From: Rik van Riel <riel@redhat.com>
To: linux-kernel@vger.kernel.org, Hugh Dickins <hughd@google.com>,
linux-mm <linux-mm@kvack.org>
Subject: Re: Repeated fork() causes SLAB to grow without bound
Date: Sat, 18 Aug 2012 00:10:14 -0400 [thread overview]
Message-ID: <502F15A6.5060902@redhat.com> (raw)
In-Reply-To: <20120818040747.GA22793@evergreen.ssec.wisc.edu>
On 08/18/2012 12:07 AM, Daniel Forrest wrote:
> I was being careful since I wasn't certain about the locking. Does
> the test need to be protected by "lock_anon_vma_root"? That's why I
> chose the overhead of the possible wasted "anon_vma_chain_alloc".
The function anon_vma_clone is being called from fork().
When running fork(), the kernel holds the mm->mmap_sem for
write, which prevents page faults by the parent process.
This means if the anon_vma in question belongs to the parent
process, no new pages will be added to it in this time.
Likewise, if the anon_vma belonged to a grandparent process,
any new pages instantiated in it will not be visible to the
parent process, or to the newly created process. This means
it is safe to skip the anon_vma.
--
All rights reversed
WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: linux-kernel@vger.kernel.org, Hugh Dickins <hughd@google.com>,
linux-mm <linux-mm@kvack.org>
Subject: Re: Repeated fork() causes SLAB to grow without bound
Date: Sat, 18 Aug 2012 00:10:14 -0400 [thread overview]
Message-ID: <502F15A6.5060902@redhat.com> (raw)
In-Reply-To: <20120818040747.GA22793@evergreen.ssec.wisc.edu>
On 08/18/2012 12:07 AM, Daniel Forrest wrote:
> I was being careful since I wasn't certain about the locking. Does
> the test need to be protected by "lock_anon_vma_root"? That's why I
> chose the overhead of the possible wasted "anon_vma_chain_alloc".
The function anon_vma_clone is being called from fork().
When running fork(), the kernel holds the mm->mmap_sem for
write, which prevents page faults by the parent process.
This means if the anon_vma in question belongs to the parent
process, no new pages will be added to it in this time.
Likewise, if the anon_vma belonged to a grandparent process,
any new pages instantiated in it will not be visible to the
parent process, or to the newly created process. This means
it is safe to skip the anon_vma.
--
All rights reversed
--
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next prev parent reply other threads:[~2012-08-18 4:10 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 [this message]
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
2014-11-19 2:48 ` Rik van Riel
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