On Thu, Feb 19, 2009 at 02:09:04PM +0100, PFC wrote: > > >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... Here's the core of the problem: I in fact need to transfer exactly that: a large single field (bytea in my case). I suspect psycopg[12] is having issues w/ memory allocation, but that's just an unsupported gut feeling. The final upshot is that I need to restructure my config to use the large-object API (and hence a snapshot of psycopg2) to get decent throughput. > 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. 112 MB/s, and 233 MB/s for localhost. Thanks for the pointer to pv: looks like a nice tool. Investigating this problem has lead me to a number of nice 'old school' tools: the other is tcptrace and xplot.org. I've been hand reading tcpdump output, or clicking around in ethereal/wireshark. I like tcptrace's approach. Ross -- Ross Reedstrom, Ph.D. reedstrm@xxxxxxxx Systems Engineer & Admin, Research Scientist phone: 713-348-6166 The Connexions Project http://cnx.org fax: 713-348-3665 Rice University MS-375, Houston, TX 77005 GPG Key fingerprint = F023 82C8 9B0E 2CC6 0D8E F888 D3AE 810E 88F0 BEDE -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
