Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.8 13/33] sched/autogroup: Fix 64-bit kernel nice level adjustment | Date | Tue, 13 Dec 2016 09:16:14 -0800 |
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4.8-stable review patch. If anyone has any objections, please let me know.
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From: Mike Galbraith <efault@gmx.de>
commit 83929cce95251cc77e5659bf493bd424ae0e7a67 upstream.
Michael Kerrisk reported:
> Regarding the previous paragraph... My tests indicate > that writing *any* value to the autogroup [nice priority level] > file causes the task group to get a lower priority.
Because autogroup didn't call the then meaningless scale_load()...
Autogroup nice level adjustment has been broken ever since load resolution was increased for 64-bit kernels. Use scale_load() to scale group weight.
Michael Kerrisk tested this patch to fix the problem:
> Applied and tested against 4.9-rc6 on an Intel u7 (4 cores). > Test setup: > > Terminal window 1: running 40 CPU burner jobs > Terminal window 2: running 40 CPU burner jobs > Terminal window 1: running 1 CPU burner job > > Demonstrated that: > * Writing "0" to the autogroup file for TW1 now causes no change > to the rate at which the process on the terminal consume CPU. > * Writing -20 to the autogroup file for TW1 caused those processes > to get the lion's share of CPU while TW2 TW3 get a tiny amount. > * Writing -20 to the autogroup files for TW1 and TW3 allowed the > process on TW3 to get as much CPU as it was getting as when > the autogroup nice values for both terminals were 0.
Reported-by: Michael Kerrisk <mtk.manpages@gmail.com> Tested-by: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-man <linux-man@vger.kernel.org> Link: http://lkml.kernel.org/r/1479897217.4306.6.camel@gmx.de Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/sched/auto_group.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/kernel/sched/auto_group.c +++ b/kernel/sched/auto_group.c @@ -192,6 +192,7 @@ int proc_sched_autogroup_set_nice(struct { static unsigned long next = INITIAL_JIFFIES; struct autogroup *ag; + unsigned long shares; int err; if (nice < MIN_NICE || nice > MAX_NICE) @@ -210,9 +211,10 @@ int proc_sched_autogroup_set_nice(struct next = HZ / 10 + jiffies; ag = autogroup_task_get(p); + shares = scale_load(sched_prio_to_weight[nice + 20]); down_write(&ag->lock); - err = sched_group_set_shares(ag->tg, sched_prio_to_weight[nice + 20]); + err = sched_group_set_shares(ag->tg, shares); if (!err) ag->nice = nice; up_write(&ag->lock);
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