On Wednesday 04 of December 2013 08:07:23 Duy Nguyen wrote:
> On Wed, Dec 4, 2013 at 3:13 AM, Thomas Rast <tr@xxxxxxxxxxxxx> wrote:
> > Paweł Sikora <pawel.sikora@xxxxxxxx> 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.
>
> That's something to optimize, but it's single commit picking,
> sequencer_pick_revisions() should call single_pick() instead of
> pick_commits().
>
> The read+close on the whole checkout looks like there's problem with
> refresh operation and git decides to read up and verify sha-1 by
> content. Pawel, if you run "strace git update-index --refresh" twice,
> does it still show 1 stat + 1 read for every entry on the second try?
the 'git update-index --refresh' runs quickly and strace shows only lstat()
on every file. i see no massive open/read actions in this case.
$ strace -o strace-try1.log git update-index --refresh
hmdb: needs update
$ strace -o strace-try2.log git update-index --refresh
hmdb: needs update
$ grep -c lstat strace-try1.log
33793
$ grep -c lstat strace-try2.log
33793
--
gpg key fingerprint = 60B4 9886 AD53 EB3E 88BB 1EB5 C52E D01B 683B 9411
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