From: Junio C Hamano <gitster@pobox.com>
Date: Mon, 19 Oct 2020 17:23:26 GMT
Subject: Re: [PATCH 1/4] fsmonitor: use fsmonitor data in `git diff`
Message-ID: <xmqqr1puuo35.fsf@gitster.c.googlers.com>
In-Reply-To: <20201018234344.GC4204@nand.local>

Taylor Blau <me@ttaylorr.com> writes:

>> > There is some overhead to invoke the hook and talk to watchman, but
>> > I'd expect that to be dwarfed by not having to issue O(# files)
>> > syscalls.
>>
>> "invoke the hook"---is that a pipe+fork+exec, or something else that
>> is far lighter-weight?
>
> The former; see 'fsmonitor.c:query_fsmonitor()'.

It brings us back to the "overhead of how many lstat(2) takes us
closer to the overhead of a single pipe+fork+exec plus reading from
the pipe", doesn't it?