[LARTC] cpufreq affects rate in, at least, htb

[LARTC] cpufreq affects rate in, at least, htb

[DervishD]

    Hi all :)

    I've tested this and having a cpufreq that slows down the CPU
affects the rate of HTB. My ondemand cpufreq governor scales down the
CPU frequency about 40% and this is more or less the slowdown the rate
suffers, 40%.

    Any known way of dealing with this without having to disable
cpufreq?

    Thanks in advance :)

    Raúl Núñez de Arenas Coronado

-- 
Linux Registered User 88736 | http://www.dervishd.net
It's my PC and I'll cry if I want to... RAmen!
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Re: [LARTC] cpufreq affects rate in, at least, htb

[Andreas Mueller]

Hi, DervishD

DervishD wrote:
>     Hi all :)
> 
>     I've tested this and having a cpufreq that slows down the CPU
> affects the rate of HTB. My ondemand cpufreq governor scales down the
> CPU frequency about 40% and this is more or less the slowdown the rate
> suffers, 40%.
> 
>     Any known way of dealing with this without having to disable
> cpufreq?
> 
>     Thanks in advance :)
> 
>     Raúl Núñez de Arenas Coronado
> 

What kernel-version do you use?

In 2.6.22 another timer is used for psched.
Maybe NO_HZ could interfere on this issue too.

Bye,
 Andreas.
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Re: [LARTC] cpufreq affects rate in, at least, htb

[DervishD]

    Hi Andreas :)

 * Andreas Mueller <andreas@stapelspeicher.org> dixit:
> DervishD wrote:
> >     Hi all :)
> > 
> >     I've tested this and having a cpufreq that slows down the CPU
> > affects the rate of HTB. My ondemand cpufreq governor scales down the
> > CPU frequency about 40% and this is more or less the slowdown the rate
> > suffers, 40%.
> > 
> >     Any known way of dealing with this without having to disable
> > cpufreq?
> > 
> 
> What kernel-version do you use?

    Sorry, I forgot to include that documentation... I'm using
2.6.20.14, and I was waiting until 2.6.22 stable branch reached at least
10 (I'm tired of regressions with all 2.6.x kernels, so I try to avoid
updating if possible).
 
> In 2.6.22 another timer is used for psched.

    I'll give it a try, then, but not before 2.6.22.10 at least.

> Maybe NO_HZ could interfere on this issue too.

    Currently I have CONFIG_HZ_1000=y and CONFIG_HZ\x1000, and no
tickless idle since that feature was introduced in a later kernel.
Probably the problem is the shared timer and I will have to use 2.6.22
kernel to have it if I dare upgrading ;))

    Thanks for the information, Andreas :)

    Raúl Núñez de Arenas Coronado

-- 
Linux Registered User 88736 | http://www.dervishd.net
It's my PC and I'll cry if I want to... RAmen!
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Re: [LARTC] cpufreq affects rate in, at least, htb

[Adam James]

On Tue, 28 Aug 2007 09:47:38 +0200
DervishD <lartc@dervishd.net> wrote:

>     I've tested this and having a cpufreq that slows down the CPU
> affects the rate of HTB. My ondemand cpufreq governor scales down the
> CPU frequency about 40% and this is more or less the slowdown the rate
> suffers, 40%.

This is expected behaviour when CONFIG_NET_SCH_CLK_CPU is defined:

	Say Y here if you want to use the CPU's cycle counter as clock
	source.

	This is a cheap and high resolution clock source, but on some
	architectures it is not synchronized on all processors
	and doesn't handle cpu clock frequency changes.

>     Any known way of dealing with this without having to disable
> cpufreq?

Yes, specify a different clock source in your kernel configuration.

--atj


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Re: [LARTC] cpufreq affects rate in, at least, htb

[DervishD]

    Hi Adam :)

 * Adam James <ad@heliosphan.co.uk> dixit:
> On Tue, 28 Aug 2007 09:47:38 +0200
> DervishD <lartc@dervishd.net> wrote:
> 
> >     I've tested this and having a cpufreq that slows down the CPU
> > affects the rate of HTB. My ondemand cpufreq governor scales down the
> > CPU frequency about 40% and this is more or less the slowdown the rate
> > suffers, 40%.
> 
> This is expected behaviour when CONFIG_NET_SCH_CLK_CPU is defined:

    Sh*t! I thought I changed that when I turned on cpufreq and set it
to jiffies, but I've seen my /proc/kconfig.gz and it's not true, I have
CONFIG_NET_SCH_CLK_CPU :((((

    Sorry for the noise, I'm embarrassed... And thanks a lot for your
help.

    Raúl Núñez de Arenas Coronado

-- 
Linux Registered User 88736 | http://www.dervishd.net
It's my PC and I'll cry if I want to... RAmen!
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