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Groups > linux.kernel > #1530401
| From | "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: RFC: documentation of the autogroup feature [v2] |
| Date | 2016-11-25 17:20 +0100 |
| Message-ID | <sHroe-2Rp-17@gated-at.bofh.it> (permalink) |
| References | (5 earlier) <sGJnb-7Id-17@gated-at.bofh.it> <sHa41-8qT-7@gated-at.bofh.it> <sHoJH-15u-7@gated-at.bofh.it> <sHqBQ-2hw-27@gated-at.bofh.it> <sHr4R-2rt-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 11/25/2016 04:51 PM, Mike Galbraith wrote: > On Fri, 2016-11-25 at 16:04 +0100, Michael Kerrisk (man-pages) wrote: > >>>> ┌─────────────────────────────────────────────────────┐ >>>> │FIXME │ >>>> ├─────────────────────────────────────────────────────┤ >>>> │How do the nice value of a process and the nice │ >>>> │value of an autogroup interact? Which has priority? │ >>>> │ │ >>>> │It *appears* that the autogroup nice value is used │ >>>> │for CPU distribution between task groups, and that │ >>>> │the process nice value has no effect there. (I.e., │ >>>> │suppose two autogroups each contain a CPU-bound │ >>>> │process, with one process having nice==0 and the │ >>>> │other having nice==19. It appears that they each │ >>>> │get 50% of the CPU.) It appears that the process │ >>>> │nice value has effect only with respect to schedul‐ │ >>>> │ing relative to other processes in the *same* auto‐ │ >>>> │group. Is this correct? │ >>>> └─────────────────────────────────────────────────────┘ >>> >>> Yup, entity nice level affects distribution among peer entities. >> >> Huh! I only just learned about this via my experiments while >> investigating autogroups. >> >> How long have things been like this? Always? (I don't think >> so.) Since the arrival of CFS? Since the arrival of >> autogrouping? (I'm guessing not.) Since some other point? >> (When?) > > Always. Before CFS there just were no non-peers :) Well that's one way of looking at it. So, the change that I'm talking about came in 2.6.32 with CFS then? >> It seems to me that this renders the traditional process >> nice pretty much useless. (I bet I'm not the only one who'd >> be surprised by the current behavior.) > > Yup, group scheduling is not a single edged sword, those don't exist. > Box wide nice loss is not the only thing that can bite you, fairness, > whether group or task oriented cuts both ways. Understood. But again I'll say, I bet a lot of old-time users (and maybe many newer) would be surprised by the fact that nice(1) / setpriority(2) have effectively been rendered no-ops in many use cases. At the very least, it'd have been nice if someone had sent a man pages patch or at least a note... Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
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RFC: documentation of the autogroup feature "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-22 17:20 +0100
[patch] sched/autogroup: Fix 64bit kernel nice adjustment Mike Galbraith <efault@gmx.de> - 2016-11-23 11:40 +0100
Re: [patch] sched/autogroup: Fix 64bit kernel nice adjustment "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-23 14:50 +0100
Re: [patch] sched/autogroup: Fix 64bit kernel nice adjustment Mike Galbraith <efault@gmx.de> - 2016-11-23 15:20 +0100
Re: [patch] sched/autogroup: Fix 64bit kernel nice adjustment "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-23 15:30 +0100
Re: [patch] sched/autogroup: Fix 64bit kernel nice adjustment Mike Galbraith <efault@gmx.de> - 2016-11-23 17:00 +0100
[tip:sched/urgent] sched/autogroup: Fix 64-bit kernel nice level adjustment tip-bot for Mike Galbraith <tipbot@zytor.com> - 2016-11-24 07:30 +0100
Re: RFC: documentation of the autogroup feature Mike Galbraith <efault@gmx.de> - 2016-11-23 12:50 +0100
Re: RFC: documentation of the autogroup feature "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-23 15:00 +0100
Re: RFC: documentation of the autogroup feature Mike Galbraith <efault@gmx.de> - 2016-11-23 16:40 +0100
Re: RFC: documentation of the autogroup feature "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-23 17:10 +0100
Re: RFC: documentation of the autogroup feature Mike Galbraith <efault@gmx.de> - 2016-11-23 18:20 +0100
Re: RFC: documentation of the autogroup feature "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-23 23:50 +0100
Re: RFC: documentation of the autogroup feature "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-23 17:10 +0100
Re: RFC: documentation of the autogroup feature Mike Galbraith <efault@gmx.de> - 2016-11-23 18:20 +0100
RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-24 22:50 +0100
Re: RFC: documentation of the autogroup feature [v2] Afzal Mohammed <afzal.mohd.ma@gmail.com> - 2016-11-25 14:00 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-25 14:10 +0100
Re: RFC: documentation of the autogroup feature [v2] Mike Galbraith <efault@gmx.de> - 2016-11-25 14:30 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-25 16:30 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-25 16:50 +0100
Re: RFC: documentation of the autogroup feature [v2] Mike Galbraith <efault@gmx.de> - 2016-11-25 17:00 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-25 17:20 +0100
Re: RFC: documentation of the autogroup feature [v2] Peter Zijlstra <peterz@infradead.org> - 2016-11-25 17:20 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-25 17:40 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-25 22:00 +0100
Re: RFC: documentation of the autogroup feature [v2] Peter Zijlstra <peterz@infradead.org> - 2016-11-25 22:50 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-29 08:50 +0100
Re: RFC: documentation of the autogroup feature [v2] Peter Zijlstra <peterz@infradead.org> - 2016-11-29 12:50 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-29 14:50 +0100
Re: RFC: documentation of the autogroup feature [v2] Peter Zijlstra <peterz@infradead.org> - 2016-11-25 17:10 +0100
Re: RFC: documentation of the autogroup feature [v2] Peter Zijlstra <peterz@infradead.org> - 2016-11-25 17:20 +0100
Re: RFC: documentation of the autogroup feature [v2] "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-25 17:40 +0100
Re: RFC: documentation of the autogroup feature [v2] Peter Zijlstra <peterz@infradead.org> - 2016-11-25 23:50 +0100
Re: RFC: documentation of the autogroup feature "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-27 22:20 +0100
Re: RFC: documentation of the autogroup feature Mike Galbraith <efault@gmx.de> - 2016-11-28 02:50 +0100
Re: RFC: documentation of the autogroup feature "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2016-11-29 10:20 +0100
Re: RFC: documentation of the autogroup feature Mike Galbraith <efault@gmx.de> - 2016-11-29 14:50 +0100
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