Messages in this thread | | | Date | Wed, 20 Oct 2010 04:56:52 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC/RFT PATCH] sched: automated per tty task groups |
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* Mike Galbraith <efault@gmx.de> wrote:
> > On Tue, 2010-10-19 at 08:28 -0700, Linus Torvalds wrote: > > > > > > If people compare with a non-CGROUP_SCHED > > > kernel, will a desktop-optimized kernel suddenly have horrible pipe > > > latency due to much higher scheduling cost? Right now that whole > > > feature is hidden by EXPERIMENTAL, I don't know how much it hurts, and > > > I never timed it when I tried it out long ago.. > > Q/D test of kernels w/wo, with same .config using pipe-test (pure sched) gives on > my box ~590khz with tty_sched active, 620khz without cgroups acitve in same > kernel/config without patch. last time I measured stripped down config (not long > ago, but not yesterday either) gave max ctx rate ~690khz on this box. > > (note: very Q, very D numbers, no variance testing, ballpark)
That's 5% overhead in context switches. Definitely not in the 'horrible' category.
This would be a rather tempting item for 2.6.37 ... especially as it really mainly reuses existing group scheduling functionality, in a clever way.
Mind doing more of the tty->desktop renames/generalizations as Linus suggested, and resend the patch?
I'd also suggest to move it out of EXPERIMENTAL - we dont really do that for core kernel features as most distros enable CONFIG_EXPERIMENTAL so it's a rather meaningless distinction. Since the feature is default-n, people will get the old scheduler by default but can also choose this desktop-centric scheduling mode.
I'd even argue to make it default-y, because this patch clearly cures a form of kbuild cancer.
Thanks,
Ingo
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