linux-kernel - Re: [PATCH 1/3] powernow-k6: disable cache when changing frequency

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:	Mon, 6 Jan 2014 15:17:13 -0500 (EST)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] powernow-k6: disable cache when changing frequency



On Fri, 3 Jan 2014, Viresh Kumar wrote:

> On 2 January 2014 23:08, Mikulas Patocka <mpatocka@...hat.com> wrote:
> > Flushing the cache and changing frequency takes approximatelly 500us. The
> > patch increases policy->cpuinfo.transition_latency to that value.
> 
> Its not about how fast caches get cleaned but how much time would
> be wasted to get them filled again as same data could be required again
> which is just flushed out. That would impact performance more than
> flushing caches.

I didn't see any performance degradation when I tried changing the 
frequency manually with or without the cache flush patch - the overhead of 
running cpufreq (8ms) is far worse than the frequency transition itself.

Mikulas
--
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/