linux-kernel - Re: Repeated fork() causes SLAB to grow without bound

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Message-ID: <50321CD3.5050501@redhat.com>
Date:	Mon, 20 Aug 2012 07:17:39 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Michel Lespinasse <walken@...gle.com>
CC:	Hugh Dickins <hughd@...gle.com>,
	Daniel Forrest <dan.forrest@...c.wisc.edu>,
	Andrea Arcangeli <aarcange@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: Repeated fork() causes SLAB to grow without bound

On 08/20/2012 05:39 AM, Michel Lespinasse wrote:

> I would still prefer if we could just remove the anon_vma_chain stuff, though.

If only we could.

That simply replaces a medium issue at fork time, with the
potential for a catastrophic issue at page reclaim time,
in any workload with heavily forking server software.

Without the anon_vma_chains, we end up scanning every single
one of the child processes (and the parent) for every COWed
page, which can be a real issue when the VM runs into 1000
such pages, for 1000 child processes.

Unfortunately, we have seen this happen...

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