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authorTim Chen <tim.c.chen@linux.intel.com>2012-07-31 16:46:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-31 18:42:49 -0700
commit69980e31754ef23307d51372e61bf7c2584f8a4b (patch)
treef36caa9cfcd5d5e118e53e6f6fdb48b1efc57e1c
parentc1c9518331969f97ea403bac66f0fd4a85d204d5 (diff)
downloadlinux-69980e31754ef23307d51372e61bf7c2584f8a4b.tar.gz
memcg: gix memory accounting scalability in shrink_page_list
I noticed in a multi-process parallel files reading benchmark I ran on a 8 socket machine, throughput slowed down by a factor of 8 when I ran the benchmark within a cgroup container. I traced the problem to the following code path (see below) when we are trying to reclaim memory from file cache. The res_counter_uncharge function is called on every page that's reclaimed and created heavy lock contention. The patch below allows the reclaimed pages to be uncharged from the resource counter in batch and recovered the regression. Tim 40.67% usemem [kernel.kallsyms] [k] _raw_spin_lock | --- _raw_spin_lock | |--92.61%-- res_counter_uncharge | | | |--100.00%-- __mem_cgroup_uncharge_common | | | | | |--100.00%-- mem_cgroup_uncharge_cache_page | | | __remove_mapping | | | shrink_page_list | | | shrink_inactive_list | | | shrink_mem_cgroup_zone | | | shrink_zone | | | do_try_to_free_pages | | | try_to_free_pages | | | __alloc_pages_nodemask | | | alloc_pages_current Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/vmscan.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index e37e6872509..8d01243d956 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -687,6 +687,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
cond_resched();
+ mem_cgroup_uncharge_start();
while (!list_empty(page_list)) {
enum page_references references;
struct address_space *mapping;
@@ -953,6 +954,7 @@ keep:
list_splice(&ret_pages, page_list);
count_vm_events(PGACTIVATE, pgactivate);
+ mem_cgroup_uncharge_end();
*ret_nr_dirty += nr_dirty;
*ret_nr_writeback += nr_writeback;
return nr_reclaimed;