_cache_add(page);
|
|
}
|
|
|
|
/**
|
|
* add_page_to_unevictable_list - add a page to the unevictable list
|
|
* @page: the page to be added to the unevictable list
|
|
*
|
|
* Add page directly to its zone's unevictable list. To avoid races with
|
|
* tasks that might be making the page evictable, through eg. munlock,
|
|
* munmap or exit, while it's not on the lru, we want to add the page
|
|
* while it's locked or otherwise "invisible" to other tasks. This is
|
|
* difficult to do when using the pagevec cache, so bypass that.
|
|
*/
|
|
void add_page_to_unevictable_list(struct page *page)
|
|
{
|
|
struct zone *zone = page_zone(page);
|
|
struct lruvec *lruvec;
|
|
|
|
spin_lock_irq(&zone->lru_lock);
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
ClearPageActive(page);
|
|
SetPageUnevictable(page);
|
|
SetPageLRU(page);
|
|
add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
|
|
spin_unlock_irq(&zone->lru_lock);
|
|
}
|
|
|
|
/*
|
|
* If the page can not be invalidated, it is moved to the
|
|
* inactive list to speed up its reclaim. It is moved to the
|
|
* head of the list, rather than the tail, to give the flusher
|
|
* threads some time to write it out, as this is much more
|
|
* effective than the single-page writeout from reclaim.
|
|
*
|
|
* If the page isn't page_mapped and dirty/writeback, the page
|
|
* could reclaim asap using PG_reclaim.
|
|
*
|
|
* 1. active, mapped page -> none
|
|
* 2. active, dirty/writeback page -> inactive, head, PG_reclaim
|
|
* 3. inactive, mapped page -> none
|
|
* 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
|
|
* 5. inactive, clean -> inactive, tail
|
|
* 6. Others -> none
|
|
*
|
|
* In 4, why it moves inactive's head, the VM expects the page would
|
|
* be write it out by flusher threads as this is much more effective
|
|
* than the single-page writeout from reclaim.
|
|
*/
|
|
static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
|
|
void *arg)
|
|
{
|
|
int lru, file;
|
|
bool active;
|
|
|
|
if (!PageLRU(page))
|
|
return;
|
|
|
|
if (PageUnevictable(page))
|
|
return;
|
|
|
|
/* Some processes are using the page */
|
|
if (page_mapped(page))
|
|
return;
|
|
|
|
active = PageActive(page);
|
|
file = page_is_file_cache(page);
|
|
lru = page_lru_base_type(page);
|
|
|
|
del_page_from_lru_list(page, lruvec, lru + active);
|
|
ClearPageActive(page);
|
|
ClearPageReferenced(page);
|
|
add_page_to_lru_list(page, lruvec, lru);
|
|
|
|
if (PageWriteback(page) || PageDirty(page)) {
|
|
/*
|
|
* PG_reclaim could be raced with end_page_writeback
|
|
* It can make readahead confusing. But race window
|
|
* is _really_ small and it's non-critical problem.
|
|
*/
|
|
SetPageReclaim(page);
|
|
} else {
|
|
/*
|
|
* The page's writeback ends up during pagevec
|
|
* We moves tha page into tail of inactive.
|
|
*/
|
|
list_move_tail(&page->lru, &lruvec->lists[lru]);
|
|
__count_vm_event(PGROTATED);
|
|
}
|
|
|
|
if (active)
|
|
__count_vm_event(PGDEACTIVATE);
|
|
update_page_reclaim_stat(lruvec, file, 0);
|
|
}
|
|
|
|
/*
|
|
* Drain pages out of the cpu's pagevecs.
|
|
* Either "cpu" is the current CPU, and preemption has already been
|
|
* disabled; or "cpu" is being hot-unplugged, and is already dead.
