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From: Rik van Riel <riel@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>,
	Hugh Dickins <hughd@google.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Tim Hartrick <tim@edgecast.com>, Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCH] Repeated fork() causes SLAB to grow without bound
Date: Tue, 18 Nov 2014 21:48:00 -0500	[thread overview]
Message-ID: <546C04E0.4090209@redhat.com> (raw)
In-Reply-To: <20141118121936.07b02545a0684b2cc839a10c@linux-foundation.org>

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 11/18/2014 03:19 PM, Andrew Morton wrote:
> On Mon, 17 Nov 2014 21:41:57 -0500 Rik van Riel <riel@redhat.com>
> wrote:
> 

>> That way people can understand what the code does simply by
>> looking at the changelog - no need to go find old linux-kernel
>> mailing list threads.
> 
> Yes please, there's a ton of stuff here which we should attempt to 
> capture.
> 
> https://lkml.org/lkml/2012/8/15/765 is useful.
> 
> I'm assuming that with the "foo < 5" hack, an application which
> forked 5 times then did a lot of work would still trigger the
> "catastrophic issue at page reclaim time" issue which Rik
> identified at https://lkml.org/lkml/2012/8/20/265?

It's not "forking 5 times", it is "forking >>5 generations deep".

There are a few programs that do that, but it does not appear
that they are forking servers like apache or sendmail (which
fork from the 2nd generation, and then sometimes again to exec
a helper from the 4th generation).

> There are real-world workloads which are triggering this slab
> growth problem, yes?  (Detail them in the changelog, please).

There are, but the overlap between "forks >>5 generations deep"
and "forks a bajillion child processes" appears to be zero.

- -- 
All rights reversed
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Michel Lespinasse <walken@google.com>,
	Hugh Dickins <hughd@google.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Tim Hartrick <tim@edgecast.com>, Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCH] Repeated fork() causes SLAB to grow without bound
Date: Tue, 18 Nov 2014 21:48:00 -0500	[thread overview]
Message-ID: <546C04E0.4090209@redhat.com> (raw)
In-Reply-To: <20141118121936.07b02545a0684b2cc839a10c@linux-foundation.org>

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 11/18/2014 03:19 PM, Andrew Morton wrote:
> On Mon, 17 Nov 2014 21:41:57 -0500 Rik van Riel <riel@redhat.com>
> wrote:
> 

>> That way people can understand what the code does simply by
>> looking at the changelog - no need to go find old linux-kernel
>> mailing list threads.
> 
> Yes please, there's a ton of stuff here which we should attempt to 
> capture.
> 
> https://lkml.org/lkml/2012/8/15/765 is useful.
> 
> I'm assuming that with the "foo < 5" hack, an application which
> forked 5 times then did a lot of work would still trigger the
> "catastrophic issue at page reclaim time" issue which Rik
> identified at https://lkml.org/lkml/2012/8/20/265?

It's not "forking 5 times", it is "forking >>5 generations deep".

There are a few programs that do that, but it does not appear
that they are forking servers like apache or sendmail (which
fork from the 2nd generation, and then sometimes again to exec
a helper from the 4th generation).

> There are real-world workloads which are triggering this slab
> growth problem, yes?  (Detail them in the changelog, please).

There are, but the overlap between "forks >>5 generations deep"
and "forks a bajillion child processes" appears to be zero.

- -- 
All rights reversed
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Version: GnuPG v1

