Re: WIP patch for latestCompletedXid method of computing snapshot xmax

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Cc: Markus Schiltknecht <markus(at)bluegap(dot)ch>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: WIP patch for latestCompletedXid method of computing snapshot xmax
Date: 2007-09-08 21:18:34
Message-ID: 200709081418.35059.josh@agliodbs.com
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Markus,

> I've just completed two dbt2 test runs on a mid-level system, with 4GB
> RAM and a 7 disk SATA RAID 1+0 w/ BBU. Once with code as of 2007/09/05
> 18:00 (which is *before* the first lazy xid commit) and once with cvs
> HEAD (2007/09/08 +latestCompletedXid.patch.

Hmmm. Your results are withing the margin of error for DBT2, so they show no
real difference. What we need for this is a heavy-read workload, though; on
a workload like DBT2 (which is mostly writes) I wouldn't expect lazy-XID to
help much.

I'll see if I can find something appropriate. Maybe Jan's TPC-W
implementation?

--
Josh Berkus
PostgreSQL @ Sun
San Francisco

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