linux-kernel - Re: select(0, ..) is valid ?

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Message-ID: <20070516153703.GA26912@kryten>
Date:	Wed, 16 May 2007 10:37:03 -0500
From:	Anton Blanchard <anton@...ba.org>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Christoph Lameter <clameter@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Badari Pulavarty <pbadari@...ibm.com>, netdev@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>, sfr@...b.auug.org.au,
	ak@...e.de
Subject: Re: select(0, ..) is valid ?


Hi Hugh,

> It's interesting that compat_core_sys_select() shows this kmalloc(0)
> failure but core_sys_select() does not.  That's because core_sys_select()
> avoids kmalloc by using a buffer on the stack for small allocations (and
> 0 sure is small).  Shouldn't compat_core_sys_select() do just the same?
> Or is SLUB going to be so efficient that doing so is a waste of time?

Nice catch, the original optimisation from Andi is:

http://git.kernel.org/git-new/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=70674f95c0a2ea694d5c39f4e514f538a09be36f

And I think it makes sense for the compat code to do it too.

Anton
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