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mm: use pagevec to rotate reclaimable page 

While running some memory intensive load, system response deteriorated just
after swap-out started.

The cause of this problem is that when a PG_reclaim page is moved to the tail
of the inactive LRU list in rotate_reclaimable_page(), lru_lock spin lock is
acquired every page writeback .  This deteriorates system performance and
makes interrupt hold off time longer when swap-out started.

Following patch solves this problem.  I use pagevec in rotating reclaimable
pages to mitigate LRU spin lock contention and reduce interrupt hold off time.

I did a test that allocating and touching pages in multiple processes, and
pinging to the test machine in flooding mode to measure response under memory
intensive load.

The test result is:

	-2.6.23-rc5
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 53222ms
	rtt min/avg/max/mdev = 0.074/0.652/172.228/7.176 ms, pipe 11, ipg/ewma
17.746/0.092 ms

	-2.6.23-rc5-patched
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 51924ms
	rtt min/avg/max/mdev = 0.072/0.108/3.884/0.114 ms, pipe 2, ipg/ewma
17.314/0.091 ms

Max round-trip-time was improved.

The test machine spec is that 4CPU(3.16GHz, Hyper-threading enabled)
8GB memory , 8GB swap.

I did ping test again to observe performance deterioration caused by taking
a ref.

	-2.6.23-rc6-with-modifiedpatch
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 53386ms
	rtt min/avg/max/mdev = 0.074/0.110/4.716/0.147 ms, pipe 2, ipg/ewma 17.801/0.129 ms

The result for my original patch is as follows.

	-2.6.23-rc5-with-originalpatch
	--- testmachine ping statistics ---
	3000 packets transmitted, 3000 received, 0% packet loss, time 51924ms
	rtt min/avg/max/mdev = 0.072/0.108/3.884/0.114 ms, pipe 2, ipg/ewma 17.314/0.091 ms

The influence to response was small.

[akpm@linux-foundation.org: fix uninitalised var warning]
[hugh@veritas.com: fix locking]
[randy.dunlap@oracle.com: fix function declaration]
[hugh@veritas.com: fix BUG at include/linux/mm.h:220!]
[hugh@veritas.com: kill redundancy in rotate_reclaimable_page]
[hugh@veritas.com: move_tail_pages into lru_add_drain]
Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hisashi Hifumi 2007-10-16 01:24:52 -07:00 committed by Linus Torvalds
parent 754af6f5a8
commit 902aaed0d9
1 changed files with 74 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

