On 2/4/2020 4:24 PM, René Scharfe wrote:
> We can calculate the size of new name easily and precisely. Open-code
> the xstrfmt() calls and grow the buffers as needed before filling them.
> This provides a surprisingly large benefit when working with the
> Chromium repository; here are the numbers measured using hyperfine
> before:
>
> Benchmark #1: ./git -C ../chromium/src name-rev --all
> Time (mean ± σ): 5.822 s ± 0.013 s [User: 5.304 s, System: 0.516 s]
> Range (min … max): 5.803 s … 5.837 s 10 runs
>
> ... and with this patch:
>
> Benchmark #1: ./git -C ../chromium/src name-rev --all
> Time (mean ± σ): 1.527 s ± 0.003 s [User: 1.015 s, System: 0.511 s]
> Range (min … max): 1.524 s … 1.535 s 10 runs
Nice!
> + if (name->generation > 0) {
> + strbuf_grow(&sb, len +
> + 1 + decimal_width(name->generation) +
> + 1 + decimal_width(parent_number));
Just curious: these strbuf_grow() calls are what _really_ improve the
performance, right? If you dropped them, then can we expect the performance
to be similar to the old code?
> + strbuf_addf(&sb, "%.*s~%d^%d", (int)len, name->tip_name,
> + name->generation, parent_number);
> + } else {
> + strbuf_grow(&sb, len +
> + 1 + decimal_width(parent_number));
> + strbuf_addf(&sb, "%.*s^%d", (int)len, name->tip_name,
> + parent_number);
> + }
> + return strbuf_detach(&sb, NULL);
> }
>
> static void name_rev(struct commit *start_commit,
> --
> 2.25.0
>
