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Commit 2d6f75d6 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by james toy
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shrink_all_zone() was introduced by commit d6277db4 (swsusp: rework 

memory shrinker) for hibernate performance improvement.  and
sc.swap_cluster_max was introduced by commit a06fe4d307 (Speed freeing
memory for suspend).

commit a06fe4d307 said

   Without the patch:
   Freed  14600 pages in  1749 jiffies = 32.61 MB/s (Anomolous!)
   Freed  88563 pages in 14719 jiffies = 23.50 MB/s
   Freed 205734 pages in 32389 jiffies = 24.81 MB/s

   With the patch:
   Freed  68252 pages in   496 jiffies = 537.52 MB/s
   Freed 116464 pages in   569 jiffies = 798.54 MB/s
   Freed 209699 pages in   705 jiffies = 1161.89 MB/s

At that time, their patch was pretty worth.  However, Modern Hardware
trend and recent VM improvement broke its worth.  From several reason, I
think we should remove shrink_all_zones() at all.

detail:

1) Old days, shrink_zone()'s slowness was mainly caused by stupid io-throttle
  at no i/o congestion.
  but current shrink_zone() is sane, not slow.

2) shrink_all_zone() try to shrink all pages at a time. but it doesn't works
  fine on numa system.
  example)
    System has 4GB memory and each node have 2GB. and hibernate need 1GB.

    optimal)
       steal 500MB from each node.
    shrink_all_zones)
       steal 1GB from node-0.

  Oh, Cache balancing logic was broken. ;)
  Unfortunately, Desktop system moved ahead NUMA at nowadays.
  (Side note, if hibernate require 2GB, shrink_all_zones() never success
   on above machine)

3) if the node has several I/O flighting pages, shrink_all_zones() makes
  pretty bad result.

  schenario) hibernate need 1GB

  1) shrink_all_zones() try to reclaim 1GB from Node-0
  2) but it only reclaimed 990MB
  3) stupidly, shrink_all_zones() try to reclaim 1GB from Node-1
  4) it reclaimed 990MB

  Oh, well. it reclaimed twice much than required.
  In the other hand, current shrink_zone() has sane baling out logic.
  then, it doesn't make overkill reclaim. then, we lost shrink_zones()'s risk.

4) SplitLRU VM always keep active/inactive ratio very carefully. inactive list only
  shrinking break its assumption. it makes unnecessary OOM risk. it obviously suboptimal.

Now, shrink_all_memory() is only the wrapper function of do_try_to_free_pages().
it bring good reviewability and debuggability, and solve above problems.