104
mm/swap.c
View File

@ -32,6 +32,10 @@
/* How many pages do we try to swap or page in/out together? */
int page_cluster;
static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs) = { 0, };
/*
* This path almost never happens for VM activity - pages are normally
* freed via pagevecs. But it gets used by networking.
@ -91,24 +95,48 @@ void put_pages_list(struct list_head *pages)
}
EXPORT_SYMBOL(put_pages_list);
/*
* pagevec_move_tail() must be called with IRQ disabled.
* Otherwise this may cause nasty races.
*/
static void pagevec_move_tail(struct pagevec *pvec)
{
int i;
int pgmoved = 0;
struct zone *zone = NULL;
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(&zone->lru_lock);
zone = pagezone;
spin_lock(&zone->lru_lock);
}
if (PageLRU(page) && !PageActive(page)) {
list_move_tail(&page->lru, &zone->inactive_list);
pgmoved++;
}
}
if (zone)
spin_unlock(&zone->lru_lock);
__count_vm_events(PGROTATED, pgmoved);
release_pages(pvec->pages, pvec->nr, pvec->cold);
pagevec_reinit(pvec);
}
/*
* 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. The page still has PageWriteback set, which will pin it.
*
* We don't expect many pages to come through here, so don't bother batching
* things up.
*
* To avoid placing the page at the tail of the LRU while PG_writeback is still
* set, this function will clear PG_writeback before performing the page
* motion. Do that inside the lru lock because once PG_writeback is cleared
* we may not touch the page.
* inactive list.
*
* Returns zero if it cleared PG_writeback.
*/
int rotate_reclaimable_page(struct page *page)
{
struct zone *zone;
struct pagevec *pvec;
unsigned long flags;
if (PageLocked(page))
@ -120,15 +148,16 @@ int rotate_reclaimable_page(struct page *page)
if (!PageLRU(page))
return 1;
zone = page_zone(page);
spin_lock_irqsave(&zone->lru_lock, flags);
if (PageLRU(page) && !PageActive(page)) {
list_move_tail(&page->lru, &zone->inactive_list);
__count_vm_event(PGROTATED);
}
page_cache_get(page);
local_irq_save(flags);
pvec = &__get_cpu_var(lru_rotate_pvecs);
if (!pagevec_add(pvec, page))
pagevec_move_tail(pvec);
local_irq_restore(flags);
if (!test_clear_page_writeback(page))
BUG();
spin_unlock_irqrestore(&zone->lru_lock, flags);
return 0;
}
@ -172,9 +201,6 @@ EXPORT_SYMBOL(mark_page_accessed);
* lru_cache_add: add a page to the page lists
* @page: the page to add
*/
static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
void fastcall lru_cache_add(struct page *page)
{
struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
@ -195,21 +221,37 @@ void fastcall lru_cache_add_active(struct page *page)
put_cpu_var(lru_add_active_pvecs);
}
static void __lru_add_drain(int cpu)
/*
* 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.
*/
static void drain_cpu_pagevecs(int cpu)
{
struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
struct pagevec *pvec;
/* CPU is dead, so no locking needed. */
pvec = &per_cpu(lru_add_pvecs, cpu);
if (pagevec_count(pvec))
__pagevec_lru_add(pvec);
pvec = &per_cpu(lru_add_active_pvecs, cpu);
if (pagevec_count(pvec))
__pagevec_lru_add_active(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);
}
}
void lru_add_drain(void)
{
__lru_add_drain(get_cpu());
drain_cpu_pagevecs(get_cpu());
put_cpu();
}
@ -256,6 +298,7 @@ void release_pages(struct page **pages, int nr, int cold)
int i;
struct pagevec pages_to_free;
struct zone *zone = NULL;
unsigned long uninitialized_var(flags);
pagevec_init(&pages_to_free, cold);
for (i = 0; i < nr; i++) {
@ -263,7 +306,7 @@ void release_pages(struct page **pages, int nr, int cold)
if (unlikely(PageCompound(page))) {
if (zone) {
spin_unlock_irq(&zone->lru_lock);
spin_unlock_irqrestore(&zone->lru_lock, flags);
zone = NULL;
}
put_compound_page(page);
@ -277,9 +320,10 @@ void release_pages(struct page **pages, int nr, int cold)
struct zone *pagezone = page_zone(page);
if (pagezone != zone) {
if (zone)
spin_unlock_irq(&zone->lru_lock);
spin_unlock_irqrestore(&zone->lru_lock,
flags);
zone = pagezone;
spin_lock_irq(&zone->lru_lock);
spin_lock_irqsave(&zone->lru_lock, flags);
}
VM_BUG_ON(!PageLRU(page));
__ClearPageLRU(page);
@ -288,7 +332,7 @@ void release_pages(struct page **pages, int nr, int cold)
if (!pagevec_add(&pages_to_free, page)) {
if (zone) {
spin_unlock_irq(&zone->lru_lock);
spin_unlock_irqrestore(&zone->lru_lock, flags);
zone = NULL;
}
__pagevec_free(&pages_to_free);
@ -296,7 +340,7 @@ void release_pages(struct page **pages, int nr, int cold)
}
}
if (zone)
spin_unlock_irq(&zone->lru_lock);
spin_unlock_irqrestore(&zone->lru_lock, flags);
pagevec_free(&pages_to_free);
}
@ -489,7 +533,7 @@ static int cpu_swap_callback(struct notifier_block *nfb,
if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
atomic_add(*committed, &vm_committed_space);
*committed = 0;
__lru_add_drain((long)hcpu);
drain_cpu_pagevecs((long)hcpu);
}
return NOTIFY_OK;
}