Messages in this thread | | | Date | Mon, 4 Jul 2016 22:40:21 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: Subject: PROBLEM: CPU accounting/scheduling regression in v4.6 CPU scheduling patchset? |
| |
On Sun, 3 Jul 2016, Vladimir Panteleev wrote: > Since updating my PC to Linux 4.6, I noticed the following problems: > > 1. CPU-bound tasks which use all CPU cores have a severe impact on > responsiveness. For example, the following bash command (which > simply starts one busyloop per core) is enough to make the machine > almost completely unresponsive: > > for N in $(seq $(nproc)) ; do while true ; do ; done & ; done > > 2. Nearly all tasks in the process listing are shown with 0% CPU > usage, even when they're CPU-bound. The only exceptions are the > kernel migration and kthreadd tasks, and occasionally the init > process. > > I have bisected the problem to commit > 1cf4f629d9d246519a1e76c021806f2a51ddba4d ("cpu/hotplug: Move online > calls to hotplugged cpu"), which is part of Thomas Gleixner's CPU > hotplug refactoring patchset [1]. It introduces both problems > described above.
I doubt that, but that commit has been a bisect victim before ...
> My system is a GIGABYTE X79S-UP5-WIFI motherboard (F5f BIOS) with an > i7-4960X CPU, running Arch Linux. I've reproduced with both the > distro's kernel config [2], as well as a minimal config for my > system. I can reproduce the problems on the latest rc at the moment, > v4.7-rc5. > > Comparing dmesg output before and after 1cf4f629, I see no notable > differences. > > I noticed an existing thread "S3 resume regression" [3] referencing > this commit, however it describes a different problem. I also found a > Bugzilla issue for the zero CPU usage problem [4], however it has no > replies.
That one says: * After an hour or less (I have no idea), the top/ps start working * I do have exactly the same problem with the LTS branch 4.4.14 * With 4.5.4 I cannot reproduce the problem just after booting
I tried to reproduce the issue on a couple of machines, but no luck.
No idea at the moment, but Cc'ed scheduler folks.
Thanks,
tglx
| |