Mailinglist Archive: opensuse-factory (710 mails)

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Re: [opensuse-factory] Systemd by default
On Wed, 2011-06-01 at 11:34 +0200, Stefan Seyfried wrote:
Am Wed, 1 Jun 2011 05:25:13 +0800
schrieb Greg KH <gregkh@xxxxxxx>:

On Tue, May 31, 2011 at 09:57:12AM +0200, Stefan Seyfried wrote:
I never expected to see such pathological workload in the wild, but it
exists ;)

Have you reported this bug to the kernel developers?

This is no bug. There are pathological workloads.

Pseudo code:

for(;;) {
receive(&data); /* blocks until data is received */
compute_with_high_cpuload_but finish_quickly(&data);

If the computation is finished in << 100ms, the cpufreq will not be
switched up. Sleep time between data blocks is large (> 100ms)

Now imagine three such processes on three servers, handing data around in

Switching to "performance" governor did increase the end-user performance
by 30%.

I've seen this with ping-pong loads to localhost. On-demand doesn't (or
at least didn't) always kick the cpu up a gear when we're using two
cores with shared cache. The thing seems to get confused by the idle
time.. doesn't realize that high frequency idle/busy transitions mean
high speed communication.


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