linux-kernel - Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28

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Date:	Tue, 16 Sep 2008 14:28:25 +0200
From:	Mike Galbraith <efault@....de>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: [Bug #11308] tbench regression on each kernel release from
	2.6.22 -&gt; 2.6.28

On Mon, 2008-09-15 at 12:44 +0200, Mike Galbraith wrote:
> On Sun, 2008-09-14 at 21:51 +0200, Mike Galbraith wrote:
> > On Sun, 2008-09-14 at 09:18 -0500, Christoph Lameter wrote:
> > > Mike Galbraith wrote:
> > > > Numbers from my Q6600 Aldi supermarket box (hm, your box is from different shelf)
> > > >   
> > > My box is an 8p with recent quad core processors. 8G, 32bit Linux.
> > 
> > Don't hold your breath, but after putting my network config of a very
> > severe diet, I'm starting to see something resembling sensible results.
> 
> Turns off all netfilter options except tables, etc.
> 
> Since 2.6.22.19-cfs-v24.1 and 2.6.23.17-cfs-v24.1 schedulers are
> identical, and these are essentially identical with 2.6.24.7, what I
> read from numbers below is that cfs in 2.6.23 was somewhat less than
> wonderful for either netperf or tbench,  Something happened somewhere
> other than the scheduler at 23->24 which cost us some performance, and
> another something happened at 26->27.  I'll likely go looking again..
> and likely regret it again ;-)

Bisecting 26->27 yet again turned up a repeatable downturn in netperf
throughput.  There is no difference at this point with tbench. 

Bisect says first bad commit is 847106f, a security merge.  Post
bisection sanity checkouts say...

v2.6.26-21-g2069f45
16384  87380  1        1       60.00    98435.13
16384  87380  1        1       60.01    99259.90
16384  87380  1        1       60.01    99325.61
16384  87380  1        1       60.00    99039.84

v2.6.26-343-g847106f
16384  87380  1        1       60.00    94764.59
16384  87380  1        1       60.00    94909.89
16384  87380  1        1       60.00    94858.63
16384  87380  1        1       60.00    94801.12

...every time.  I knew I'd regret doing this.

	-Mike

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