|
|
*/
|
|
void lru_add_drain_cpu(int cpu)
|
|
{
|
|
struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
|
|
|
|
if (pagevec_count(pvec))
|
|
__pagevec_lru_add(pvec);
|
|
|
|
pvec = &per_cpu(lru_rotate_pvecs, cpu);
|
|
if (pagevec_count(pvec)) {
|
|
unsigned long flags;
|
|
|
|
/* No harm done if a racing interrupt already did this */
|
|
local_irq_save(flags);
|
|
pagevec_move_tail(pvec);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
pvec = &per_cpu(lru_deactivate_pvecs, cpu);
|
|
if (pagevec_count(pvec))
|
|
pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
|
|
|
|
activate_page_drain(cpu);
|
|
}
|
|
|
|
/**
|
|
* deactivate_page - forcefully deactivate a page
|
|
* @page: page to deactivate
|
|
*
|
|
* This function hints the VM that @page is a good reclaim candidate,
|
|
* for example if its invalidation fails due to the page being dirty
|
|
* or under writeback.
|
|
*/
|
|
void deactivate_page(struct page *page)
|
|
{
|
|
/*
|
|
* In a workload with many unevictable page such as mprotect, unevictable
|
|
* page deactivation for accelerating reclaim is pointless.
|
|
*/
|
|
if (PageUnevictable(page))
|
|
return;
|
|
|
|
if (likely(get_page_unless_zero(page))) {
|
|
struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
|
|
|
|
if (!pagevec_add(pvec, page))
|
|
pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
|
|
put_cpu_var(lru_deactivate_pvecs);
|
|
}
|
|
}
|
|
|
|
void lru_add_drain(void)
|
|
{
|
|
lru_add_drain_cpu(get_cpu());
|
|
put_cpu();
|
|
}
|
|
|
|
static void lru_add_drain_per_cpu(struct work_struct *dummy)
|
|
{
|
|
lru_add_drain();
|
|
}
|
|
|
|
static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
|
|
|
|
void lru_add_drain_all(void)
|
|
{
|
|
static DEFINE_MUTEX(lock);
|
|
static struct cpumask has_work;
|
|
int cpu;
|
|
|
|
mutex_lock(&lock);
|
|
get_online_cpus();
|
|
cpumask_clear(&has_work);
|
|
|
|
for_each_online_cpu(cpu) {
|
|
struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
|
|
|
|
if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
|
|
pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
|
|
pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
|
|
need_activate_page_drain(cpu)) {
|
|
INIT_WORK(work, lru_add_drain_per_cpu);
|
|
schedule_work_on(cpu, work);
|
|
cpumask_set_cpu(cpu, &has_work);
|
|
}
|
|
}
|
|
|
|
for_each_cpu(cpu, &has_work)
|
|
flush_work(&per_cpu(lru_add_drain_work, cpu));
|
|
|
|
put_online_cpus();
|
|
mutex_unlock(&lock);
|
|
}
|
|
|
|
/*
|
|
* Batched page_cache_release(). Decrement the reference count on all the
|
|
* passed pages. If it fell to zero then remove the page from the LRU and
|
|
* free it.
|
|
*
|
|
* Avoid taking zone->lru_lock if possible, but if it is taken, retain it
|
|
* for the remainder of the operation.
|
|
*
|
|
* The locking in this function is against shrink_inactive_list(): we recheck
|
|
* the page count inside the lock to see whether shrink_inactive_list()
|
|
* grabbed the page via the LRU. If it did, give up: shrink_inactive_list()
|
|
* will free it.
|
|
*/
|
|
void release_pages(struct page **pages, int nr, bool cold)
|
|
{
|
|
int i;
|
|
LIST_HEAD(pages_to_free);
|
|
struct zone *zone = NULL;
|
|
struct lruvec *lruvec;
|
|
unsigned long uninitialized_var(flags);
|
|
|
|
for (i = 0; i < nr; i++) {
|
|
struct page *page = pages[i];
|
|
|
|
if (unlikely(PageCompound(page))) {
|
|
if (zone) {
|
|
spin_unlock_irqrestore(&zone->lru_lock, flags);
|
|
zone = NULL;
|
|
}
|
|
put_compound_page(page);
|
|
continue;
|
|
}
|
|
|
|
if (!put_page_testzero(page))
|
|
continue;
|
|
|
|
if (PageLRU(page)) {
|
|
struct zone *pagezone = page_zone(page);
|
|
|
|
if (pagezone != zone) {
|
|
if (zone)
|
|
spin_unlock_irqrestore(&zone->lru_lock,
|
|
flags);
|
|
zone = pagezone;
|
|
spin_lock_irqsave(&zone->lru_lock, flags);
|
|
}
|
|
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
VM_BUG_ON_PAGE(!PageLRU(page), page);
|
|
__ClearPageLRU(page);
|
|
del_page_from_lru_list(page, lruvec, page_off_lru(page));
|
|
}
|
|
|
|
/* Clear Active bit in case of parallel mark_page_accessed */
|
|
__ClearPageActive(page);
|
|
|
|
list_add(&page->lru, &pages_to_free);
|
|
}
|
|
if (zone)
|
|
spin_unlock_irqrestore(&zone->lru_lock, flags);
|
|
|
|
free_hot_cold_page_list(&pages_to_free, cold);
|
|
}
|
|
EXPORT_SYMBOL(release_pages);
|
|
|
|
/*
|
|
* The pages which we're about to release may be in the deferred lru-addition
|
|
* queues. That would prevent them from really being freed right now. That's
|
|
* OK from a correctness point of view but is inefficient - those pages may be
|
|
* cache-warm and we want to give them back to the page allocator ASAP.
