Re: slow git-cherry-pick.

From: Thomas Rast <tr@thomasrast.ch>
Date: Dec 3, 2013, 20:13 UTC
Message-ID: <87fvq9n154.fsf@linux-1gf2.Speedport_W723_V_Typ_A_1_00_098>
In-Reply-To: <2142926.gg3W3MsbJZ@localhost.localdomain>

Paweł Sikora <pawel.sikora@agmk.net> writes:

Umm, there's a gem here that the thread missed so far:

> my git repo isn't very big[1] but it's checked out on the linear lvm
> where random i/o generally hurts and strace shows that current git version
> performs 2x{lstat}+1x{open,read,close} [2] on whole checkout before

           ^^^^^^^^^

There's no reason why it should do the lstat() *twice* for every file. But Paweł is right; the code path roughly goes like this:

int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
{
[...]
	res = sequencer_pick_revisions(&opts);

int sequencer_pick_revisions(struct replay_opts *opts)
{
[...]
	read_and_refresh_cache(opts);
[...]
	return pick_commits(todo_list, opts);
}

static int pick_commits(struct commit_list *todo_list, struct replay_opts *opts)
{
[...]
	read_and_refresh_cache(opts);

I'm too tired to dig further, but AFAICT it's just a rather obvious case of duplication of effort.

-- 
Thomas Rast
tr@thomasrast.ch