Re: pgbench: spike in pgbench results(graphs) while testing pg_hint_plan performance

On 5/23/13 7:39 AM, Sachin D. Bhosale-Kotwal wrote:
> So i am not getting why spike occure at *12:09:14 *only*.*

This could easily be caused by something outside of the test itself.
Background processes. A monitoring system kicking in to write some data
to disk will cause a drop like this.

Three things you could look into to try and track down the issue:

-Did you turn on log_checkpoints to see if one happens to run when the
rate drops? If so, that could be the explanation. Looks like you setup
the test to make this less likely, but checkpoints are tough to
eliminate altogether.

-Does this happen on every test run? Is it at the same time?

-You can run "top -bc" to dump snapshots of what the system is doing
every second. With some work you can then figure out what was actually
happening during the two seconds around when the throughput dropped.

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