|
|
*
|
|
* So __pagevec_release() will drain those queues here. __pagevec_lru_add()
|
|
* and __pagevec_lru_add_active() call release_pages() directly to avoid
|
|
* mutual recursion.
|
|
*/
|
|
void __pagevec_release(struct pagevec *pvec)
|
|
{
|
|
lru_add_drain();
|
|
release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
|
|
pagevec_reinit(pvec);
|
|
}
|
|
EXPORT_SYMBOL(__pagevec_release);
|
|
|
|
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
|
|
/* used by __split_huge_page_refcount() */
|
|
void lru_add_page_tail(struct page *page, struct page *page_tail,
|
|
struct lruvec *lruvec, struct list_head *list)
|
|
{
|
|
const int file = 0;
|
|
|
|
VM_BUG_ON_PAGE(!PageHead(page), page);
|
|
VM_BUG_ON_PAGE(PageCompound(page_tail), page);
|
|
VM_BUG_ON_PAGE(PageLRU(page_tail), page);
|
|
VM_BUG_ON(NR_CPUS != 1 &&
|
|
!spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
|
|
|
|
if (!list)
|
|
SetPageLRU(page_tail);
|
|
|
|
if (likely(PageLRU(page)))
|
|
list_add_tail(&page_tail->lru, &page->lru);
|
|
else if (list) {
|
|
/* page reclaim is reclaiming a huge page */
|
|
get_page(page_tail);
|
|
list_add_tail(&page_tail->lru, list);
|
|
} else {
|
|
struct list_head *list_head;
|
|
/*
|
|
* Head page has not yet been counted, as an hpage,
|
|
* so we must account for each subpage individually.
|
|
*
|
|
* Use the standard add function to put page_tail on the list,
|
|
* but then correct its position so they all end up in order.
|
|
*/
|
|
add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail));
|
|
list_head = page_tail->lru.prev;
|
|
list_move_tail(&page_tail->lru, list_head);
|
|
}
|
|
|
|
if (!PageUnevictable(page))
|
|
update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
|
|
}
|
|
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
|
|
|
|
static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
|
|
void *arg)
|
|
{
|
|
int file = page_is_file_cache(page);
|
|
int active = PageActive(page);
|
|
enum lru_list lru = page_lru(page);
|
|
|
|
VM_BUG_ON_PAGE(PageLRU(page), page);
|
|
|
|
SetPageLRU(page);
|
|
add_page_to_lru_list(page, lruvec, lru);
|
|
update_page_reclaim_stat(lruvec, file, active);
|
|
trace_mm_lru_insertion(page, page_to_pfn(page), lru, trace_pagemap_flags(page));
|
|
}
|
|
|
|
/*
|
|
* Add the passed pages to the LRU, then drop the caller's refcount
|
|
* on them. Reinitialises the caller's pagevec.
