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From: Johannes Weiner <hannes@cmpxchg.org>
To: Roman Gushchin <guro@fb.com>
Cc: "Michal Koutný" <mkoutny@suse.com>,
	"Richard Palethorpe" <rpalethorpe@suse.com>,
	ltp@lists.linux.it, "Andrew Morton" <akpm@linux-foundation.org>,
	"Shakeel Butt" <shakeelb@google.com>,
	"Christoph Lameter" <cl@linux.com>,
	"Michal Hocko" <mhocko@kernel.org>, "Tejun Heo" <tj@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	"Michal Hocko" <mhocko@suse.com>
Subject: Re: [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root
Date: Tue, 20 Oct 2020 14:18:22 -0400	[thread overview]
Message-ID: <20201020181822.GA397401@cmpxchg.org> (raw)
In-Reply-To: <20201020170717.GA153102@carbon.DHCP.thefacebook.com>

On Tue, Oct 20, 2020 at 10:07:17AM -0700, Roman Gushchin wrote:
> If we want these counter to function properly, then we should go into the opposite
> direction and remove the special handling of the root memory cgroup in many places.

I suspect this is also by far the most robust solution from a code and
maintenance POV.

I don't recall the page counter at the root level having been a
concern in recent years, even though it's widely used in production
environments. It's lockless and cache compact. It's also per-cpu
batched, which means it isn't actually part of the memcg hotpath.

WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes@cmpxchg.org>
To: ltp@lists.linux.it
Subject: [LTP] [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root
Date: Tue, 20 Oct 2020 14:18:22 -0400	[thread overview]
Message-ID: <20201020181822.GA397401@cmpxchg.org> (raw)
In-Reply-To: <20201020170717.GA153102@carbon.DHCP.thefacebook.com>

On Tue, Oct 20, 2020 at 10:07:17AM -0700, Roman Gushchin wrote:
> If we want these counter to function properly, then we should go into the opposite
> direction and remove the special handling of the root memory cgroup in many places.

I suspect this is also by far the most robust solution from a code and
maintenance POV.

I don't recall the page counter at the root level having been a
concern in recent years, even though it's widely used in production
environments. It's lockless and cache compact. It's also per-cpu
batched, which means it isn't actually part of the memcg hotpath.

  reply	other threads:[~2020-10-20 18:20 UTC|newest]

