Date: Thu, 18 Feb 2010 17:03:30 +0100
From: Andi Kleen <andi@firstfloor.org>
To: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>, Anton Blanchard <anton@samba.org>,
       tglx@linutronix.de, davem@davemloft.net, linux-kernel@vger.kernel.org,
       arjan@infradead.org, venkatesh.pallipadi@intel.com
Subject: Re: NO_HZ migration of TCP ack timers
Message-ID: <20100218160329.GG5964@basil.fritz.box>
References: <20100218052820.GD24270@kryten> <87mxz755ks.fsf@basil.nowhere.org> <20100218103301.GB26101@linux.vnet.ibm.com>
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> > > What should we do? Should we use mod_timer_pinned here? Or is this an issue
> > 
> > Sounds like something that should be controlled by the cpufreq governour's
> > idle predictor? Only migrate if predicted idle time is long enough.
> > It's essentially the same problem as deciding how deeply idle to put
> > a CPU. Heavy measures only pay off if the expected time is long enough.
> > 
> 
> cpuidle infrastructure hs statistics about the idle times for
> all the cpus. Maybe we can look to use this infrastructure to decide
> whether to migrate timers or not?

Yes sorry I reallhy meant cpuidle when I wrote cpufreq. 
That's what I suggested too.

But if the problem is lock contention on the target CPU that would
still not completely solve it, just make it less frequent depending
on the idle pattern.

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.
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