On 12/15/2010 06:06 AM, Nick Piggin wrote: > > However instead of a normal memcmp, we could actually pad dentry > names out to sizeof(long) with zeros, and take advantage of that with > a memcmp that does not have to handle tails -- it would operate > entirely with longs. > > That would avoid icache and branch regressions, and might speed up > the operation on some architectures. I just doubted whether it would > show an improvement to be worth doing at all. If it does, I'm all for it. > I agree that the byte-compare or long-compare should give you very close results in modern pipeline CPUs. But surly 12 increments-and-test should show up against 3 (or even 2). I would say it must be a better plan. BTW the long approach if you assume that the beginning of the string is long aligned than it is only a matter of comparing the last byte with a mask, no branches. But I'm not saying, just make sure they are padded. Just my $0.017 Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
