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From: Roman Gushchin <guro@fb.com>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: <hannes@cmpxchg.org>, <mhocko@kernel.org>,
	<vdavydov.dev@gmail.com>, <akpm@linux-foundation.org>,
	<shakeelb@google.com>, <vbabka@suse.cz>, <willy@infradead.org>,
	<songmuchun@bytedance.com>, <shy828301@gmail.com>,
	<surenb@google.com>, <linux-kernel@vger.kernel.org>,
	<cgroups@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [PATCH 4/4] mm/memcg: refine mem_cgroup_threshold_ary->current_threshold calculation
Date: Tue, 11 Jan 2022 10:23:41 -0800	[thread overview]
Message-ID: <Yd3LLalWzPy17PmR@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20220111010302.8864-4-richard.weiyang@gmail.com>

On Tue, Jan 11, 2022 at 01:03:02AM +0000, Wei Yang wrote:
> mem_cgroup_threshold_ary->current_threshold points to the last entry
> who's threshold is less or equal to usage.
> 
> Instead of iterating entries to get the correct index, we can leverage
> primary->current_threshold to get it. If the threshold added is less or
> equal to usage, current_threshold should increase by one. Otherwise, it
> doesn't change.

How big is usually an array of thresholds? If it's not huge, likely
any savings won't be really noticeable (it's not a hot path and there
is an rc_synchronize() below).

So I agree with Michal that a better justification is really needed.

Thanks!

WARNING: multiple messages have this Message-ID (diff)
From: Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>
To: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org,
	mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
	shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	vbabka-AlSwsSmVLrQ@public.gmane.org,
	willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org,
	songmuchun-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org,
	shy828301-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	surenb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org
Subject: Re: [PATCH 4/4] mm/memcg: refine mem_cgroup_threshold_ary->current_threshold calculation
Date: Tue, 11 Jan 2022 10:23:41 -0800	[thread overview]
Message-ID: <Yd3LLalWzPy17PmR@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20220111010302.8864-4-richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

On Tue, Jan 11, 2022 at 01:03:02AM +0000, Wei Yang wrote:
> mem_cgroup_threshold_ary->current_threshold points to the last entry
> who's threshold is less or equal to usage.
> 
> Instead of iterating entries to get the correct index, we can leverage
> primary->current_threshold to get it. If the threshold added is less or
> equal to usage, current_threshold should increase by one. Otherwise, it
> doesn't change.

How big is usually an array of thresholds? If it's not huge, likely
any savings won't be really noticeable (it's not a hot path and there
is an rc_synchronize() below).

So I agree with Michal that a better justification is really needed.

Thanks!

  parent reply	other threads:[~2022-01-11 18:24 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-11  1:02 [PATCH 1/4] mm/memcg: use NUMA_NO_NODE to indicate allocation from unspecified node Wei Yang
2022-01-11  1:02 ` Wei Yang
2022-01-11  1:03 ` [PATCH 2/4] mm/memcg: mem_cgroup_per_node is already set to 0 on allocation Wei Yang
2022-01-11  2:25   ` Muchun Song
2022-01-11  2:25     ` Muchun Song
2022-01-11  8:41   ` Michal Hocko
2022-01-11 18:06   ` Roman Gushchin
2022-01-11 18:06     ` Roman Gushchin
2022-01-14 11:08   ` Mike Rapoport
2022-01-16 19:24   ` Shakeel Butt
2022-01-16 19:24     ` Shakeel Butt
2022-01-11  1:03 ` [PATCH 3/4] mm/memcg: retrieve parent memcg from css.parent Wei Yang
2022-01-11  1:03   ` Wei Yang
2022-01-11  3:12   ` Muchun Song
2022-01-11  3:12     ` Muchun Song
2022-01-11  8:43   ` Michal Hocko
2022-01-11 18:09   ` Roman Gushchin
2022-01-11 18:09     ` Roman Gushchin
2022-01-12  0:24     ` Wei Yang
2022-01-12  0:24       ` Wei Yang
2022-01-16 19:54   ` Shakeel Butt
2022-01-16 19:54     ` Shakeel Butt
2022-01-11  1:03 ` [PATCH 4/4] mm/memcg: refine mem_cgroup_threshold_ary->current_threshold calculation Wei Yang
2022-01-11  1:03   ` Wei Yang
2022-01-11  8:44   ` Michal Hocko
2022-01-11 18:23   ` Roman Gushchin [this message]
2022-01-11 18:23     ` Roman Gushchin
2022-01-12  0:25     ` Wei Yang
2022-01-12  0:25       ` Wei Yang
2022-01-11  2:23 ` [PATCH 1/4] mm/memcg: use NUMA_NO_NODE to indicate allocation from unspecified node Muchun Song
2022-01-11  2:23   ` Muchun Song
2022-01-11  8:40 ` Michal Hocko
2022-01-11  8:40   ` Michal Hocko
2022-01-12  0:46   ` Wei Yang
2022-01-12  0:46     ` Wei Yang
2022-01-12  8:56     ` Michal Hocko
2022-01-12  8:56       ` Michal Hocko
2022-01-14  0:29       ` Wei Yang
2022-01-14  0:29         ` Wei Yang
2022-01-14  8:51         ` Michal Hocko
2022-01-14  8:51           ` Michal Hocko
2022-01-15 22:10           ` Wei Yang
2022-01-15 22:10             ` Wei Yang
2022-01-16 19:23       ` Shakeel Butt
2022-01-16 19:23         ` Shakeel Butt
2022-01-11 18:05 ` Roman Gushchin
2022-01-11 18:05   ` Roman Gushchin
2022-01-14 11:07 ` Mike Rapoport
2022-01-14 11:07   ` Mike Rapoport
2022-01-31  1:47 ` Wei Yang
2022-01-31  1:47   ` Wei Yang
2022-01-31 22:36   ` Andrew Morton
2022-01-31 22:36     ` Andrew Morton
2022-02-01  0:42     ` Wei Yang
2022-02-01  0:42       ` Wei Yang

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