Re: Would my postgresql 8.4.12 profit from doubling RAM?

On Sat, Sep 29, 2012 at 2:21 PM, Alexander Farber
<alexander(dot)farber(at)gmail(dot)com> wrote:
> Hello Scott and others,
>
> On Sat, Sep 29, 2012 at 9:38 PM, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> wrote:
>> On Sat, Sep 29, 2012 at 11:27 AM, Alexander Farber
>> <alexander(dot)farber(at)gmail(dot)com> wrote:
>>> I've finally doubled up RAM to 32 GB for my Quad core
>>> CentOS 6.3 server and have changed postgresql.conf to
>>>
>>> max_connections = 100
>>> shared_buffers = 4096MB
>>> work_mem = 16M
>>>
>>> http://serverfault.com/questions/433281/doubled-up-ram-to-32-gb-now-how-to-speed-up-a-lapp-server
>>
>> I'd suggest turning on persistent connections because you DO use
>> pgbouncer. It'll reduce connection time and give slightly better
>> performance. But from reading that page, I don't think you've given
>> us (or yourself really) enough data to tell you how to improve
>> performance.
>>
>> The first thing to do is some simple performance profiling in your php
>> script. Just add error_log() or whatever it's called in php, with
>> some timing info in them to see where your time is being spent. If
>> it's mostly on the db side, we head there, if it's mostly in the php
>> we look there. At first just put in a couple statements throughout
>> your script (include things like pid etc so you can trawl your logs
>> for this later) to get an idea where in general you're spending your
>> time. Once we get a handle on where most of it is going we'll go from
>> there.
>
> actually that's what I tried yesterday,
> right after the server was upgraded -
>
> I've set in postgresql.conf
>
> max_connections = 600
>
> (to match the 500 MaxClients in httpd.conf)
> and then in /etc/php.ini

Whoa aren't you running pg bouncer? If so then leave pg alone, adjust
pg bouncer. Revert that db side change, examine pgbouncer config etc.

> pgsql.allow_persistent = On
>
> and added the ..., array(PDO::ATTR_PERSISTENT => true);
> to my PHP scripts -
>
> and suddenly my scripts stopped fetching any
> data from the database, were only returning empty values...
>
> I have to retry this with d/b logs on...

After fixing above mentioned change.

> About not giving enough information -
> how much information do you want?
> If I list all my databases + source code
> of the scripts, I doubt anyone will read my mail.

Re-read my previous post about profiling.