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From: Roman Gushchin <guro@fb.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH 0/4] mm: memcontrol: memory.stat cost & correctness
Date: Fri, 12 Apr 2019 22:04:02 +0000	[thread overview]
Message-ID: <20190412220357.GA18999@tower.DHCP.thefacebook.com> (raw)
In-Reply-To: <20190412151507.2769-1-hannes@cmpxchg.org>

On Fri, Apr 12, 2019 at 11:15:03AM -0400, Johannes Weiner wrote:
> The cgroup memory.stat file holds recursive statistics for the entire
> subtree. The current implementation does this tree walk on-demand
> whenever the file is read. This is giving us problems in production.
> 
> 1. The cost of aggregating the statistics on-demand is high. A lot of
> system service cgroups are mostly idle and their stats don't change
> between reads, yet we always have to check them. There are also always
> some lazily-dying cgroups sitting around that are pinned by a handful
> of remaining page cache; the same applies to them.
> 
> In an application that periodically monitors memory.stat in our fleet,
> we have seen the aggregation consume up to 5% CPU time.
> 
> 2. When cgroups die and disappear from the cgroup tree, so do their
> accumulated vm events. The result is that the event counters at
> higher-level cgroups can go backwards and confuse some of our
> automation, let alone people looking at the graphs over time.
> 
> To address both issues, this patch series changes the stat
> implementation to spill counts upwards when the counters change.
> 
> The upward spilling is batched using the existing per-cpu cache. In a
> sparse file stress test with 5 level cgroup nesting, the additional
> cost of the flushing was negligible (a little under 1% of CPU at 100%
> CPU utilization, compared to the 5% of reading memory.stat during
> regular operation).
> 
>  include/linux/memcontrol.h |  96 +++++++-------
>  mm/memcontrol.c            | 290 +++++++++++++++++++++++++++----------------
>  mm/vmscan.c                |   4 +-
>  mm/workingset.c            |   7 +-
>  4 files changed, 234 insertions(+), 163 deletions(-)
> 
> 

For the series:
Reviewed-by: Roman Gushchin <guro@fb.com>

Thanks!

      parent reply	other threads:[~2019-04-12 22:04 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-12 15:15 [PATCH 0/4] mm: memcontrol: memory.stat cost & correctness Johannes Weiner
2019-04-12 15:15 ` [PATCH 1/4] mm: memcontrol: make cgroup stats and events query API explicitly local Johannes Weiner
2019-04-12 15:15 ` [PATCH 2/4] mm: memcontrol: move stat/event counting functions out-of-line Johannes Weiner
2019-04-12 15:15 ` [PATCH 3/4] mm: memcontrol: fix recursive statistics correctness & scalabilty Johannes Weiner
2019-04-12 19:55   ` Shakeel Butt
2019-04-12 20:10     ` Johannes Weiner
2019-04-12 20:38       ` Shakeel Butt
2019-04-12 20:15     ` Roman Gushchin
2019-04-12 20:50       ` Shakeel Butt
2019-04-12 15:15 ` [PATCH 4/4] mm: memcontrol: fix NUMA round-robin reclaim at intermediate level Johannes Weiner
2019-04-12 20:07 ` [PATCH 0/4] mm: memcontrol: memory.stat cost & correctness Shakeel Butt
2019-04-12 22:04 ` Roman Gushchin [this message]

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