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Backends "hanging" with strace showing selects?

From: hubert depesz lubaczewski <depesz(at)depesz(dot)com>
To: pgsql-general(at)postgresql(dot)org
Subject: Backends "hanging" with strace showing selects?
Date: 2010-11-15 19:35:46
Message-ID: 20101115193546.GA12381@depesz.com (view raw or flat)
Thread:
Lists: pgsql-general
hi
had strange situation today.

very high load, cpu saturated (and this machine has lots of cores).

i straced one of backends that was using lots of cpu (it was doing some
select, but I don't know what as i wasn't able to start psql).

strace looked like this:
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)
select(0, NULL, NULL, NULL, {0, 1000})  = 0 (Timeout)

i.e. lots (literally hundreds) of such messages. very quickly adding new ones.

pg version is:
 PostgreSQL 8.3.12 on x86_64-redhat-linux-gnu, compiled by GCC gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-48)


I know it's not much of information, but perhaps it will ring someones bell, and there will be ready answer what went wrong?

Best regards,

depesz


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