Re: again on index usage - Mailing list pgsql-hackers

From Daniel Kalchev
Subject Re: again on index usage
Date
Msg-id 200201101609.SAA03944@dcave.digsys.bg
Whole thread Raw
In response to Re: again on index usage  ("Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at>)
List pgsql-hackers
>>>"Zeugswetter Andreas SB SD" said:> > > [with the new effective_cache_size = 6400]> > This seems way too low for a
512Mb machine. Why does your OS> only use so little for filecache ? Is the rest used for processes ?> For the above
numberyou need to consider OS cache and shared_buffers.> You can approximatly add them together minus a few %.
 

As far as I am aware, 10% for buffer space is the default for BSD operating 
systems... although I have seen buffer space = 50% on MacOS X. There is no 
problem to increase the buffer space in kernel, although I am not very 
confident this will give much better overall performance (well, more memory 
can be added as well).
> With the data you gave, a calculated value for effective_cache_size> would be 29370, assuming the random_page_cost is
actually4 on your> machine. 29370 might be a slight overestimate, since your new table> will probably still be somewhat
sortedby date within one IP.
 

random_page_cost is 4.

If the select into then cluster do this, then yes, it is possible, but not 
guaranteed.

I will try with increased effective_cache_size.

Postmaster is started with -N 128 -B 256 -i -o "-e -S 10240" 

Daniel



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