Re: Understand this error

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>
Cc: paulo matadr <saddoness(at)yahoo(dot)com(dot)br>, GENERAL <pgsql-general(at)postgresql(dot)org>
Subject: Re: Understand this error
Date: 2009-05-01 15:50:21
Message-ID: 13161.1241193021@sss.pgh.pa.us
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Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> writes:
> Note that it's not very likely that PostgreSQL was the process that used
> up all your memory. It was just unlucky enough to be picked as the one
> to be killed, because the OOM killer is terrible at estimating which
> process is using the most memory when programs like PostgreSQL have
> allocated large blocks of shared memory.

It's worse than that: the OOM killer is broken by design, because it
intentionally picks on processes that have a lot of large children
--- without reference to the fact that a lot of the "largeness" might
be the same shared memory block. So the postmaster process very often
looks like a good target to it, even though killing the postmaster will
in fact free a negligible amount of memory.

regards, tom lane

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