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authorNick Piggin <npiggin@suse.de>2006-10-11 04:21:52 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-11 14:14:22 -0400
commitbeed33a816204cb402c69266475b6a60a2433ceb (patch)
tree4eaa7e5a1ccf2960d1478774cdfcab671384accb /include/asm-generic
parentf33d9bd50478c9a969b65f58feb6b69a3ad478cb (diff)
[PATCH] sched: likely profiling
This likely profiling is pretty fun. I found a few possible problems in sched.c. This patch may be not measurable, but when I did measure long ago, nooping (un)likely cost a couple of % on scheduler heavy benchmarks, so it all adds up. Tweak some branch hints: - the 2nd 64 bits in the bitmask is likely to be populated, because it contains the first 28 bits (nearly 3/4) of the normal priorities. (ratio of 669669:691 ~= 1000:1). - it isn't unlikely that context switching switches to another process. it might be very rapidly switching to and from the idle process (ratio of 475815:419004 and 471330:423544). Let the branch predictor decide. - preempt_enable seems to be very often called in a nested preempt_disable or with interrupts disabled (ratio of 3567760:87965 ~= 40:1) Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Daniel Walker <dwalker@mvista.com> Cc: Hua Zhong <hzhong@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/bitops/sched.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/asm-generic/bitops/sched.h b/include/asm-generic/bitops/sched.h
index 5ef93a4d009f..815bb0148060 100644
--- a/include/asm-generic/bitops/sched.h
+++ b/include/asm-generic/bitops/sched.h
@@ -15,7 +15,7 @@ static inline int sched_find_first_bit(const unsigned long *b)
15#if BITS_PER_LONG == 64 15#if BITS_PER_LONG == 64
16 if (unlikely(b[0])) 16 if (unlikely(b[0]))
17 return __ffs(b[0]); 17 return __ffs(b[0]);
18 if (unlikely(b[1])) 18 if (likely(b[1]))
19 return __ffs(b[1]) + 64; 19 return __ffs(b[1]) + 64;
20 return __ffs(b[2]) + 128; 20 return __ffs(b[2]) + 128;
21#elif BITS_PER_LONG == 32 21#elif BITS_PER_LONG == 32