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@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-alpha@xxxxxxxxxxxxxxx
Signed-off-by: Matt Turner <mattst88@xxxxxxxxx>
---
arch/alpha/include/asm/bitops.h | 20 +++++++++-----------
1 files changed, 9 insertions(+), 11 deletions(-)
diff --git a/arch/alpha/include/asm/bitops.h b/arch/alpha/include/asm/bitops.h
index 15f3ae2..2e49c1f 100644
--- a/arch/alpha/include/asm/bitops.h
+++ b/arch/alpha/include/asm/bitops.h
@@ -436,22 +436,20 @@ static inline unsigned int 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>
--
1.6.5.3
--
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