From: Josh Berkus <josh@agliodbs.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Return of the Solaris vacuum polling problem -- anyone remember this?
Date: Wed, 18 Aug 2010 13:31:23 -0700
Message-ID: <4C6C431B.9010406@agliodbs.com> (raw)
In-Reply-To: <8807.1282158479@sss.pgh.pa.us>
References: <4C69827A.409@agliodbs.com>
<19969.1281986537@sss.pgh.pa.us>
<4C6C2B2B.9060501@agliodbs.com>
<8599.1282158010@sss.pgh.pa.us>
<4C6C2E4A.1010506@agliodbs.com>
<8807.1282158479@sss.pgh.pa.us>
> That would explain all the writes, but it doesn't seem to explain why
> your two servers aren't behaving similarly.
Well, that's why I said "ostensibly identical". There may in fact be
differences, not just in the databases but in some OS libs as well.
These servers have been in production for quite a while, and the owner
has a messy deployment process.
> Most likely that's the libc implementation of the select()-based sleeps
> for vacuum_cost_delay. I'm still suspicious that the writes are eating
> more cost_delay points than you think.
Tested that. It does look like if I increase vacuum_cost_limit to 10000
and lower vacuum_cost_page_dirty to 10, it reads 5-7 pages and writes
2-3 before each pollsys. The math seems completely wrong on that,
though -- it should be 50 and 30 pages, or similar. If I can, I'll test
a vacuum without cost_delay and make sure the pollsys() are connected to
the cost delay and not something else.
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com
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To: pgsql-hackers@postgresql.org
Cc: josh@agliodbs.com, tgl@sss.pgh.pa.us
Subject: Re: Return of the Solaris vacuum polling problem -- anyone remember this?
In-Reply-To: <4C6C431B.9010406@agliodbs.com>
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