On Tue, Nov 24, 2015 at 03:10:59AM -0800, Jacob Pan wrote: > On Tue, 24 Nov 2015 11:09:56 +0100 > Peter Zijlstra <[email protected]> wrote: > > > On Tue, Nov 24, 2015 at 09:12:40AM +0000, Javi Merino wrote: > > > On Mon, Nov 23, 2015 at 07:07:06PM +0100, Peter Zijlstra wrote: > > > > On Mon, Nov 23, 2015 at 05:56:44PM +0000, Javi Merino wrote: > > > > > I've tested this series on Juno (2xCortex-A57 4xCortex-A53). > > > > > If you idle inject for 50% of the time, when I run 6 busy loops > > > > > the scheduler sometimes keeps two of them in the same cpu while > > > > > the another cpu is completely idle. Without idle injection the > > > > > scheduler does the sensible thing: put one busy loop in each > > > > > CPU. I'm running systemd and this only happens with > > > > > CONFIG_SCHED_AUTOGROUP=y. If I unset CONFIG_SCHED_AUTOGROUP, > > > > > the tasks are spread across all cpus as usual. > > > > > > > > That's not a plus for this patch though; but a bug report against > > > > AUTOGROUP/cgroup muck, right? > > > > > > The bug only happens when you apply this series and you set the > > > system to idle inject 50% of the time. SCHED_AUTOGROUP is already > > > part of the kernel and behaves properly with the kernel as is. I > > > think that this patch should not introduce new bugs. > > > > Ah, then I misunderstood your email, agreed. > First of all, thanks for testing. > Just trying to reproduce this. So let me understand your set up. > - 8 cores in total?
- 6 cores in total > - you first set 50% idle > - then launch 6 busy loops Correct > How often you see this happen? About 1 in 10. Sometimes, even though it ends up doing the right thing, it takes some time (>500ms) to move things around. This never happens with idle injection disabled (kernel.sched_cfs_idle_inject_pct = 0). Admittedly, the situation is a lot better than with 4.3. When I first tried this series on top of v4.3-rc6, the scheduler consistently misbehaved with 50% idle injection, leaving up to 4 100% tasks on a cpu while three cpus remain completely idle Cheers, Javi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
