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From: Michal Hocko <mhocko@suse.com>
To: David Hildenbrand <david@redhat.com>
Cc: Nico Pache <npache@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	akpm@linux-foundation.org, shakeelb@google.com,
	ktkhai@virtuozzo.com, shy828301@gmail.com, guro@fb.com,
	vbabka@suse.cz, vdavydov.dev@gmail.com, raquini@redhat.com
Subject: Re: [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker_info on offlined nodes
Date: Mon, 6 Dec 2021 15:15:01 +0100	[thread overview]
Message-ID: <Ya4a5bHjhF+57raT@dhcp22.suse.cz> (raw)
In-Reply-To: <05157de4-e5df-11fc-fc46-8a9f79d0ddb4@redhat.com>

On Mon 06-12-21 14:47:13, David Hildenbrand wrote:
> On 06.12.21 14:06, Michal Hocko wrote:
[...]
> > This is certainly possible. But it a) adds a branch to the hotpath and
> > b) it doesn't solve any other potential dereference of garbage node.
> 
> I don't think a) is  a problem but it's easy to measure.

Let me just clarify on this one. This single particular branch will be
indeed hard to match to any performance changes. On a single call of the
allocator it is nothing. But it is a condition that will be executed by
each caller while it won't ever trigger in most systems and workloads.

In other words it will cause a lot of wasted cpu cycles long term. A
more expensive one time initialization is worth in order to have
allocator fast path lighter IMHO.
-- 
Michal Hocko
SUSE Labs

  parent reply	other threads:[~2021-12-06 14:15 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-06  3:33 [RFC PATCH 0/2] mm: Dont allocate pages on a offline node Nico Pache
2021-12-06  3:33 ` [RFC PATCH 1/2] include/linux/gfp.h: Do not allocate pages on a offlined node Nico Pache
2021-12-06  3:37   ` Matthew Wilcox
2021-12-06  8:29   ` David Hildenbrand
2021-12-06  9:22   ` Michal Hocko
2021-12-07 21:24     ` Nico Pache
2021-12-06  3:33 ` [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker_info on offlined nodes Nico Pache
2021-12-06  8:32   ` David Hildenbrand
2021-12-06  9:22   ` Michal Hocko
2021-12-06  9:24     ` Michal Hocko
2021-12-06 10:45     ` David Hildenbrand
2021-12-06 10:54       ` Michal Hocko
2021-12-06 11:00         ` David Hildenbrand
2021-12-06 11:22           ` Michal Hocko
2021-12-06 12:43             ` David Hildenbrand
2021-12-06 13:06               ` Michal Hocko
2021-12-06 13:47                 ` David Hildenbrand
2021-12-06 14:06                   ` Michal Hocko
2021-12-06 14:08                     ` David Hildenbrand
2021-12-06 14:21                       ` Michal Hocko
2021-12-06 14:30                         ` Vlastimil Babka
2021-12-06 14:53                           ` Michal Hocko
2021-12-06 18:26                             ` Yang Shi
2021-12-07 10:15                               ` Michal Hocko
2021-12-06 14:15                   ` Michal Hocko [this message]
2021-12-06 13:19       ` Kirill Tkhai
2021-12-06 13:24         ` Michal Hocko
2021-12-08 19:00           ` Nico Pache
2021-12-06 18:42         ` Yang Shi
2021-12-06 19:01           ` David Hildenbrand
2021-12-06 21:28             ` Yang Shi
2021-12-07 10:15               ` David Hildenbrand
2021-12-07 10:55             ` Michal Hocko
2021-12-07 21:45         ` Nico Pache
2021-12-07 21:40       ` Nico Pache
2021-12-07 21:34     ` Nico Pache
2021-12-06 18:45   ` Yang Shi

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