Re: [git wiki PATCH 1/3] "Improving parallelism in various commands" project

[Resend since the first try had HTML and the list rejected it]

On Fri, Mar 2, 2012, Thomas Rast <trast@student.ethz.ch> wrote:
+ * In preparation (the half-step): identify commands that could
+   benefit from parallelism.  `git grep --cached` and `git grep
+   COMMIT` come to mind, but most likely also `git diff` and `git log
+   -p`.  You can probably find more.

For those of us who must work on NFS for various reasons, it would help tremendously to write out work tree files in parallel, during 'git clone', 'git reset --hard', and any other command that writes lots of files to the work tree. You can get a huge speedup (benchmarked at ~3.5x) without even unpacking those files in parallel; unpacking them serially and writing them to disk in parallel is sufficient.

I submitted a patch [1] ~2 years ago that added that capability. It was not accepted, but it did demonstrate the huge potential speedup on NFS, and the pitfall of degrading performance on a local drive. The patch itself is probably not useful any more, but it includes some benchmarks, and the discussion may be helpful.

James

[1] http://thread.gmane.org/gmane.comp.version-control.git/103489