Messages in this thread | | | Date | Sun, 6 Jan 2002 19:16:31 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [announce] [patch] ultra-scalable O(1) SMP and UP scheduler |
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On Sun, 6 Jan 2002, Richard Henderson wrote: > On Sun, Jan 06, 2002 at 02:13:32AM +0000, Alan Cox wrote: > > ... since an 8bit ffz can be done by lookup table > > and that is fast on all processors > > Please still provide the arch hook -- single cycle ffs type > instructions are still faster than any memory access.
This is probably true even on x86, except in benchmarks (the x86 ffs instruction definitely doesn't historically count as "fast", and a table lookup will probably win in a benchmark where the table is hot in the cache, but you don't have to miss very often to be ok with a few CPU cycles..)
(bsfl used to be very slow. That's not as true any more)
Linus
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