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authorManfred Spraul <manfred@colorfullife.com>2013-07-08 16:01:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-09 10:33:28 -0700
commitf5c936c0f267ec58641451cf8b8d39b4c207ee4d (patch)
tree714671efc570653a64e602b70524741b0a488907
parent196aa0132fc7261f34b10ae1bfb44abc1bc69b3c (diff)
downloadlinux-stericsson-f5c936c0f267ec58641451cf8b8d39b4c207ee4d.tar.gz
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>
-rw-r--r--ipc/sem.c2
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 {