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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2012-09-16 12:29:43 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-09-16 12:29:43 -0700 |
| commit | 37407ea7f93864c2cfc03edf8f37872ec539ea2b (patch) | |
| tree | 7c07e7adadd40fc94cebfe816f1c65a4a630b147 /include/linux/sched.h | |
| parent | 3f0c3c8fe30c725c1264fb6db8cc4b69db3a658a (diff) | |
| download | lwn-37407ea7f93864c2cfc03edf8f37872ec539ea2b.tar.gz lwn-37407ea7f93864c2cfc03edf8f37872ec539ea2b.zip | |
Revert "sched: Improve scalability via 'CPU buddies', which withstand random perturbations"
This reverts commit 970e178985cadbca660feb02f4d2ee3a09f7fdda.
Nikolay Ulyanitsky reported thatthe 3.6-rc5 kernel has a 15-20%
performance drop on PostgreSQL 9.2 on his machine (running "pgbench").
Borislav Petkov was able to reproduce this, and bisected it to this
commit 970e178985ca ("sched: Improve scalability via 'CPU buddies' ...")
apparently because the new single-idle-buddy model simply doesn't find
idle CPU's to reschedule on aggressively enough.
Mike Galbraith suspects that it is likely due to the user-mode spinlocks
in PostgreSQL not reacting well to preemption, but we don't really know
the details - I'll just revert the commit for now.
There are hopefully other approaches to improve scheduler scalability
without it causing these kinds of downsides.
Reported-by: Nikolay Ulyanitsky <lystor@gmail.com>
Bisected-by: Borislav Petkov <bp@alien8.de>
Acked-by: Mike Galbraith <efault@gmx.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/sched.h')
| -rw-r--r-- | include/linux/sched.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index b8c86648a2f9..23bddac4bad8 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -954,7 +954,6 @@ struct sched_domain { unsigned int smt_gain; int flags; /* See SD_* */ int level; - int idle_buddy; /* cpu assigned to select_idle_sibling() */ /* Runtime fields. */ unsigned long last_balance; /* init to jiffies. units in jiffies */ |