Messages in this thread Patch in this message | | | Subject | [PATCH] Cgroup: Fix memory accounting scalability in shrink_page_list | From | Tim Chen <> | Date | Thu, 19 Jul 2012 16:34:26 -0700 |
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Hi,
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> diff --git a/mm/vmscan.c b/mm/vmscan.c index 33dc256..aac5672 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -779,6 +779,7 @@ 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; @@ -1026,6 +1027,7 @@ keep_lumpy: 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;
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