On 7/13/2021 3:33 PM, Elijah Newren via GitGitGadget wrote:
> From: Elijah Newren <newren@xxxxxxxxx>
...
> For the testcases mentioned in commit 557ac0350d ("merge-ort: begin
> performance work; instrument with trace2_region_* calls", 2020-10-28),
> this change improves the performance as follows:
>
> Before After
> no-renames: 5.235 s ± 0.042 s 205.1 ms ± 3.8 ms
Wow! This is quite the savings, and reinforces that when no renames
exist we are likely to hit this optimization.
> mega-renames: 9.419 s ± 0.107 s 1.564 s ± 0.010 s
I'm surprised that this one works so well, too. Clearly, there must
be a lot of directories that can be skipped despite many renames
existing.
> just-one-mega: 480.1 ms ± 3.9 ms 479.5 ms ± 3.9 ms
And no overhead added to this case. Good.
> + /* Loop over the set of paths we need to know rename info for */
> + strset_for_each_entry(&renames->relevant_sources[side],
> + &iter, entry) {
> + char *rename_target, *dir, *dir_marker;
> + struct strmap_entry *e;
> +
> + /*
> + * if we don't know delete/rename info for this path,
> + * then we need to recurse into all trees to get all
> + * adds to make sure we have it.
> + */
super-nit: s/if/If/
Otherwise, I can't speak to the code being 100% correct because
this area is so dense. I find the code to be well organized,
which will help finding and fixing any potential bugs that might
show up in strange corner cases later.
Thanks,
-Stolee
