On Thu, Dec 18, 2008, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > So instead of doing all the unpacking etc in parallel (with locking around > it to serialize it), I'd suggest doing ll the unpacking serially since > that isn't the problem anyway (and since you have to protect it with a > lock anyway), and just have a "write out and free the buffer" phase that > is done in the threads. That's certainly a more elegant way to do it, but unless I'm missing something, it requires rewriting a good bit of code. The main reason I went with the locking was to keep the patch as simple and non-intrusive as possible. > The alternative would be to actually do what your patch suggests, but > actually try to make the code git SHA1 object handling be thread-safe. At > that point, the ugly locking in write_entry() would go away, and you might > actually improve performance on SMP thanks to doing the CPU part in > parallel. I started down that path at one point, and quickly got in over my head. Making all that code thread safe looks like a big task to me. From my perspective, I get a ~350% speedup from this easy patch, and I might get an additional 25% (blind guess) from a much more difficult patch. It didn't seem worth the effort. James -- 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
