From: Tomasz Chmielewski <mangoo@wpkg.org>
To: Saru Addep <saru.dpm@gmail.com>
Cc: cpufreq@lists.linux.org.uk, Martin.Leisner@xerox.com
Subject: Re: Overall picture of cpufreq..
Date: Mon, 14 Jan 2008 08:08:50 +0100 [thread overview]
Message-ID: <478B0A82.6050503@wpkg.org> (raw)
In-Reply-To: <9f79f7f50801131812x6a68c202tb4c25fa2116b32e4@mail.gmail.com>
Saru Addep schrieb:
> Hi Thomas,
>
> So that means if we have an ondemand governor properly instrumented, there
> is no need to have userspace governor. In the case of ondemand governor, the
> only work that will be left to userspace would be to set the min, and max
> freq. The complete intelligence of DVFS algoritm is present inside the
> ondemand governor. Is my understanding correct.
It looks to me that ondemand governor doesn't have "the complete
intelligence".
For example, it doesn't detect CPU load coming from some kernel tasks,
like kcryptd: reads/writes from a device crypted with dm-crypt will be
very slow if one uses the ondemand governor, as CPU speed will always be
set to the lowest possible (so there is not enough power to
crypt/decrypt data).
Ironically, this is the only case when starting bzip2 will speed up your
disk access... Or, use a userspace governor.
See also http://bugzilla.kernel.org/show_bug.cgi?id=9729
--
Tomasz Chmielewski
http://wpkg.org
next prev parent reply other threads:[~2008-01-14 7:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-11 22:15 Overall picture of cpufreq Saru Addep
2008-01-11 22:50 ` Leisner, Martin
2008-01-13 22:54 ` Thomas Renninger
2008-01-14 2:12 ` Saru Addep
2008-01-14 7:08 ` Tomasz Chmielewski [this message]
2008-01-14 7:51 ` Saru Addep
2008-01-14 9:51 ` Thomas Renninger
2008-01-14 10:16 ` Tomasz Chmielewski
2008-01-14 10:32 ` Thomas Renninger
2008-01-14 10:59 ` Tomasz Chmielewski
2008-01-14 19:13 ` Saru Addep
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