This is a note to let you know that I've just added the patch titled
sched/autogroup: Fix 64-bit kernel nice level adjustment
to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-autogroup-fix-64-bit-kernel-nice-level-adjustment.patch
and it can be found in the queue-4.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 83929cce95251cc77e5659bf493bd424ae0e7a67 Mon Sep 17 00:00:00 2001
From: Mike Galbraith <efault@xxxxxx>
Date: Wed, 23 Nov 2016 11:33:37 +0100
Subject: sched/autogroup: Fix 64-bit kernel nice level adjustment
From: Mike Galbraith <efault@xxxxxx>
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@xxxxxxxxx>
Tested-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Signed-off-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-man <linux-man@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1479897217.4306.6.camel@xxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from efault@xxxxxx are
queue-4.8/sched-autogroup-fix-64-bit-kernel-nice-level-adjustment.patch
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