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From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Shakeel Butt <shakeelb@google.com>, Roman Gushchin <guro@fb.com>,
	Michal Hocko <mhocko@kernel.org>, Linux MM <linux-mm@kvack.org>,
	Cgroups <cgroups@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] memcg: optimize memory.numa_stat like memory.stat
Date: Thu, 23 Apr 2020 22:38:52 -0400	[thread overview]
Message-ID: <20200424023852.GA464082@cmpxchg.org> (raw)
In-Reply-To: <20200423161009.973c645420a4d17ded2a67ee@linux-foundation.org>

On Thu, Apr 23, 2020 at 04:10:09PM -0700, Andrew Morton wrote:
> From: Shakeel Butt <shakeelb@google.com>
> Subject: mm/memcg: optimize memory.numa_stat like memory.stat
> 
> Currently reading memory.numa_stat traverses the underlying memcg tree
> multiple times to accumulate the stats to present the hierarchical view of
> the memcg tree.  However the kernel already maintains the hierarchical
> view of the stats and use it in memory.stat.  Just use the same mechanism
> in memory.numa_stat as well.
> 
> I ran a simple benchmark which reads root_mem_cgroup's memory.numa_stat
> file in the presense of 10000 memcgs.  The results are:
> 
> Without the patch:
> $ time cat /dev/cgroup/memory/memory.numa_stat > /dev/null
> 
> real    0m0.700s
> user    0m0.001s
> sys     0m0.697s
> 
> With the patch:
> $ time cat /dev/cgroup/memory/memory.numa_stat > /dev/null
> 
> real    0m0.001s
> user    0m0.001s
> sys     0m0.000s
> 
> [akpm@linux-foundation.org: avoid forcing out-of-line code generation]
> Link: http://lkml.kernel.org/r/20200304022058.248270-1-shakeelb@google.com
> Signed-off-by: Shakeel Butt <shakeelb@google.com>
> Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Roman Gushchin <guro@fb.com>
> Cc: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Ouch, yes. That makes sense.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

      reply	other threads:[~2020-04-24  2:38 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-04  2:20 Shakeel Butt
2020-03-06  4:41 ` Andrew Morton
2020-03-06  4:54   ` Shakeel Butt
2020-04-23 22:59     ` Shakeel Butt
2020-04-23 23:10       ` Andrew Morton
2020-04-24  2:38         ` Johannes Weiner [this message]

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