linux-kernel - Re: [PATCH 4/4, v2] x86: enlightenment for ticket spin locks

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Message-ID: <1277889854.1868.104.camel@laptop>
Date:	Wed, 30 Jun 2010 11:24:14 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jan Beulich <JBeulich@...ell.com>
Cc:	jeremy.fitzhardinge@...rix.com, mingo@...e.hu, tglx@...utronix.de,
	Ky Srinivasan <KSrinivasan@...ell.com>,
	linux-kernel@...r.kernel.org, hpa@...or.com
Subject: Re: [PATCH 4/4, v2] x86: enlightenment for ticket spin locks -
 improve yield behavior on Xen

On Wed, 2010-06-30 at 09:49 +0100, Jan Beulich wrote:
> >>> On 30.06.10 at 10:11, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Tue, 2010-06-29 at 15:35 +0100, Jan Beulich wrote:
> >> 
> >> The (only) additional overhead this introduces for native execution is
> >> the writing of the owning CPU in the lock acquire paths. 
> > 
> > Uhm, and growing the size of spinlock_t to 6 (or 8 bytes when aligned)
> > bytes when NR_CPUS>256.
> 
> Indeed, I should have mentioned that. Will do so in an eventual
> next version.

It would be good to also get a measure of data structure bloat caused by
this, not sure .data section size is representable there, but its
something easy to provide.

Something like: pahole -s build/vmlinux | awk '{t+=$2} END {print t}'
from before and after might also be interesting.
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