Messages in this thread | | | Date | Wed, 25 Nov 2009 07:17:28 -0700 | From | Matthew Wilcox <> | Subject | Re: [PATCH 2/3]fs/inode: iunique() Optimize Performance |
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On Wed, Nov 25, 2009 at 10:12:19PM +0800, Liuweni wrote: > @@ -605,8 +605,8 @@ static unsigned long hash(struct super_block *sb, unsigned long hashval) > { > unsigned long tmp; > > - tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) / > - L1_CACHE_BYTES; > + tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) >> > + L1_CACHE_SHIFT; > tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS); > return tmp & I_HASHMASK; > }
Have you compared the compiler output before/after your change? I'd be amazed if GCC isn't able to optimise division-by-a-constant-power-of-two into shift-by-constant.
-- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."
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