|
|
*/
|
|
void __pagevec_lru_add(struct pagevec *pvec)
|
|
{
|
|
pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
|
|
}
|
|
EXPORT_SYMBOL(__pagevec_lru_add);
|
|
|
|
/**
|
|
* pagevec_lookup_entries - gang pagecache lookup
|
|
* @pvec: Where the resulting entries are placed
|
|
* @mapping: The address_space to search
|
|
* @start: The starting entry index
|
|
* @nr_entries: The maximum number of entries
|
|
* @indices: The cache indices corresponding to the entries in @pvec
|
|
*
|
|
* pagevec_lookup_entries() will search for and return a group of up
|
|
* to @nr_entries pages and shadow entries in the mapping. All
|
|
* entries are placed in @pvec. pagevec_lookup_entries() takes a
|
|
* reference against actual pages in @pvec.
|
|
*
|
|
* The search returns a group of mapping-contiguous entries with
|
|
* ascending indexes. There may be holes in the indices due to
|
|
* not-present entries.
|
|
*
|
|
* pagevec_lookup_entries() returns the number of entries which were
|
|
* found.
|
|
*/
|
|
unsigned pagevec_lookup_entries(struct pagevec *pvec,
|
|
struct address_space *mapping,
|
|
pgoff_t start, unsigned nr_pages,
|
|
pgoff_t *indices)
|
|
{
|
|
pvec->nr = find_get_entries(mapping, start, nr_pages,
|
|
pvec->pages, indices);
|
|
return pagevec_count(pvec);
|
|
}
|
|
|
|
/**
|
|
* pagevec_remove_exceptionals - pagevec exceptionals pruning
|
|
* @pvec: The pagevec to prune
|
|
*
|
|
* pagevec_lookup_entries() fills both pages and exceptional radix
|
|
* tree entries into the pagevec. This function prunes all
|
|
* exceptionals from @pvec without leaving holes, so that it can be
|
|
* passed on to page-only pagevec operations.
|
|
*/
|
|
void pagevec_remove_exceptionals(struct pagevec *pvec)
|
|
{
|
|
int i, j;
|
|
|
|
for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
|
|
struct page *page = pvec->pages[i];
|
|
if (!radix_tree_exceptional_entry(page))
|
|
pvec->pages[j++] = page;
|
|
}
|
|
pvec->nr = j;
|
|
}
|
|
|
|
/**
|
|
* pagevec_lookup - gang pagecache lookup
|
|
* @pvec: Where the resulting pages are placed
|
|
* @mapping: The address_space to search
|
|
* @start: The starting page index
|
|
* @nr_pages: The maximum number of pages
|
|
*
|
|
* pagevec_lookup() will search for and return a group of up to @nr_pages pages
|
|
* in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a
|
|
* reference against the pages in @pvec.
|
|
*
|
|
* The search returns a group of mapping-contiguous pages with ascending
|
|
* indexes. There may be holes in the indices due to not-present pages.
|
|
*
|
|
* pagevec_lookup() returns the number of pages which were found.
|
|
*/
|
|
unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
|
|
pgoff_t start, unsigned nr_pages)
|
|
{
|
|
pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
|
|
return pagevec_count(pvec);
|
|
}
|
|
EXPORT_SYMBOL(pagevec_lookup);
|
|
|
|
unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
|
|
pgoff_t *index, int tag, unsigned nr_pages)
|
|
{
|
|
pvec->nr = find_get_pages_tag(mapping, index, tag,
|
|
nr_pages, pvec->pages);
|
|
return pagevec_count(pvec);
|
|
}
|
|
EXPORT_SYMBOL(pagevec_lookup_tag);
|
|
|
|
/*
|
|
* Perform any setup for the swap system
|
|
*/
|
|
void __init swap_setup(void)
|
|
{
|
|
unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
|
|
#ifdef CONFIG_SWAP
|
|
int i;
|
|
|
|
if (bdi_init(swapper_spaces[0].backing_dev_info))
|
|
panic("Failed to init swap bdi");
|
|
for (i = 0; i < MAX_SWAPFILES; i++) {
|
|
spin_lock_init(&swapper_spaces[i].tree_lock);
|
|
INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
|
|
}
|
|
#endif
|
|
|
|
/* Use a smaller cluster for small-memory machines */
|
|
if (megs < 16)
|
|
page_cluster = 2;
|
|
else
|
|
page_cluster = 3;
|
|
/*
|
|
* Right now other parts of the system means that we
|
|
* _really_ don't want to cluster much more
|
|
*/
|
|
}
|