diff options
| author | Johannes Weiner <hannes@cmpxchg.org> | 2014-10-09 15:28:56 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-10-09 22:25:59 -0400 |
| commit | b70a2a21dc9d4ad455931b53131a0cb4fc01fafe (patch) | |
| tree | 95ad6c804009a5867ac991cc1edf414e163b40b4 /include | |
| parent | 3fbe724424fb104aaca9973389b4a9df428c3e2a (diff) | |
mm: memcontrol: fix transparent huge page allocations under pressure
In a memcg with even just moderate cache pressure, success rates for
transparent huge page allocations drop to zero, wasting a lot of effort
that the allocator puts into assembling these pages.
The reason for this is that the memcg reclaim code was never designed for
higher-order charges. It reclaims in small batches until there is room
for at least one page. Huge page charges only succeed when these batches
add up over a series of huge faults, which is unlikely under any
significant load involving order-0 allocations in the group.
Remove that loop on the memcg side in favor of passing the actual reclaim
goal to direct reclaim, which is already set up and optimized to meet
higher-order goals efficiently.
This brings memcg's THP policy in line with the system policy: if the
allocator painstakingly assembles a hugepage, memcg will at least make an
honest effort to charge it. As a result, transparent hugepage allocation
rates amid cache activity are drastically improved:
vanilla patched
pgalloc 4717530.80 ( +0.00%) 4451376.40 ( -5.64%)
pgfault 491370.60 ( +0.00%) 225477.40 ( -54.11%)
pgmajfault 2.00 ( +0.00%) 1.80 ( -6.67%)
thp_fault_alloc 0.00 ( +0.00%) 531.60 (+100.00%)
thp_fault_fallback 749.00 ( +0.00%) 217.40 ( -70.88%)
[ Note: this may in turn increase memory consumption from internal
fragmentation, which is an inherent risk of transparent hugepages.
Some setups may have to adjust the memcg limits accordingly to
accomodate this - or, if the machine is already packed to capacity,
disable the transparent huge page feature. ]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Dave Hansen <dave@sr71.net>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/swap.h | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h index ea4f926e6b9b..37a585beef5c 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -327,8 +327,10 @@ extern void lru_cache_add_active_or_unevictable(struct page *page, extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order, gfp_t gfp_mask, nodemask_t *mask); extern int __isolate_lru_page(struct page *page, isolate_mode_t mode); -extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem, - gfp_t gfp_mask, bool noswap); +extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, + unsigned long nr_pages, + gfp_t gfp_mask, + bool may_swap); extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, gfp_t gfp_mask, bool noswap, struct zone *zone, |