Jakub Ouhrabka <kuba@comgate.cz> writes:
> we have a PostgreSQL dedicated Linux server with 8 cores (2xX5355). We
> came accross a strange issue: when running with all 8 cores enabled
> approximatly once a minute (period differs) the system is very busy for
> a few seconds (~5-10s) and we don't know why - this issue don't show up
> when we tell Linux to use only 2 cores, with 4 cores the problem is here
> but it is still better than with 8 cores - all on the same machine, same
> config, same workload. We don't see any apparent reason for these peaks.
Interesting. Maybe you could use oprofile to try to see what's
happening? It sounds a bit like momentary contention for a spinlock,
but exactly what isn't clear.
> Can this be connected with our heavy use of listen/notify and hundreds
> backends in listen mode?
Perhaps. Have you tried logging executions of NOTIFY to see if they are
correlated with the spikes?
regards, tom lane