linux-kernel - Re: [patch 0/5] Support for sanitization flag in low-level page allocator

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Message-ID: <20090528072702.796622b6@lxorguk.ukuu.org.uk>
Date:	Thu, 28 May 2009 07:27:02 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Rik van Riel <riel@...hat.com>,
	"Larry H." <research@...reption.com>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...l.org>, linux-mm@...ck.org,
	Ingo Molnar <mingo@...hat.com>, pageexec@...email.hu
Subject: Re: [patch 0/5] Support for sanitization flag in low-level page
 allocator

> > As for being swapped out - I do not believe that kernel stacks can 
> > ever be swapped out in Linux.
> 
> yes, i referred to that as an undesirable option - because it slows 
> down pthread_create() quite substantially.
> 
> This needs before/after pthread_create() benchmark results.

kernel stacks can end up places you don't expect on hypervisor based
systems.

In most respects the benchmarks are pretty irrelevant - wiping stuff has
a performance cost, but its the sort of thing you only want to do when
you have a security requirement that needs it. At that point the
performance is secondary.

Alan
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