[Bugme-new] [Bug 12482] New: Change cpufreq_ondemand to tread SCHED_IDLE time as idle time

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=12482

           Summary: Change cpufreq_ondemand to tread SCHED_IDLE time as idle
                    time
           Product: Power Management
           Version: 2.5
     KernelVersion: 2.6.29-rc2
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: cpufreq
        AssignedTo: cpufreq at vger.kernel.org
        ReportedBy: jimsantelmo at gmail.com


I run boinc-client, meaning I always have background jobs which are ioniced and
running at SCHED_IDLE priority. They are also niced, so cpufreq_ondemand as it
is ignores them if I set ignore_nice. The other day I was building a kernel,
which I niced, and it occurred to me that I would like to be able to make
processes niced below a certain level up the cpu speed. At first I tried that
approach, turning ignore_nice into a nice-fence value, but this got very ugly,
requiring looking at tasks and so forth, and I decided it was a bad idea. Then
I realised I could get the effect I wanted by getting sched.c to keep separate
track of SCHED_IDLE time and then treating that as nice time unconditionally,
regardless of the ignore-nice flag, which I could then turn off and have my
niced kernel builds speed up the cpu. Seems to work fine. I'll hope I can
attach the patch after I initiate this enhancement suggestion.

 I hated having to touch anything in /kernel, but there seemed to be no other
way around it, and having cpustat keep separate track of time in SCHED_IDLE
might be useful for something else.


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