linux-kernel - Re: changing timeslice in linux

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Message-ID: <87mx1phzf1.fsf@sejong.aot.lge.com>
Date:	Tue, 21 Aug 2012 09:16:50 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Xin Tong <xerox.time.tech@...il.com>
Cc:	Mike Galbraith <efault@....de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: changing timeslice in linux

On Mon, 20 Aug 2012 07:51:52 -0700, Xin Tong wrote:
> On Sun, Aug 19, 2012 at 10:54 PM, Mike Galbraith <efault@....de> wrote:
>> On Sun, 2012-08-19 at 11:58 -0700, Xin Tong wrote:
>>> I have 2 questions about linux 2.6 x86_64 scheduler.
>>>
>>> 1. is the default scheduling algorithm SCHED_NORMAL in linux ?
>>
>> Yes.
> Is there any document describing what the sched_normal is ? it is more
> difficult than SCHED_RR to infer its meaning just based on its name ?
>>
>>> 2. how do i change the time slice in linux source code ?
>>
>> You shouldn't need to.  You can tune "slice" by adjusting
>> sched_latency_ns and sched_min_granularity_ns, but note that "slice" is
>> not a fixed quantum.  Also note that CFS preemption decisions are based
>> upon instantaneous state.  A task may have received a full (variable)
>> "slice" of CPU time, but preemption will be triggered only if a more
>> deserving task is available, so a "slice" is not the "max uninterrupted
>> CPU time" that you may expect it to be.. but it is somewhat similar.
>>
>> -Mike
>>
> This can be done without recompiling and reinstalling the kernel ?
> maybe one simply needs to write to a device file under /dev ?

You can find those files under /proc/sys/kernel/.

Thanks,
Namhyung
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