Re: Backends "hanging" with strace showing selects?

On Mon, Nov 15, 2010 at 02:52:16PM -0500, Tom Lane wrote:
> hubert depesz lubaczewski <depesz(at)depesz(dot)com> writes:
> > 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)
>
> That suggests a lot of contention for a spinlock, but without any
> information about what the system was really doing, it's hard to go
> further than that.

we had ~ 700 active connections, but it is virtually impossible to tell
what they were doing, as I couldn't connect to get pg_stat_activity.

Best regards,

depesz

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