| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Richard Huxton <dev(at)archonet(dot)com> |
| Cc: | Jason Lustig <lustig(at)brandeis(dot)edu>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Autovacuum running out of memory |
| Date: | 2007-10-16 15:38:56 |
| Message-ID: | 17244.1192549136@sss.pgh.pa.us |
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| Thread: | |
| Lists: | pgsql-performance |
I wrote:
> ... The weird thing about this
> is why the large maintenance_work_mem works for a regular session and
> not for autovacuum. There really shouldn't be much difference in the
> maximum workable setting for the two cases, AFAICS.
After re-reading the thread I realized that the OP is comparing manual
VACUUM FULL to automatic plain VACUUM, so the mystery is solved.
Plain VACUUM tries to grab a maintenance_work_mem-sized array of
tuple IDs immediately at command startup. VACUUM FULL doesn't work
like that.
Given the 200M ulimit -v, and the shared_buffers setting of 20000
(about 160M), the behavior is all explained if we assume that shared
memory counts against -v. Which I think it does.
regards, tom lane
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