linux-kernel - Re: [RFD PATCH 10/10] sched: io

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 30 Oct 2014 15:46:34 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	axboe@...nel.dk, rafael.j.wysocki@...el.com, mingo@...nel.org,
	preeti@...ux.vnet.ibm.com, Morten.Rasmussen@....com,
	mturquette@...aro.org, tuukka.tikkanen@...aro.org,
	nicolas.pitre@...aro.org, patches@...aro.org
Subject: Re: [RFD PATCH 10/10] sched: io_latency: Tracking via buckets

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.
--
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/