On 01/03/12 19:41, Paul Dunkler wrote:
I did that now - and analyzed the situation a bit. There are only queries running which will process very fast under high load (only index scans, very low rates of sequential scans). I found a remarkable number of Insert statements... And sometimes when that happens, the CPU Utilization is going up to nearby 100% too and 98% is system usage...
You're running on a box larger than I'm used to, so this is only speculation. I'm wondering whether you're hitting problems with lock contention or some such. It looks like you've got 48 cores there all at about 100% possibly none of them getting much chance to do any work.
Oddly, the totals you posted in your top output show 6.3% user cpu usage, which I can't make match with 50-odd processes all approaching 100% cpu.
Perhaps have a look at vmstat output too - see if context-switches spike unusually high during these periods (sorry - no idea what an unusually high number would be on a machine like yours).
Reducing the number of concurrent backends might help, but that rather depends on whether my guess is right.
If no-one more experienced than me comes along shortly, try reposting to the performance list. There are people there who are used to machines of this size.
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