From: Peter Zijlstra <peterz@infradead.org>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
axboe@kernel.dk, rafael.j.wysocki@intel.com, mingo@kernel.org,
preeti@linux.vnet.ibm.com, Morten.Rasmussen@arm.com,
mturquette@linaro.org, tuukka.tikkanen@linaro.org,
nicolas.pitre@linaro.org, patches@linaro.org
Subject: Re: [RFD PATCH 10/10] sched: io_latency: Tracking via buckets
Date: Thu, 30 Oct 2014 15:46:34 +0100 [thread overview]
Message-ID: <20141030144634.GH23531@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <1413986273-28522-11-git-send-email-daniel.lezcano@linaro.org>
On Wed, Oct 22, 2014 at 03:57:53PM +0200, Daniel Lezcano wrote:
> The size of the bucket is the bucket interval and represent the resolution
> of the statistic model. Eg with a bucket interval of 1us, it leads us to
> do statitics on all numbers, with of course a bad prediction because the
> number of latencies is big. A big interval can give better statistics,
> but can give us a misprediction as the interval is larger.
>
> Choosing the size of the bucket interval vs the idle sleep time is the
> tradeoff to find. With a 200us bucket interval, the measurements show
> we still have good predictions, less mispredictions and cover the idle
> state target residency.
>
For the record:
The suggestion in DUS was to align the bucket sizes with the various
break even times of the actual C states.
I forgot who suggested this; it might have been Morten; but it seems to
make sense.
next prev parent reply other threads:[~2014-10-30 14:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-22 13:57 [RFD PATCH 00/10] cpuidle: Predict the next events with the IO latencies Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 01/10] sched: add io latency framework Daniel Lezcano
2014-10-28 3:19 ` Len Brown
2014-10-30 14:44 ` Peter Zijlstra
2014-10-22 13:57 ` [RFD PATCH 02/10] cpuidle: Checking the zero latency inside the governors does not make sense Daniel Lezcano
2014-10-28 3:11 ` Len Brown
2014-10-22 13:57 ` [RFD PATCH 03/10] sched: idle: cpudidle: Pass the latency req from idle.c Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 04/10] sched: idle: Compute next timer event and pass it the cpuidle framework Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 05/10] cpuidle: Remove unused headers for tick Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 06/10] sched: idle: Add io latency information for the next event Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 07/10] cpuidle: Add a simple select governor Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 08/10] cpuidle: select: hack - increase rating to have this governor as default Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 09/10] cpuidle: sysfs: Add per cpu idle state prediction statistics Daniel Lezcano
2014-10-22 13:57 ` [RFD PATCH 10/10] sched: io_latency: Tracking via buckets Daniel Lezcano
2014-10-30 14:46 ` Peter Zijlstra [this message]
2014-10-30 15:07 ` Nicolas Pitre
2014-10-30 14:38 ` [RFD PATCH 00/10] cpuidle: Predict the next events with the IO latencies Peter Zijlstra
2014-10-30 15:14 ` Nicolas Pitre
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