From: PFC <lists@peufeu.com>
To: Ross J. Reedstrom <reedstrm@rice.edu>
To: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: TCP network cost
Date: Thu, 19 Feb 2009 14:09:04 +0100
Message-ID: <op.upln5emacigqcu@soyouz> (raw)
In-Reply-To: <20090217211454.GB23707@cooker>
References: <20090217070403.GB2486@cooker>
<1ca1c1410902171013q478f2620n13fcd68cb8b3d911@mail.gmail.com>
<3FAF940B-9B0B-4DBA-8728-6096022129DF@infogears.com>
<alpine.DEB.1.10.0902170032440.25606@asgard.lang.hm>
<20090217200416.GA23707@cooker>
<B7A2E4DA-A137-46F5-8643-2EF3772F4D2C@infogears.com>
<20090217211454.GB23707@cooker>
> python w/ psycopg (or psycopg2), which wraps libpq. Same results w/
> either version.
I've seen psycopg2 saturate a 100 Mbps ethernet connection (direct
connection with crossover cable) between postgres server and client during
a benchmark... I had to change the benchmark to not retrieve a large TEXT
column to remove this bottleneck... this was last year so versions are
probably different, but I don't think this matters a lot...
> Note the 'bare' transfer times added above. Nothing to write home about
> (~3Mb/sec) but another order of magnitude faster than the postgresql
> transfer.
You should test with sending a large (>100 MB) amount of data through
Netcat. This should give you your maximum wire speed. Use /dev/null as the
test file, and use "pv" (pipe viewer) to measure throughput :
box 1 : pv < /dev/zero | nc -lp 12345
box 2 : nc (ip) 12345 >/dev/null
On gigabit lan you should get 100 MB/s, on 100BaseT about 10 MB/s. If you
dont get that, there is a problem somewhere (bad cable, bad NIC, slow
switch/router, etc). Monitor CPU during this test (vmstat). Usage should
be low.
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: lists@peufeu.com, reedstrm@rice.edu
Subject: Re: TCP network cost
In-Reply-To: <op.upln5emacigqcu@soyouz>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox