Re: 8.3.9 - latency spikes with Linux (and tuning for consistently low latency)

From: Kevin Grittner
Subject: Re: 8.3.9 - latency spikes with Linux (and tuning for consistently low latency)
Date: ,
Msg-id: 4BC70ADE0200002500030965@gw.wicourts.gov
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In response to: Re: 8.3.9 - latency spikes with Linux (and tuning for consistently low latency)  (Tom Lane)
List: pgsql-performance


Tom Lane <> wrote:

> Have you checked whether the spikes correlate with checkpoints?
> Turn on log_checkpoints and watch for awhile.  If so, fooling with
> the checkpoint parameters might give some relief.

If that by itself doesn't do it, I've found that making the
background writer more aggressive can help.  We've had good luck
with:

bgwriter_lru_maxpages = 1000
bgwriter_lru_multiplier = 4.0

If you still have checkpoint-related latency issues, you could try
scaling back shared_buffers, letting the OS cache handle more of the
data.

Also, if you have a RAID controller with a battery-backed RAM cache,
make sure it is configured for write-back.

-Kevin


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