On Wed, Jan 09, 2002 at 05:09:28PM -0800, Richard Henderson wrote:
> Careful. The following is really quite a bit better on Alpha:
>
> static inline int
> sched_find_first_zero_bit(unsigned long *bitmap)
> {
> unsigned long b0 = bitmap[0];
> unsigned long b1 = bitmap[1];
> unsigned long b2 = bitmap[2];
> unsigned long ofs = MAX_RT_PRIO;
>
> if (unlikely(~(b0 & b1) != 0)) {
> b2 = (~b0 == 0 ? b0 : b1);
> ofs = (~b0 == 0 ? 0 : 64);
> }
>
> return ffz(b2) + ofs;
> }
True. Minor correction:
- b2 = (~b0 == 0 ? b0 : b1);
- ofs = (~b0 == 0 ? 0 : 64);
+ b2 = (~b0 ? b0 : b1);
+ ofs = (~b0 ? 0 : 64);
Note that comment for this function is a bit confusing:
* ... It's the fastest
* way of searching a 168-bit bitmap where the first 128 bits are
* unlikely to be set.
s/set/cleared/
> While we're on the subject of sched_find_first_zero_bit, I'd
> like to complain about Ingo's choice of header file. Why in
> the world did you choose mmu_context.h? Invent a new asm/sched.h
> if you must, but please don't choose headers at random.
Agreed. Apparently asm/bitops.h?
Ivan.
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This archive was generated by hypermail 2b29 : Tue Jan 15 2002 - 21:00:31 EST