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 <[EMAIL PROTECTED]>
---
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 {
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Reply via email to