Re: Possible Corrputed shared memory - Mailing list pgsql-novice

Hi James,

Your values seems too low. U allocate 2GB to an application server but only 144M for the DB server. Doesn't it look weird to you?

Perhaps you should consider bumping it up to least 2GB.

Cheers.

On 2 August 2015 at 11:11, James Sebastian <james.sebastian@gmail.com> wrote:

>> [ scratches head... ] It should certainly not have taken very long to
>> replay 10 WAL segments worth of data.  I surmise that the problems
>> you were having before the shutdown were worse than you thought, ie
>> checkpoints were failing to complete, probably due to a persistent
>> I/O error, so that there was a whole lot more than normal to replay
>> after the last successful checkpoint.  Is there any evidence of such
>> distress in the postmaster log?

> We had very slow application performance and many hanging threads as per
> pgadmin -> server status
> Also logs had the following which also indicating probably high I/O (as per
> google search results)

> 2015-07-30 10:10:21 IST WARNING:  pgstat wait timeout
> 2015-07-30 10:12:21 IST WARNING:  pgstat wait timeout

Well, those might mean problems with the stats collector subprocess, but
that's pretty noncritical; it would certainly not have prevented
checkpoints from completing.  No other unexplained log entries?
  

None. I have default  log configuration as given by Ubuntu as default. Probably I would need to increase them to get some more detailed level. I will do some reading on them.

As of now, logging_collector and other log related are commented out, so whatever is default is functioning and logging to postgresql-9.1-main.log

If you have some suggestions, please let me know.

One area of concern, I am realising now which might have contributed to this is below.

I am using postgres as backend db of a java based application over tomcat. JVM is allocated 2048 MB memory heap size from tomcat.
But shared_buffers in postgres was at the default of 32m. I increased them to 144 M and increased shmmax to 320 M. This machine has 8 GB RAM and used as Database and Tomcat/application server.  I can allocate more memory, but my application side colleagues like to know why we keep high and how to figure out instead of blindly allocating a high memory.

I am not even sure how to figure out what should be my buffers.

I now kept
effective_cache_size = 256MB
max_connections = 100
work_mem = 10MB

and all others are default provided by postgres 9.1 in Ubuntu 12.04

Let me know any of them looks bad and worse.

Regards

James

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Regards,
Ang Wei Shan