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Re: 16-bit page checksums for 9.2

From: Peter Geoghegan <peter(at)2ndquadrant(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Cc: Noah Misch <noah(at)leadboat(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, david(at)fetter(dot)org, aidan(at)highrise(dot)ca, stark(at)mit(dot)edu, Robert Haas <robertmhaas(at)gmail(dot)com>
Subject: Re: 16-bit page checksums for 9.2
Date: 2012-02-22 23:17:53
Message-ID: CAEYLb_VOB6OCtx_Uz_vhG_xcKBEfXDL=pVAVtoA7WAncTBSHEw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
I decided that it would be worth benchmarking this patch.
Specifically, I tested:

master, as a basis of comparison

checksum16_with_wallogged_hint_bits.v10.patch, page_checksums = 'on'

checksum16_with_wallogged_hint_bits.v10.patch, page_checksums = 'off'

This test was performed using pgbench-tools. At different client
counts and scaling factors "1,10,100", performance of an update.sql
workload was tested.

This benchmark used Greg Smith's "toy" server. As he put it recently:

"The main change to the 8 hyperthreaded core test server (Intel
i7-870) for this year is bumping it from 8GB to 16GB of RAM, which
effectively doubles the scale I can reach before things slow
dramatically." However, while Greg used scientific Linux for his
recent batch of performance numbers, the box was booted into Debian
for this, which used Kernel 2.6.32, FWIW. Didn't bother with a
separate disk for WAL.

I put shared_buffers at 1GB, and checkpoint_segments at 50. I took the
additional precaution of initdb'ing for each set, lest there be some
kind of contamination between sets, which necessitated doing some
additional work since I couldn't very well expect the "results"
database to persist. Different sets of figures from different runs
where dumped and restored, before finally being combined so that
pgbench-tools could produce it's regular report.

I have attached a config for pgbench-tools, so that others may
recreate my work here. I also attach the most relevant image,
comparing each test set across scaling levels. I'll make a pdf of the
full report available if that would be useful.

-- 
Peter Geoghegan       http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services

Attachment: scaling-sets-page-checksums.png
Description: image/png (13.6 KB) (inlined above)
Attachment: config
Description: application/octet-stream (1.3 KB)

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