From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Mel Gorman <mgorman@suse.de>
Cc: Rafael J Wysocki <rafael.j.wysocki@intel.com>,
Nicolas Pitre <nico@linaro.org>,
Mike Galbraith <mgalbraith@suse.de>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/4] Reduce overhead of menu governor
Date: Wed, 06 Aug 2014 21:17:45 +0200 [thread overview]
Message-ID: <3495244.HqlX2f8Ijd@vostro.rjw.lan> (raw)
In-Reply-To: <1407331161-4642-1-git-send-email-mgorman@suse.de>
On Wednesday, August 06, 2014 02:19:17 PM Mel Gorman wrote:
> The menu_select function is heavy and is very noticable in profiles for
> workloads that enter/leave idle state a lot. This primarily happens
> for scheduler microbenchmarks. The biggest contibution is the standard
> deviation calculations and comparisons but the excessive calls into
> the scheduler core do not help.
>
> It would be nice to reduce the number of times nr_iowait is checked to
> once per 8 intervals but I was not sure how to measure what the general
> impact of such a change could be.
>
> Similiarly I looked at different ways the standard deviation could be
> calculated but the standard equivalent calculations potentially overflow.
> It could be done as rolling average and rolling deviation but again
> it was unclear how that could be evaluated. Tips on how the goodness/badness
> of governor changes are evalated would be nice.
>
> In the meantime, here are patches against some of the obvious stuff.
They look good, I'm going to apply them.
Rafael
prev parent reply other threads:[~2014-08-06 18:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-06 13:19 Mel Gorman
2014-08-06 13:19 ` [PATCH 1/4] cpuidle: menu: Use shifts when calculating averages where possible Mel Gorman
2014-08-06 13:19 ` [PATCH 2/4] cpuidle: menu: Use ktime_to_us instead of reinventing the wheel Mel Gorman
2014-08-06 14:17 ` Daniel Lezcano
2014-08-06 13:19 ` [PATCH 3/4] cpuidle: menu: Call nr_iowait_cpu less times Mel Gorman
2014-08-06 13:19 ` [PATCH 4/4] cpuidle: menu: Lookup CPU runqueues less Mel Gorman
2014-08-06 19:17 ` Rafael J. Wysocki [this message]
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