Re: [PATCH 2/5] progress: return early when in the background
- From
Jeff King <peff@peff.net>
- Date
- Mar 26, 2019, 05:38 UTC
- Message-ID
- <20190326053839.GC1933@sigill.intra.peff.net>
- In-Reply-To
- <20190325103844.26749-3-szeder.dev@gmail.com>
On Mon, Mar 25, 2019 at 11:38:41AM +0100, SZEDER Gábor wrote:
Show 14 quoted lines
> diff --git a/progress.c b/progress.c
> index 02a20e7d58..b57c0dae16 100644
> --- a/progress.c
> +++ b/progress.c
> @@ -86,28 +86,30 @@ static void display(struct progress *progress, uint64_t n, const char *done)
> return;
>
> progress->last_value = n;
> +
> + if (!is_foreground_fd(fileno(stderr)) && !done) {
> + progress_update = 0;
> + return;
> + }
> +Moving it here causes a measurable slowdown for:
git rev-list --progress=foo --objects --all
This function gets called for every single increment of the progress counter. Whereas in its old location:
Show 13 quoted lines
> tp = (progress->throughput) ? progress->throughput->display.buf : "";
> eol = done ? done : " \r";
> if (progress->total) {
> unsigned percent = n * 100 / progress->total;
> if (percent != progress->last_percent || progress_update) {
> progress->last_percent = percent;
> - if (is_foreground_fd(fileno(stderr)) || done) {
> - fprintf(stderr, "%s: %3u%% (%"PRIuMAX"/%"PRIuMAX")%s%s",
> - progress->title, percent,
> - (uintmax_t)n, (uintmax_t)progress->total,
> - tp, eol);
> - fflush(stderr);
> - }It was only triggered when we accumulated enough increments to print. So we save a few instructions in the backgrounded case, but it costs us a lot of extra syscalls in every other case.
According to "strace -c", the number of ioctls for that rev-list on git.git went from 6 to 373,461. But more importantly, my best-of-five timings went from 3.340s from 3.407s. That's only 2%, but it would be nice not to pay it if we don't need to.
-Peff