[pgpool-general: 1528] Mysterious Load Spikes

[Quentin Hartman]

We've been happily using the pgpool2 3.1.1 packages from Ubuntu 12.04 on
Ubuntu 11.04 for nearly a year. We needed features in 3.1 and backporting
the packages was the most clean and expedient way to get that version.

We recently upgraded the distribution on those servers to 12.04, so we are
still running the same pgpool2 packages, but now we have this mysterious
"phantom load" on those boxes.

Under the same workload as they had before, they now are spiking to 5 or 10
load (these are dual core machines) every few minutes with no perceivable
explanation. There is no process consuming CPU, plenty of RAM is available,
and there is negligible disk IO. It may be worth mentioning these are
virtualized machines running on Amazon EC2, and the steal rate is also very
low, so I don't think there is something external to the machines causing
the problem. Additionally, this upgrade was performed on nearly 40 machines
in this cluster, and only the ones running pgpool2 are showing this
behavior, so I'm confident it's related to pgpool2.

I've seen at least one other post on the list mentioning this problem, but
no resolution.

Is this something anyone else has seen? Is there anything that has changed
in the newer releases that is likely to affect this? My suspicion is that
something changed in the 3.x kernel series that pgpool2 doesn't interact
with well. Is there more information I can provide that would help debug /
troubleshoot?

Thanks!

QH
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