Re: [PATCH] setup: avoid unconditional open with write flags

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 6, 2022, 00:10 UTC
Message-ID: <xmqq7cz5pf1w.fsf@gitster.g>
In-Reply-To: <Y453yiYAifv/oV5n@nand.local>

Taylor Blau <me@ttaylorr.com> writes:

Show 6 quoted lines

> So it appears that the old version is ever-so-slightly faster than the
> new one. But it's so noisy, and the regression is so small that it's
> hard to notice it at all.
>
> So I wouldn't strongly oppose the patch based on those numbers, but in
> principle it seems flawed.

Thanks for writing and reviewing.

As long as we were touching the function, I suspect that the logic should become more like

    if (fd #0 is not open)
	open /dev/null read-only and give it to fd #0
    if (fd #1 is not open)
	open /dev/null write-only and give it to fd #1
    if (fd #2 is not open)
	open /dev/null write-only and give it to fd #2

with opening of /dev/null optimized not to happen when not needed.