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SubjectRe: Fwd: Nice processes prevent frequency increases - possible scheduler regression (known good in 2.6.35)
On Sat, Nov 3, 2012 at 12:48 PM, Mike Galbraith <> wrote:
> On Sat, 2012-11-03 at 04:33 -0700, Mike Galbraith wrote:
>> On Fri, 2012-11-02 at 21:09 +0100, Michal Zatloukal wrote:
>> > On the new kernel, the nice processes are never starved - even when
>> > starting a tab-laden chromium session, the processes for BOINC keep
>> > about 20% CPU each (that is normalized to all CPUs, ie 40% nice load
>> > on each core). The problem is, the governor now seems to consider the
>> > non-nice task unable to saturate the CPU, and the cores' frequencies
>> > are hovering between 1.0 and 1.8 GHz. The scheduler keeps scheduling
>> > the nice tasks, and the non-nice tasks are progressing much slower,
>> > caused by the lower CPU speed as well as less processing time
>> > allocated to them. HD video stutters often, and Chromium takes at
>> > least 2-3 times longer to fully load.
>> Your nice 19 tasks receiving 'too much' CPU when there are other
>> runnable tasks around sounds like you have SCHED_AUTOGROUP enabled.
> (forgot to mention: if that's the case, you can add noautogroup to your
> kernel command line to turn it off if distro turned it on in .config)

Thanks, Ubuntu's kernel is indeed configured with that option enabled,
and passing "noautogroup" at grub restores the previous behaviour. I'm
back to happy days again :) BTW, isn't this the "magic 200-line patch"
I was reading about ~2 years ago?


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