From: Jeff King <peff@peff.net>
Date: Thu, 11 Mar 2021 20:53:56 GMT
Subject: Re: [PATCH v5 01/12] pkt-line: eliminate the need for static buffer in packet_write_gently()
Message-ID: <YEqDZP/Ea+qf0Qrp@coredump.intra.peff.net>
In-Reply-To: <xmqq4khhctya.fsf@gitster.g>

On Thu, Mar 11, 2021 at 12:32:29PM -0800, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > On Tue, Mar 09, 2021 at 03:48:40PM -0800, Junio C Hamano wrote:
> >
> >> "Jeff Hostetler via GitGitGadget" <gitgitgadget@gmail.com> writes:
> >> 
> >> > +	/*
> >> > +	 * Write the header and the buffer in 2 parts so that we do not need
> >> > +	 * to allocate a buffer or rely on a static buffer.  This avoids perf
> >> > +	 * and multi-threading issues.
> >> > +	 */
> >> 
> >> I understand "multi-threading issues" (i.e. let's not have too much
> >> stuff on the stack), but what issue around "perf" are we worried
> >> about?
> >>  ...
> > Yeah, this came from my suggestion. My gut feeling is that it isn't
> > likely to matter, but I'd much rather solve any performance problem we
> > find using writev(), which would be pretty easy to emulate with a
> > wrapper for systems that lack it.
> 
> I too had writev() in mind when I said "can fix it locally", so we
> are on the same page, which is good.
> 
> So "this avoid multi-threading issues" without mentioning "perf and"
> would be more appropriate?

IMHO yes. I think "avoid perf issues" is probably answering the "why not
just heap-allocate the buffer" question. But that makes sense in the
commit message, not in a comment.

-Peff