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| author | Johannes Weiner <hannes@cmpxchg.org> | 2016-07-28 15:45:10 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-07-28 16:07:41 -0700 |
| commit | 55779ec759ccc3c12b917b3712a7716e1140c652 (patch) | |
| tree | d119d51e0c82b2535f0a6519799f5387b94192f6 /mm/workingset.c | |
| parent | 400bc7fd4fa7d33c96d836e6b65eeed246f1959a (diff) | |
| download | lwn-55779ec759ccc3c12b917b3712a7716e1140c652.tar.gz lwn-55779ec759ccc3c12b917b3712a7716e1140c652.zip | |
mm: fix vm-scalability regression in cgroup-aware workingset code
Commit 23047a96d7cf ("mm: workingset: per-cgroup cache thrash
detection") added a page->mem_cgroup lookup to the cache eviction,
refault, and activation paths, as well as locking to the activation
path, and the vm-scalability tests showed a regression of -23%.
While the test in question is an artificial worst-case scenario that
doesn't occur in real workloads - reading two sparse files in parallel
at full CPU speed just to hammer the LRU paths - there is still some
optimizations that can be done in those paths.
Inline the lookup functions to eliminate calls. Also, page->mem_cgroup
doesn't need to be stabilized when counting an activation; we merely
need to hold the RCU lock to prevent the memcg from being freed.
This cuts down on overhead quite a bit:
23047a96d7cfcfca 063f6715e77a7be5770d6081fe
---------------- --------------------------
%stddev %change %stddev
\ | \
21621405 +- 0% +11.3% 24069657 +- 2% vm-scalability.throughput
[linux@roeck-us.net: drop unnecessary include file]
[hannes@cmpxchg.org: add WARN_ON_ONCE()s]
Link: http://lkml.kernel.org/r/20160707194024.GA26580@cmpxchg.org
Link: http://lkml.kernel.org/r/20160624175101.GA3024@cmpxchg.org
Reported-by: Ye Xiaolong <xiaolong.ye@intel.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/workingset.c')
| -rw-r--r-- | mm/workingset.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/mm/workingset.c b/mm/workingset.c index 577277546d98..d7cc4bbd7e1b 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -305,9 +305,10 @@ bool workingset_refault(void *shadow) */ void workingset_activation(struct page *page) { + struct mem_cgroup *memcg; struct lruvec *lruvec; - lock_page_memcg(page); + rcu_read_lock(); /* * Filter non-memcg pages here, e.g. unmap can call * mark_page_accessed() on VDSO pages. @@ -315,12 +316,13 @@ void workingset_activation(struct page *page) * XXX: See workingset_refault() - this should return * root_mem_cgroup even for !CONFIG_MEMCG. */ - if (!mem_cgroup_disabled() && !page_memcg(page)) + memcg = page_memcg_rcu(page); + if (!mem_cgroup_disabled() && !memcg) goto out; - lruvec = mem_cgroup_zone_lruvec(page_zone(page), page_memcg(page)); + lruvec = mem_cgroup_zone_lruvec(page_zone(page), memcg); atomic_long_inc(&lruvec->inactive_age); out: - unlock_page_memcg(page); + rcu_read_unlock(); } /* |