From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Ian Westmacott <ianw(at)intellivid(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: cost-based vacuum |
Date: | 2005-07-08 17:48:22 |
Message-ID: | 24553.1120844902@sss.pgh.pa.us |
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Lists: | pgsql-performance |
Ian Westmacott <ianw(at)intellivid(dot)com> writes:
> If I make the single configuration change of setting
> vacuum_cost_delay=1000, each iteration in analyze_thread takes
> much longer, of course. But what I also see is that the CPU
> usage of the connections for writer_thread and reader_thread
> spike up to well over 80% each (this is a dualie) and latency
> drops to 8-10s, during the ANALYZEs.
[ scratches head... ] That doesn't make any sense at all.
> I don't understand why this would be. I don't think there
> are any lock issues, and I don't see any obvious I/O issues.
> Am I missing something? Is there any way to get some
> insight into what those connections are doing?
Profiling maybe? Can you put together a self-contained test case
that replicates this behavior, so other people could look?
regards, tom lane
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