From: Arnd Bergmann <arnd@arndb.de>
To: Andi Kleen <ak@suse.de>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] [RFC] Optimize select/poll by putting small data sets on the stack
Date: Wed, 4 Jan 2006 00:28:40 +0000 [thread overview]
Message-ID: <200601040028.40633.arnd@arndb.de> (raw)
In-Reply-To: <200601032158.14057.ak@suse.de>
On Tuesday 03 January 2006 20:58, Andi Kleen wrote:
>
> This is a RFC for now. I would be interested in testing
> feedback. Patch is for 2.6.15.
>
> Optimize select and poll by a using stack space for small fd sets
>
> This brings back an old optimization from Linux 2.0. Using
> the stack is faster than kmalloc. On a Intel P4 system
> it speeds up a select of a single pty fd by about 13%
> (~4000 cycles -> ~3500)
Hmm, can you include the same change for compat_sys_select()?
When that was introduced, sys_select and compat_sys_select were
basically identical in their code, which makes it a lot easier
to verify that the compat_ version is correct.
Interestingly, doing a diff between sys_select and compat_sys_select
in the current kernel seems to suggest that they are both buggy
in that they miss checks for failing __put_user, but in /different/
places.
Arnd <><
next prev parent reply other threads:[~2006-01-04 0:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-03 20:58 [PATCH] [RFC] Optimize select/poll by putting small data sets on the stack Andi Kleen
2006-01-03 22:14 ` Eric Dumazet
2006-01-03 23:05 ` Andi Kleen
2006-01-03 23:07 ` Eric Dumazet
2006-01-03 23:13 ` Andi Kleen
2006-01-03 22:22 ` Jesper Juhl
2006-01-03 23:07 ` Andi Kleen
2006-01-04 0:28 ` Arnd Bergmann [this message]
2006-01-04 0:33 ` Andi Kleen
2006-01-04 0:43 ` Eric Dumazet
2006-01-04 0:48 ` Andi Kleen
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