Messages in this thread Patch in this message | | | From | Manfred Spraul <> | Subject | [PATCH 2/6] ipc/sem.c: cacheline align the semaphore structures | Date | Mon, 10 Jun 2013 19:16:47 +0200 |
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As now each semaphore has it's own spinlock and parallel operations are possible, give each semaphore it's 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.
Andrew: Could you merge it into -akpm and then forward it towards Linus' tree?
Signed-off-by: Manfred Spraul <manfred@colorfullife.com> --- ipc/sem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/ipc/sem.c b/ipc/sem.c index 70480a3..1afbc57 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 { -- 1.8.1.4
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