side note: Reclaim logic unificication makes two good side effect.
 - Fix recursive reclaim bug on shrink_all_memory().
   it did forgot to use PF_MEMALLOC. it mean the system be able to stuck into deadlock.
 - Now, shrink_all_memory() got lockdep awareness. it bring good debuggability.
Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent d906707f
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Inline Side-by-side
Showing with 26 additions and 127 deletions
mm/vmscan.c
View file @ 2d6f75d6
......@@ -58,6 +58,8 @@ struct scan_control {
/* How many pages shrink_list() should reclaim */
unsigned long nr_to_reclaim;
unsigned long hibernation_mode;
/* This context's GFP mask */
gfp_t gfp_mask;
......@@ -1800,7 +1802,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
}
/* Take a nap, wait for some writeback to complete */
if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
if (!sc->hibernation_mode && sc->nr_scanned &&
priority < DEF_PRIORITY - 2)
congestion_wait(BLK_RW_BOTH, HZ/10);
}
/* top priority shrink_zones still had more to do? don't OOM, then */
......@@ -2334,148 +2337,44 @@ unsigned long zone_reclaimable_pages(struct zone *zone)
#ifdef CONFIG_HIBERNATION
/*
* Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
* from LRU lists system-wide, for given pass and priority.
*
* For pass > 3 we also try to shrink the LRU lists that contain a few pages
*/
static void shrink_all_zones(unsigned long nr_pages, int prio,
int pass, struct scan_control *sc)
{
struct zone *zone;
unsigned long nr_reclaimed = 0;
struct zone_reclaim_stat *reclaim_stat;
for_each_populated_zone(zone) {
enum lru_list l;
if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
continue;
for_each_evictable_lru(l) {
enum zone_stat_item ls = NR_LRU_BASE + l;
unsigned long lru_pages = zone_page_state(zone, ls);
/* For pass = 0, we don't shrink the active list */
if (pass == 0 && (l == LRU_ACTIVE_ANON ||
l == LRU_ACTIVE_FILE))
continue;
reclaim_stat = get_reclaim_stat(zone, sc);
reclaim_stat->nr_saved_scan[l] +=
(lru_pages >> prio) + 1;
if (reclaim_stat->nr_saved_scan[l]
>= nr_pages || pass > 3) {
unsigned long nr_to_scan;
reclaim_stat->nr_saved_scan[l] = 0;
nr_to_scan = min(nr_pages, lru_pages);
nr_reclaimed += shrink_list(l, nr_to_scan, zone,
sc, prio);
if (nr_reclaimed >= nr_pages) {
sc->nr_reclaimed += nr_reclaimed;
return;
}
}
}
}
sc->nr_reclaimed += nr_reclaimed;
}
/*
* Try to free `nr_pages' of memory, system-wide, and return the number of
* Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
* freed pages.
*
* Rather than trying to age LRUs the aim is to preserve the overall
* LRU order by reclaiming preferentially
* inactive > active > active referenced > active mapped
*/
unsigned long shrink_all_memory(unsigned long nr_pages)
unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
{
unsigned long lru_pages, nr_slab;
int pass;
struct reclaim_state reclaim_state;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.may_unmap = 0,
.gfp_mask = GFP_HIGHUSER_MOVABLE,
.may_swap = 1,
.may_unmap = 1,
.may_writepage = 1,
.swap_cluster_max = SWAP_CLUSTER_MAX,
.nr_to_reclaim = nr_to_reclaim,
.hibernation_mode = 1,
.swappiness = vm_swappiness,
.order = 0,
.isolate_pages = isolate_pages_global,
.nr_reclaimed = 0,
};
struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
struct task_struct *p = current;
unsigned long nr_reclaimed;
current->reclaim_state = &reclaim_state;
lru_pages = global_reclaimable_pages();
nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
/* If slab caches are huge, it's better to hit them first */
while (nr_slab >= lru_pages) {
reclaim_state.reclaimed_slab = 0;
shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
if (!reclaim_state.reclaimed_slab)
break;
sc.nr_reclaimed += reclaim_state.reclaimed_slab;
if (sc.nr_reclaimed >= nr_pages)
goto out;
nr_slab -= reclaim_state.reclaimed_slab;
}
/*
* We try to shrink LRUs in 5 passes:
* 0 = Reclaim from inactive_list only
* 1 = Reclaim from active list but don't reclaim mapped
* 2 = 2nd pass of type 1
* 3 = Reclaim mapped (normal reclaim)
* 4 = 2nd pass of type 3
*/
for (pass = 0; pass < 5; pass++) {
int prio;
/* Force reclaiming mapped pages in the passes #3 and #4 */
if (pass > 2)
sc.may_unmap = 1;
for (prio = DEF_PRIORITY; prio >= 0; prio--) {
unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
sc.nr_scanned = 0;
sc.swap_cluster_max = nr_to_scan;
shrink_all_zones(nr_to_scan, prio, pass, &sc);
if (sc.nr_reclaimed >= nr_pages)
goto out;
reclaim_state.reclaimed_slab = 0;
shrink_slab(sc.nr_scanned, sc.gfp_mask,
global_reclaimable_pages());
sc.nr_reclaimed += reclaim_state.reclaimed_slab;
if (sc.nr_reclaimed >= nr_pages)
goto out;
if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
congestion_wait(BLK_RW_ASYNC, HZ / 10);
}
}
/*
* If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
* something in slab caches
*/
if (!sc.nr_reclaimed) {
do {
reclaim_state.reclaimed_slab = 0;
shrink_slab(nr_pages, sc.gfp_mask,
global_reclaimable_pages());
sc.nr_reclaimed += reclaim_state.reclaimed_slab;
} while (sc.nr_reclaimed < nr_pages &&
reclaim_state.reclaimed_slab > 0);
}
p->flags |= PF_MEMALLOC;
lockdep_set_current_reclaim_state(sc.gfp_mask);
reclaim_state.reclaimed_slab = 0;
p->reclaim_state = &reclaim_state;
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
out:
current->reclaim_state = NULL;
p->reclaim_state = NULL;
lockdep_clear_current_reclaim_state();
p->flags &= ~PF_MEMALLOC;
return sc.nr_reclaimed;
return nr_reclaimed;
}
#endif /* CONFIG_HIBERNATION */
......
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