On Tue, Oct 13, 2020 at 12:40:47AM +0000, Elijah Newren via GitGitGadget wrote:
> From: Elijah Newren <newren@xxxxxxxxx>
>
> When strmaps are used heavily, such as is done by my new merge-ort
> algorithm, and strmaps need to be cleared but then re-used (because of
> e.g. picking multiple commits to cherry-pick, or due to a recursive
> merge having several different merges while recursing), free-ing and
> reallocating map->table repeatedly can add up in time, especially since
> it will likely be reallocated to a much smaller size but the previous
> merge provides a good guide to the right size to use for the next merge.
>
> Introduce strmap_partial_clear() to take advantage of this type of
> situation; it will act similar to strmap_clear() except that
> map->table's entries are zeroed instead of map->table being free'd.
> Making use of this function reduced the cost of reset_maps() by about
> 20% in mert-ort, and dropped the overall runtime of my rebase testcase
> by just under 2%.
Oh, these were the real numbers I was looking for earlier. :)
Of course it's a little confusing because reset_maps() doesn't exist yet
in the code base this is being applied on, but I can live with that.
> +/*
> + * Similar to strmap_clear() but leaves map->map->table allocated and
> + * pre-sized so that subsequent uses won't need as many rehashings.
> + */
> +void strmap_partial_clear(struct strmap *map, int free_values);
Oh good, you anticipated my free_values suggestion from earlier. But...
> +void strmap_partial_clear(struct strmap *map, int free_util)
> +{
> + strmap_free_entries_(map, free_util);
> + hashmap_partial_clear(&map->map);
> +}
...the implementation didn't catch up.
Other than that the patch looks obviously correct.
-Peff
