Re: Return of the Solaris vacuum polling problem -- anyone remember this?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Return of the Solaris vacuum polling problem -- anyone remember this?
Date: 2010-08-18 19:07:59
Message-ID: 8807.1282158479@sss.pgh.pa.us
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Josh Berkus <josh(at)agliodbs(dot)com> writes:
>> Rather, what you need to be thinking about is how
>> come vacuum seems to be making lots of pages dirty on only one of these
>> machines.

> This is an anti-wraparound vacuum, so it could have something to do with
> the hint bits. Maybe it's setting the freeze bit on every page, and
> writing them one page at a time?

That would explain all the writes, but it doesn't seem to explain why
your two servers aren't behaving similarly.

> Still don't understand the call to pollsys, even so, though.

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.

regards, tom lane

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