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  parent reply	other threads:[~2014-11-19  2:48 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-16  2:46 Repeated fork() causes SLAB to grow without bound Daniel Forrest
2012-08-16 18:58 ` Rik van Riel
2012-08-16 18:58   ` Rik van Riel
2012-08-18  0:03   ` Daniel Forrest
2012-08-18  0:03     ` Daniel Forrest
2012-08-18  3:46     ` Rik van Riel
2012-08-18  3:46       ` Rik van Riel
2012-08-18  4:07       ` Daniel Forrest
2012-08-18  4:07         ` Daniel Forrest
2012-08-18  4:10         ` Rik van Riel
2012-08-18  4:10           ` Rik van Riel
2012-08-20  8:00       ` Hugh Dickins
2012-08-20  8:00         ` Hugh Dickins
2012-08-20  9:39         ` Michel Lespinasse
2012-08-20  9:39           ` Michel Lespinasse
2012-08-20 11:11           ` Andi Kleen
2012-08-20 11:11             ` Andi Kleen
2012-08-20 11:17           ` Rik van Riel
2012-08-20 11:17             ` Rik van Riel
2012-08-20 11:53             ` Michel Lespinasse
2012-08-20 11:53               ` Michel Lespinasse
2012-08-20 19:11               ` Michel Lespinasse
2012-08-20 19:11                 ` Michel Lespinasse
2012-08-22  3:20           ` [RFC PATCH] " Michel Lespinasse
2012-08-22  3:20             ` Michel Lespinasse
2012-08-22  3:29             ` Rik van Riel
2012-08-22  3:29               ` Rik van Riel
2013-06-03 19:50               ` Daniel Forrest
2013-06-03 19:50                 ` Daniel Forrest
2013-06-04 10:37                 ` Rik van Riel
2013-06-04 10:37                   ` Rik van Riel
2013-06-05 14:02                   ` Andrea Arcangeli
2013-06-05 14:02                     ` Andrea Arcangeli
2014-11-14 16:30                 ` [PATCH] " Daniel Forrest
2014-11-14 16:30                   ` Daniel Forrest
2014-11-18  0:02                   ` Andrew Morton
2014-11-18  0:02                     ` Andrew Morton
2014-11-18  1:41                     ` Daniel Forrest
2014-11-18  1:41                       ` Daniel Forrest
2014-11-18  2:41                       ` Rik van Riel
2014-11-18  2:41                         ` Rik van Riel
2014-11-18 20:19                         ` Andrew Morton
2014-11-18 20:19                           ` Andrew Morton
2014-11-18 22:15                           ` Konstantin Khlebnikov
2014-11-18 22:15                             ` Konstantin Khlebnikov
2014-11-18 23:02                             ` Konstantin Khlebnikov
2014-11-18 23:50                               ` Vlastimil Babka
2014-11-18 23:50                                 ` Vlastimil Babka
2014-11-19 14:36                                 ` Konstantin Khlebnikov
2014-11-19 14:36                                   ` Konstantin Khlebnikov
2014-11-19 16:09                                   ` Vlastimil Babka
2014-11-19 16:09                                     ` Vlastimil Babka
2014-11-19 16:58                                     ` Konstantin Khlebnikov
2014-11-19 16:58                                       ` Konstantin Khlebnikov
2014-11-19 23:14                                       ` Michel Lespinasse
2014-11-19 23:14                                         ` Michel Lespinasse
2014-11-20 14:42                                         ` Konstantin Khlebnikov
2014-11-20 14:42                                           ` Konstantin Khlebnikov
2014-11-20 14:50                                           ` Rik van Riel
2014-11-20 14:50                                             ` Rik van Riel
2014-11-20 15:03                                             ` Konstantin Khlebnikov
2014-11-20 15:03                                               ` Konstantin Khlebnikov
2014-11-24  7:09                                               ` Konstantin Khlebnikov
2014-11-25 10:59                                                 ` Michal Hocko
2014-11-25 10:59                                                   ` Michal Hocko
2014-11-25 12:13                                                   ` Konstantin Khlebnikov
2014-11-25 15:00                                                     ` Michal Hocko
2014-11-25 15:00                                                       ` Michal Hocko
2014-11-26 17:35                                                       ` Michal Hocko
2014-11-26 17:35                                                         ` Michal Hocko
2014-12-05 15:44                                                         ` Jerome Marchand
2014-11-20 15:27                                           ` Michel Lespinasse
2014-11-20 15:27                                             ` Michel Lespinasse
2014-11-19  2:48                           ` Rik van Riel [this message]
2014-11-19  2:48                             ` Rik van Riel

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