Re: Occasional giant spikes in CPU load

Craig James wrote:
> I managed to capture one such event using top(1) with the "batch"
> option as a background process. See output below

You should add "-c" to your batch top capture, then you'll be able to
see what the individual postmaster processes are actually doing when
things get stuck.

> max_connections = 1000
> shared_buffers = 2000MB
> work_mem = 256MB
> Mem: 8194800k total, 8118688k used, 76112k free, 36k buffers
> Swap: 2031608k total, 169348k used, 1862260k free, 7313232k cached

These settings appear way too high for a server with 8GB of RAM. I'm
not sure if max_connections is too large, or if it's work_mem that's too
big, but one or both of them may need to be tuned way down from where
they are now to get your memory usage under control. Your server might
running out of RAM during the periods where it becomes
unresponsive--that could be the system paging stuff out to swap, which
isn't necessarily a high user of I/O but it will block things. Not
having any memory used for buffers is never a good sign.

--
Greg Smith 2ndQuadrant US Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com www.2ndQuadrant.us