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Date: Thu, 27 Sep 2007 20:51:14 +0100 (BST)
From: Hugh Dickins <hugh@...itas.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>,
linux-kernel@...r.kernel.org
Subject: [PATCH mm 3/3] move_tail_pages into lru_add_drain
a.k.a. mm-use-pagevec-to-rotate-reclaimable-page-cleanup-2.patch
Opinions may differ, but I'm uneasy with leaving pages to be rotated on
their pagevecs for too long: although they're still visible via the LRU,
their page counts are raised, which excludes them from some operations.
Memory hotplug and page migration clearly want to be draining them:
but rather than add move_tail_pages calls in various places, won't we
be safer just to drain them whenever we drain the lru_add pagevecs?
So merge move_tail_pages into __lru_add_drain, which lets us remove
cpu_movetail_callback. Rename __lru_add_drain to drain_cpu_pagevecs,
and correct the misleading "CPU is dead" comment found there.
Signed-off-by: Hugh Dickins <hugh@...itas.com>
---
You may disagree with this one, or your unease with these rotation
patches may have grown to the point that you want to back them all out:
I've no strong feeling on it - it was a good idea to try to batch them,
but has turned out to be more complicated than was foreseen.
include/linux/swap.h | 1
mm/swap.c | 65 +++++++++++++++--------------------------
mm/vmscan.c | 1
3 files changed, 25 insertions(+), 42 deletions(-)
--- 2.6.23-rc8-mm2/include/linux/swap.h 2007-09-27 11:28:37.000000000 +0100
+++ linux/include/linux/swap.h 2007-09-27 17:51:49.000000000 +0100
@@ -181,7 +181,6 @@ extern void FASTCALL(mark_page_accessed(
extern void lru_add_drain(void);
extern int lru_add_drain_all(void);
extern int rotate_reclaimable_page(struct page *page);
-extern void move_tail_pages(void);
extern void swap_setup(void);
/* linux/mm/vmscan.c */
--- 2.6.23-rc8-mm2/mm/swap.c 2007-09-27 17:51:33.000000000 +0100
+++ linux/mm/swap.c 2007-09-27 17:51:49.000000000 +0100
@@ -34,6 +34,10 @@
/* 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.
@@ -125,20 +129,6 @@ static void pagevec_move_tail(struct pag
pagevec_reinit(pvec);
}
-static DEFINE_PER_CPU(struct pagevec, rotate_pvecs) = { 0, };
-
-void move_tail_pages(void)
-{
- unsigned long flags;
- struct pagevec *pvec;
-
- local_irq_save(flags);
- pvec = &__get_cpu_var(rotate_pvecs);
- if (pagevec_count(pvec))
- pagevec_move_tail(pvec);
- local_irq_restore(flags);
-}
-
/*
* 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
@@ -214,9 +204,6 @@ 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);
@@ -237,21 +224,37 @@ void fastcall lru_cache_add_active(struc
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();
}
@@ -533,25 +536,8 @@ static int cpu_swap_callback(struct noti
if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
atomic_add(*committed, &vm_committed_space);
*committed = 0;
- __lru_add_drain((long)hcpu);
- }
- return NOTIFY_OK;
-}
-
-static int cpu_movetail_callback(struct notifier_block *nfb,
- unsigned long action, void *hcpu)
-{
- unsigned long flags;
- struct pagevec *pvec;
-
- if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
- local_irq_save(flags);
- pvec = &per_cpu(rotate_pvecs, (long)hcpu);
- if (pagevec_count(pvec))
- pagevec_move_tail(pvec);
- local_irq_restore(flags);
+ drain_cpu_pagevecs((long)hcpu);
}
-
return NOTIFY_OK;
}
#endif /* CONFIG_HOTPLUG_CPU */
@@ -579,6 +565,5 @@ void __init swap_setup(void)
*/
#ifdef CONFIG_HOTPLUG_CPU
hotcpu_notifier(cpu_swap_callback, 0);
- hotcpu_notifier(cpu_movetail_callback, 0);
#endif
}
--- 2.6.23-rc8-mm2/mm/vmscan.c 2007-09-27 11:28:39.000000000 +0100
+++ linux/mm/vmscan.c 2007-09-27 17:51:49.000000000 +0100
@@ -824,7 +824,6 @@ static unsigned long shrink_inactive_lis
pagevec_init(&pvec, 1);
- move_tail_pages();
lru_add_drain();
spin_lock_irq(&zone->lru_lock);
do {
-
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