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| author | Manfred Spraul <manfred@colorfullife.com> | 2013-07-09 03:01:22 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-07-09 21:33:28 +0400 |
| commit | f5c936c0f267ec58641451cf8b8d39b4c207ee4d (patch) | |
| tree | 714671efc570653a64e602b70524741b0a488907 /ipc/sem.c | |
| parent | 196aa0132fc7261f34b10ae1bfb44abc1bc69b3c (diff) | |
| download | linux-f5c936c0f267ec58641451cf8b8d39b4c207ee4d.tar.xz | |
ipc/sem.c: cacheline align the semaphore structures
As now each semaphore has its own spinlock and parallel operations are
possible, give each semaphore its own cacheline.
On a i3 laptop, this gives up to 28% better performance:
#semscale 10 | grep "interleave 2"
- before:
Cpus 1, interleave 2 delay 0: 36109234 in 10 secs
Cpus 2, interleave 2 delay 0: 55276317 in 10 secs
Cpus 3, interleave 2 delay 0: 62411025 in 10 secs
Cpus 4, interleave 2 delay 0: 81963928 in 10 secs
-after:
Cpus 1, interleave 2 delay 0: 35527306 in 10 secs
Cpus 2, interleave 2 delay 0: 70922909 in 10 secs <<< + 28%
Cpus 3, interleave 2 delay 0: 80518538 in 10 secs
Cpus 4, interleave 2 delay 0: 89115148 in 10 secs <<< + 8.7%
i3, with 2 cores and with hyperthreading enabled. Interleave 2 in order
use first the full cores. HT partially hides the delay from cacheline
trashing, thus the improvement is "only" 8.7% if 4 threads are running.
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index d3ad3573bc6f..8498b67a3b62 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -96,7 +96,7 @@ struct sem { int sempid; /* pid of last operation */ spinlock_t lock; /* spinlock for fine-grained semtimedop */ struct list_head sem_pending; /* pending single-sop operations */ -}; +} ____cacheline_aligned_in_smp; /* One queue for each sleeping process in the system. */ struct sem_queue { |