netdev - Re: [tbench regression fixes]: digging out smelly deadmen.

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Message-Id: <200810251313.21120.rjw@sisk.pl>
Date:	Sat, 25 Oct 2008 13:13:20 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	David Miller <davem@...emloft.net>
Cc:	mingo@...e.hu, s0mbre@...rvice.net.ru, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, efault@....de
Subject: Re: [tbench regression fixes]: digging out smelly deadmen.

On Saturday, 25 of October 2008, David Miller wrote:
> From: "Rafael J. Wysocki" <rjw@...k.pl>
> Date: Sat, 25 Oct 2008 00:25:34 +0200
> 
> > On Friday, 10 of October 2008, Ingo Molnar wrote:
> > > 
> > > * Evgeniy Polyakov <s0mbre@...rvice.net.ru> wrote:
> > > 
> > > > On Fri, Oct 10, 2008 at 01:42:45PM +0200, Ingo Molnar (mingo@...e.hu) wrote:
> > > > > > vanilla 27: 347.222
> > > > > > no TSO/GSO: 357.331
> > > > > > no hrticks: 382.983
> > > > > > no balance: 389.802
> > > > > 
> > > > > okay. The target is 470 MB/sec, right? (Assuming the workload is sane 
> > > > > and 'fixing' it does not mean we have to schedule worse.)
> > > > 
> > > > Well, that's where I started/stopped, so maybe we will even move
> > > > further? :)
> > > 
> > > that's the right attitude ;)
> > 
> > Can anyone please tell me if there was any conclusion of this thread?
> 
> I made some more analysis in private with Ingo and Peter Z. and found
> that the tbench decreases correlate pretty much directly with the
> ongoing increasing cpu cost of wake_up() and friends in the fair
> scheduler.
> 
> The largest increase in computational cost of wakeups came in 2.6.27
> when the hrtimer bits got added, it more than tripled the cost of a wakeup.
> In 2.6.28-rc1 the hrtimer feature has been disabled, but I think that
> should be backports into the 2.6.27-stable branch.

Thanks a lot for the info.

Could you please give me a pointer to the commit disabling the hrtimer feature?

Rafael
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