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Date: Tue, 24 Aug 2010 10:14:07 +0200 From: Ingo Molnar <mingo@...e.hu> To: Peter Zijlstra <peterz@...radead.org>, Frédéric Weisbecker <fweisbec@...il.com> Cc: Venkatesh Pallipadi <venki@...gle.com>, Martin Schwidefsky <schwidefsky@...ibm.com>, "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Balbir Singh <balbir@...ux.vnet.ibm.com>, Paul Menage <menage@...gle.com>, linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>, Heiko Carstens <heiko.carstens@...ibm.com>, Paul Mackerras <paulus@...ba.org>, Tony Luck <tony.luck@...el.com> Subject: Re: [PATCH 0/4] Finer granularity and task/cgroup irq time accounting * Peter Zijlstra <peterz@...radead.org> wrote: > On Thu, 2010-07-22 at 19:12 -0700, Venkatesh Pallipadi wrote: > > > > > > Well, the task and cgroup information is there but what does it really > > > tell me? As long as the irq & softirq time can be caused by any other > > > process I don't see the value of this incorrect data point. > > > > > > > Data point will be correct. How it gets used is a different qn. This > > interface will be useful for Alert/Paranoid/Annoyed user/admin who > > sees that the job exec_time is high but it is not doing any useful > > work. > > I'm very sympathetic with Martin's POV. irq/softirq times per task > don't really make sense. In the case you provide above the solution > would be to subtract these times from the task execution time, not > break it out. In that case he would see his task not do much, and end > up with the same action list. Right, andthis connects to something Frederic sent a few RFC patches for some time ago: finegrained irq/softirq perf stat support. If we do something in this area we need a facility that enables both types of statistics gathering. Frederic's model is based on exclusion - so you could do a perf stat run that excluded softirq and hardirq execution from a workload's runtime. It's nifty, as it allows the reduction of measurement noise. (IRQ and softirq execution can be regarded as random noise added (or not added) to execution times) Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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