Re: [PERFORM] FW: Tx forecast improving harware capabilities.

2005-08-18 Thread David Hodgkinson


On 18 Aug 2005, at 16:01, Sebastian Lallana wrote:


It exists something like this? Does anybody has experience about  
this subject?


I've just been through this with a client with both a badly tuned Pg and
an application being less than optimal.

First, find a benchmark. Just something you can hold on to. For us, it
was the generation time of the site's home page. In this case, 7  
seconds.

We looked hard at postgresql.conf, planned the memory usage, sort_memory
and all that. That was a boost. Then we looked at the queries that were
being thrown at the database. Over 200 to build one page! So, a layer
of caching was built into the web server layer. Finally, some frequently
occurring combinations of queries were pushed down into stored procs.
We got the page gen time down to 1.5 seconds AND the server being stable
under extreme stress. So, a fair win.

Thanks to cms for several clues.

So, without understanding your application and were it's taking the  
time,

you can't begin to estimate hardware usage.



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Re: [PERFORM] context-switching issue on Xeon

2005-07-19 Thread David Hodgkinson


FWIW, I'm seeing this with a client at the moment. 40-60k CS per second
on Dual 3.2GHz.

There are plenty of other issues we're dealing with, but this is  
obviously

disconcerting...


On 19 Jul 2005, at 19:23, Sailer, Denis (YBUSA-CDR) wrote:

The thread below has the test case that we were able to use to  
reproduce the issue.



http://archives.postgresql.org/pgsql-performance/2004-04/msg00280.php


The last messages on this subject are from April of 2005.  Has  
there been any successful ways to significantly reduce the impact  
this has to multi-processing?  I haven’t been able to find anything  
showing a resolution of some kind.



We are seeing this on two of our machines:


Quad 3.0 GHz XEON with 3GB of memory running PG 7.4.3 with SuSE  
kernel 2.4



Dual 2.8 GHz XEON with 2GB of memory running PG 8.0.0 with SuSE  
kernel 2.4









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