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authorLinus Torvalds <torvalds@linux-foundation.org>2012-09-16 23:29:43 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-09-16 23:29:43 +0400
commit37407ea7f93864c2cfc03edf8f37872ec539ea2b (patch)
tree7c07e7adadd40fc94cebfe816f1c65a4a630b147 /include
parent3f0c3c8fe30c725c1264fb6db8cc4b69db3a658a (diff)
downloadlinux-37407ea7f93864c2cfc03edf8f37872ec539ea2b.tar.xz
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')
-rw-r--r--include/linux/sched.h1
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 */