Commit a75f5f0f authored by Matt Turner's avatar Matt Turner Committed by Matt Turner
Browse files

alpha: simplify and optimize sched_find_first_bit



Search only the first 100 bits instead of 140, saving a couple
instructions. The resulting code is about 1/3 faster (40K ticks/1000
iterations down to 30K ticks/1000 iterations).

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: linux-alpha@vger.kernel.org
Acked-by: default avatarRichard Henderson <rth@twiddle.net>
Signed-off-by: default avatarMatt Turner <mattst88@gmail.com>
parent 1cb3d8e2
......@@ -438,22 +438,20 @@ static inline unsigned int __arch_hweight8(unsigned int w)
/*
* Every architecture must define this function. It's the fastest
* way of searching a 140-bit bitmap where the first 100 bits are
* unlikely to be set. It's guaranteed that at least one of the 140
* bits is set.
* way of searching a 100-bit bitmap. It's guaranteed that at least
* one of the 100 bits is cleared.
*/
static inline unsigned long
sched_find_first_bit(unsigned long b[3])
sched_find_first_bit(const unsigned long b[2])
{
unsigned long b0 = b[0], b1 = b[1], b2 = b[2];
unsigned long ofs;
unsigned long b0, b1, ofs, tmp;
ofs = (b1 ? 64 : 128);
b1 = (b1 ? b1 : b2);
ofs = (b0 ? 0 : ofs);
b0 = (b0 ? b0 : b1);
b0 = b[0];
b1 = b[1];
ofs = (b0 ? 0 : 64);
tmp = (b0 ? b0 : b1);
return __ffs(b0) + ofs;
return __ffs(tmp) + ofs;
}
#include <asm-generic/bitops/ext2-non-atomic.h>
......
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