On Wed, Feb 12, 2014 at 12:06 PM, Junio C Hamano <gits...@pobox.com> wrote: > Stefan Zager <sza...@chromium.org> writes: > >> ... I used the Very Sleepy profiler >> to see where all the time was spent on Windows: 55% of the time was >> spent in OpenFile, and 25% in CloseFile (both in win32). > > This is somewhat interesting. > > When we check things out, checkout_paths() has a list of paths to be > checked out, and iterates over them and call checkout_entry(). > > I wonder if you can: > > - introduce a version of checkout_entry() that takes file > descriptors to write to; > > - have an asynchronous helper threads that pre-open the paths to be > written out and feed <ce, file descriptor to be written> to a > queue; > > - restructure that loop so that it reads the <ce, file descriptor > to be written> from the queue, performs the actual writing out, > and then feeds <file descriptor to be closed> to another queue; and > > - have another asynchronous helper threads that reads <file > descriptor to be closed> from the queue and close them. > > Calls to write (and preparation of data to be written) will then > remain single-threaded, but it sounds like that codepath is not the > bottleneck in your measurement, so....
Yes, I considered that as well. At a minimum, that would still require attr.c to implement thread locking, since attribute files must be parsed to look for stream filters. I have already done that work. But I'm not sure it's the best long-term approach to add convoluted custom threading solutions to each git operation as it appears on the performance radar. I'm hoping to make the entire code base more thread-friendly, so that threading can be added in a more natural and idiomatic (and less painful) way. For example, the most natural way to add threading to checkout would be in the loops over the index in check_updates() in unpack-trees.c. If attr.c and sha1_file.c were thread-safe, then it would be possible to thread checkout entirely in check_updates(), with a pretty compact code change. I have already done the work in attr.c; sha1_file.c is hairier, but do-able. Stefan -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
