On 5/21/07, Chris Hoover <[EMAIL PROTECTED]> wrote:
Hi everyone,
I am testing my shared_buffers pool and am running into a problem with slow
inserts and commits. I was reading in several places that in the 8.X
PostgreSQL engines should set the shared_buffers closer to 25% of the
systems memory. On me development system, I have done that. We have 9GB of
memory on the machine and I set my shared_buffers = 292188 (~25% of total
memory).
When my users logged in today, they are noticing the system is much slower.
Tracing my log files, I am seeing that most of the commits are taking over
1sec. I am seeing a range of 1-5 seconds per commit.
What is the correlation here between the shared_buffers and the disk
activity? This is not something I would have expected at all.
have you overcommited your memory? maybe you are thrashing a
bit...long commit times are usually symptom of high iowait. can you
pop up top and monitor iowait for a bit?
can you lower shared buffers again and confirm that performance
increases? how about doing some iostat/vmstat runs and looking for
values that are significantly different depending on the shared
buffers setting.
merlin
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
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