MIME-Version: 1.0
References: <CA+TgmoZDm5LHyLcRm2RTak_xbOcbiMyZvddZ7HSH+x-Lp9+BrQ@mail.gmail.com>
 <CAGPVpCSPoks12A1Hv_XHKTozYbtRp7uAMOag64-v_wfRkWqNxw@mail.gmail.com>
 <CA+TgmoZYS32e_t10Br3KD50vjUgr4i5yEtmcBKMeaX5AacYJDA@mail.gmail.com>
 <CAGECzQTYUhnC1bO=zNiSpUgCs=hCYxVHvLD2doXNx3My6ZAC2w@mail.gmail.com>
 <CA+TgmobpDvzyjQYX7_Y+gJFW=1_TLZt_EB71y30b0gtLBwfgAQ@mail.gmail.com>
 <CAGPVpCTN-Z9F5Wsq+LEirAv5OYZWPj1j7mE_Yumqxebsdu8YKw@mail.gmail.com>
 <CA+TgmoaMgFMkZZ7MJ=y=7rx195dZ1cViLGCVB8PP=oTGJ0eT=w@mail.gmail.com>
 <20240201032442.v3vd52kzu3hynamf@awork3.anarazel.de> <CA+TgmoagV=W=fyY2Ln_8As+Z8QJSVvnoxbgE3u+ohggxo-cMZg@mail.gmail.com>
 <CA+TgmoYs7QssFjJDUFtPkJk9U3Q_98NxWvq4sXeREZVdAyh2LQ@mail.gmail.com>
 <20240202223827.5odxkvnh4x6coe7y@awork3.anarazel.de> <CAGPVpCSX8bTF61ZL9jOgh1AaY3bgsWnQ6J7WmJK4TV0f2LPnJQ@mail.gmail.com>
 <CA+TgmoYr+ThbKThynszV1UyosewyvUF8vqY-vKeSPGXCbgoniQ@mail.gmail.com>
 <CAGECzQT9gH6uUd9pnTC=NB7TSwiTsO3kxYH5BXraSy3549Oe_g@mail.gmail.com>
 <CAApHDvoHJYcv+RCeaXM3VL6_44CgfjLLzvBbVAPvVLEMDxUdDA@mail.gmail.com>
 <CAGPVpCSCV7qtc4wjWCz2=Dad-OnJsr4zM_8Nv2qTO0HyFToNBA@mail.gmail.com>
 <CAGECzQTgup-uK9YXTM+24ib4VVk93RW_Stsh3KtHGZnrCybdyA@mail.gmail.com>
 <CAGPVpCQ-265P-DY8hZADEKE5GO0-1NVB9kn7dH82BQgEUbdv1g@mail.gmail.com> <CAApHDvoxAnbaxRnn=uEZow_xMK=dEqHHKksTHVRMtK4sNRt2_Q@mail.gmail.com>
In-Reply-To: <CAApHDvoxAnbaxRnn=uEZow_xMK=dEqHHKksTHVRMtK4sNRt2_Q@mail.gmail.com>
From: Robert Haas <robertmhaas@gmail.com>
Date: Wed, 27 Mar 2024 11:54:22 -0400
Message-ID: <CA+TgmobbAbOS7CPPC7Tj1bRy=bN738GxbxBc19RX6bw7Y02OLQ@mail.gmail.com>
Subject: Re: Flushing large data immediately in pqcomm
To: David Rowley <dgrowleyml@gmail.com>
Cc: Melih Mutlu <m.melihmutlu@gmail.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andres Freund <andres@anarazel.de>, 
	Heikki Linnakangas <hlinnaka@iki.fi>, Thomas Munro <thomas.munro@gmail.com>, 
	Jelte Fennema-Nio <postgres@jeltef.nl>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Archived-At: <https://www.postgresql.org/message-id/CA%2BTgmobbAbOS7CPPC7Tj1bRy%3DbN738GxbxBc19RX6bw7Y02OLQ%40mail.gmail.com>
Precedence: bulk

On Wed, Mar 27, 2024 at 7:39=E2=80=AFAM David Rowley <dgrowleyml@gmail.com>=
 wrote:
> Robert, I understand you'd like a bit more from this patch. I'm
> wondering if you planning on blocking another committer from going
> ahead with this? Or if you have a reason why the current state of the
> patch is not a meaningful enough improvement that would justify
> possibly not getting any improvements in this area for PG17?

So, I think that the first version of the patch, when it got a big
chunk of data, would just flush whatever was already in the buffer and
then send the rest without copying. The current version, as I
understand it, only does that if the buffer is empty; otherwise, it
copies data as much data as it can into the partially-filled buffer. I
think that change addresses most of my concern about the approach; the
old way could, I believe, lead to an increased total number of flushes
with the right usage pattern, but I don't believe that's possible with
the revised approach. I do kind of wonder whether there is some more
fine-tuning of the approach that would improve things further, but I
realize that we have very limited time to figure this out, and there's
no sense letting the perfect be the enemy of the good.

So in short... no, I don't have big concerns at this point. Melih's
latest benchmarks look fairly promising to me, too.

--=20
Robert Haas
EDB: http://www.enterprisedb.com