From: Junio C Hamano <gitster@pobox.com>
Date: Mon, 14 Aug 2017 18:51:30 GMT
Subject: Re: [PATCH] cache-tree: remove use of strbuf_addf in update_one
Message-ID: <xmqqo9riugnh.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170810190349.jxlp6i7c6q5hpari@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

> On Thu, Aug 10, 2017 at 11:58:34AM -0700, Stefan Beller wrote:
>
>> On Thu, Aug 10, 2017 at 11:47 AM, Kevin Willford <kcwillford@gmail.com> wrote:
>> > String formatting can be a performance issue when there are
>> > hundreds of thousands of trees.
>> 
>> When changing this for the sake of performance, could you give
>> an example (which kind of repository you need for this to become
>> a bottleneck? I presume the large Windows repo? Or can I
>> reproduce it with a small repo such as linux.git or even git.git?)
>> and some numbers how this improves the performance?
>
> I was about to say the same thing. Normally I don't mind a small
> optimization without numbers if the result is obviously an improvement.
>
> But in this case the result is a lot less readable, and it's not
> entirely clear to me that it would always be an improvement (we now
> always run 3 strbuf calls instead of one, and have to check the length
> for each one).
>
> What I'm wondering specifically is if vsnprintf() on Kevin's platform
> (which I'll assume is Windows) is slow, and we would do better to
> replace it with a faster compat/ routine.

Yeah, I had the same reaction.