René Scharfe <rene.scharfe@xxxxxxxxxxxxxx> writes: > I get this (Ubuntu 8.10 x64, Fedora 10 x64 using the same Linux repo, > Windows Vista x64 using a different Linux repo with the same HEAD on > NTFS and msysgit, numbers are the elapsed time in seconds, best of five > runs): > > Ubuntu Fedora Windows > v1.6.2-rc2 8.14 8.16 9.236 > v1.6.2-rc2+[1-4] 2.43 2.45 2.995 > v1.6.2-rc2+[1-4]+memmem 1.31 1.25 2.917 > v1.6.2-rc2+[1-3]+memmem 1.51 1.16 8.455 > > Ubuntu has glibc 2.8, while Fedora 10 has glibc 2.9, with a new and more > efficient memmem() implementation. On Windows, we use our own naive > memmem() implementation. Shoot, I was not being careful enough. > So using memmem() is worthwhile. And providing a better fall-back > version in compat/ can speed up this particular case to the point where > the fourth patch becomes moot. Are these numbers telling me that with a good memmem() implementation, patch 4/4 is not just moot but actively detrimental? With a long enough needle, it entirely is possible that scanning the whole image with sublinear string search algorithm would perform much better than the preprocessing patch 4/4 does which has to scan all the bytes in the common parts. -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
