Am 10.08.2017 um 20:47 schrieb Kevin Willford:
> String formatting can be a performance issue when there are
> hundreds of thousands of trees.
>
> Change to stop using the strbuf_addf and just add the strings
> or characters individually.
>
> There are a limited number of modes so added a switch for the
> known ones and a default case if something comes through that
> are not a known one for git.
>
> Signed-off-by: Kevin Willford <kewi...@microsoft.com>
> ---
> cache-tree.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/cache-tree.c b/cache-tree.c
> index 2440d1dc89..41744b3db7 100644
> --- a/cache-tree.c
> +++ b/cache-tree.c
> @@ -390,7 +390,29 @@ static int update_one(struct cache_tree *it,
> continue;
>
> strbuf_grow(&buffer, entlen + 100);
> - strbuf_addf(&buffer, "%o %.*s%c", mode, entlen, path + baselen,
> '\0');
> +
> + switch (mode) {
> + case 0100644:
> + strbuf_add(&buffer, "100644 ", 7);
> + break;
> + case 0100664:
> + strbuf_add(&buffer, "100664 ", 7);
> + break;
> + case 0100755:
> + strbuf_add(&buffer, "100755 ", 7);
> + break;
> + case 0120000:
> + strbuf_add(&buffer, "120000 ", 7);
> + break;
> + case 0160000:
> + strbuf_add(&buffer, "160000 ", 7);
> + break;
You can avoid specifying the string length by using strbuf_addstr. The
compiler can determine that value; the resulting object code should be
the same with -O2.
> + default:
> + strbuf_addf(&buffer, "%o ", mode);
> + break;
> + }
> + strbuf_add(&buffer, path + baselen, entlen);
> + strbuf_addch(&buffer, '\0');
How much of the performance improvement is due to these two (especially
%.*s)? Looking forward to the perf script to find out myself. :)
> strbuf_add(&buffer, sha1, 20);
>
> #if DEBUG
>