Thread overview: 96+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-14 19:07 [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root Richard Palethorpe
2020-10-14 19:07 ` [LTP] " Richard Palethorpe
2020-10-14 20:08 ` Roman Gushchin
2020-10-14 20:08   ` [LTP] " Roman Gushchin
2020-10-16  5:40   ` Richard Palethorpe
2020-10-16  5:40     ` [LTP] " Richard Palethorpe
2020-10-16  6:32     ` [LTP] [PATCH v2] " Richard Palethorpe
2020-10-16  9:47 ` [RFC PATCH] " Michal Koutný
2020-10-16  9:47   ` [LTP] " Michal =?unknown-8bit?q?Koutn=C3=BD?=
2020-10-16 10:41   ` Richard Palethorpe
2020-10-16 10:41     ` [LTP] " Richard Palethorpe
2020-10-16 15:05     ` Richard Palethorpe
2020-10-16 15:05       ` [LTP] " Richard Palethorpe
2020-10-16 17:26       ` Michal Koutný
2020-10-16 17:26         ` [LTP] " Michal =?unknown-8bit?q?Koutn=C3=BD?=
2020-10-16 14:53   ` Johannes Weiner
2020-10-16 14:53     ` [LTP] " Johannes Weiner
2020-10-16 17:02     ` Roman Gushchin
2020-10-16 17:02       ` [LTP] " Roman Gushchin
2020-10-16 17:15     ` Michal Koutný
2020-10-16 17:15       ` [LTP] " Michal =?unknown-8bit?q?Koutn=C3=BD?=
2020-10-19  8:45       ` Richard Palethorpe
2020-10-19  8:45         ` [LTP] " Richard Palethorpe
2020-10-19  9:58         ` [PATCH v3] " Richard Palethorpe
2020-10-19  9:58           ` [LTP] " Richard Palethorpe
2020-10-19 16:58           ` Shakeel Butt
2020-10-19 16:58             ` [LTP] " Shakeel Butt
2020-10-19 16:58             ` Shakeel Butt
2020-10-20  5:52             ` Richard Palethorpe
2020-10-20  5:52               ` [LTP] " Richard Palethorpe
2020-10-20 13:49               ` Richard Palethorpe
2020-10-20 13:49                 ` [LTP] " Richard Palethorpe
2020-10-20 16:56                 ` Shakeel Butt
2020-10-20 16:56                   ` [LTP] " Shakeel Butt
2020-10-20 16:56                   ` Shakeel Butt
2020-10-21 20:32                   ` Roman Gushchin
2020-10-21 20:32                     ` [LTP] " Roman Gushchin
2020-10-20 17:24               ` Michal Koutný
2020-10-20 17:24                 ` [LTP] " Michal =?unknown-8bit?q?Koutn=C3=BD?=
2020-10-22  7:04                 ` Richard Palethorpe
2020-10-22  7:04                   ` [LTP] " Richard Palethorpe
2020-10-22 12:28                   ` [PATCH v4] " Richard Palethorpe
2020-10-22 12:28                     ` [LTP] " Richard Palethorpe
2020-10-22 16:37                     ` Shakeel Butt
2020-10-22 16:37                       ` [LTP] " Shakeel Butt
2020-10-22 16:37                       ` Shakeel Butt
2020-10-22 17:25                       ` Roman Gushchin
2020-10-22 17:25                         ` [LTP] " Roman Gushchin
2020-10-22 23:59                         ` Shakeel Butt
2020-10-22 23:59                           ` [LTP] " Shakeel Butt
2020-10-22 23:59                           ` Shakeel Butt
2020-10-23  0:40                           ` Roman Gushchin
2020-10-23  0:40                             ` [LTP] " Roman Gushchin
2020-10-23 15:44                             ` Johannes Weiner
2020-10-23 15:44                               ` [LTP] " Johannes Weiner
2020-10-23 16:41                             ` Shakeel Butt
2020-10-23 16:41                               ` [LTP] " Shakeel Butt
2020-10-23 16:41                               ` Shakeel Butt
2020-10-26  7:32                             ` Richard Palethorpe
2020-10-26  7:32                               ` [LTP] " Richard Palethorpe
2020-10-26 23:14                               ` Roman Gushchin
2020-10-26 23:14                                 ` [LTP] " Roman Gushchin
2020-10-19 22:28       ` [RFC PATCH] " Roman Gushchin
2020-10-19 22:28         ` [LTP] " Roman Gushchin
2020-10-20  6:04         ` Richard Palethorpe
2020-10-20  6:04           ` [LTP] " Richard Palethorpe
2020-10-20 12:02           ` Richard Palethorpe
2020-10-20 12:02             ` [LTP] " Richard Palethorpe
2020-10-20 14:48         ` Richard Palethorpe
2020-10-20 14:48           ` [LTP] " Richard Palethorpe
2020-10-20 16:27         ` Michal Koutný
2020-10-20 16:27           ` [LTP] " Michal =?unknown-8bit?q?Koutn=C3=BD?=
2020-10-20 17:07           ` Roman Gushchin
2020-10-20 17:07             ` [LTP] " Roman Gushchin
2020-10-20 18:18             ` Johannes Weiner [this message]
2020-10-20 18:18               ` Johannes Weiner
2020-10-21 19:33               ` Roman Gushchin
2020-10-21 19:33                 ` [LTP] " Roman Gushchin
2020-10-23 16:30                 ` Johannes Weiner
2020-10-23 16:30                   ` [LTP] " Johannes Weiner
2020-11-10  1:27                   ` Roman Gushchin
2020-11-10  1:27                     ` [LTP] " Roman Gushchin
2020-11-10 15:11                     ` Shakeel Butt
2020-11-10 15:11                       ` [LTP] " Shakeel Butt
2020-11-10 19:13                       ` Roman Gushchin
2020-11-10 19:13                         ` [LTP] " Roman Gushchin
2020-11-20 17:46                       ` Michal Koutný
2020-11-20 17:46                         ` [LTP] " Michal =?unknown-8bit?q?Koutn=C3=BD?=
2020-11-03 13:22                 ` Michal Hocko
2020-11-03 13:22                   ` [LTP] " Michal Hocko
2020-11-03 21:30                   ` Roman Gushchin
2020-11-03 21:30                     ` [LTP] " Roman Gushchin
2020-10-20 16:55         ` Shakeel Butt
2020-10-20 16:55           ` [LTP] " Shakeel Butt
2020-10-20 17:17           ` Roman Gushchin
2020-10-20 17:17             ` [LTP] " Roman Gushchin

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