Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes: > On Mon, 30 Jul 2007, Craig Boston wrote: >> >> # On branch cvs_RELENG_4 >> nothing to commit (working directory clean) >> git: 67.65 seconds > > So I _seriously_ hope that about 65 of those 67 seconds was the "cvs > update -d" or something like that. > > Anything that takes a minute in git is way way *way* too slow. Any > half-way normal git operations should take less than a second. I tried a git-add . on a TeX live tree (lots of itsy files). About 80% of the processor time was wait. I think that SHA1 is costly enough that the processor(s) could get saturated when enough is done in parallel. Potential for multithreading is here enough to make any Summer of Code student weep with joy: a) one thread for opendir/readdir at every directory level b) one thread for stating the files in readdir order (more likely to correspond to the disk layout than sorted order) c) one thread on each directory level doing a mergesort on a different link field (some merge passes could be parallelized even, but let's not get overexcited) d) asynch I/O requesting the data for all files to be submitted to SHA1 e) one thread (but no more threads than there are CPUs) per independent file/tree for doing SHA1 f) asynch I/O reading the index sequentially g) one thread doing a merge pass of already sorted stuff (this can start once the top level directory has been read and sorted completely, possibly having to stop until a complete subdirectory comes in). h) asynch I/O writing out the results of the merge sequentially In fact, git-ls-files|git-add --stdin is already exploiting a bit of parallelism (and will probably profit from CFS by making much more use of the buffering capacity of the pipe). It is counterintuitive that hand-built chains work more efficiently than explicit git commands. -- David Kastrup, Kriemhildstr. 15, 44793 Bochum - 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
