Re: Postgres scalability and performance on windows

Am 23.11.2006 um 23:37 schrieb Gopal:
> hared_buffers = 20000 # min 16 or
> max_connections*2, 8KB each
If this is not a copy & paste error, you should add the "s" at the
beginning of the line.

Also you might want to set this to a higher number. You are setting
about 20000 * 8k = 160MB, this number might be a bit too small if you
do a lot of queries spread over the whole dataset. I don't know
whether the memory management on Windows handles this well, but you
can give it a try.
> effective_cache_size = 82728 # typically 8KB each
Hmm. I don't know what the real effect of this might be as the doc
states:

"This parameter has no effect on the size of shared memory allocated
by PostgreSQL, nor does it reserve kernel disk cache; it is used only
for estimation purposes."

You should try optimizing your shared_buffers to cache more of the data.
> But postgres has everything spread across 10-15 processes, with
> each process using about 10-30MB, not nearly enough to cache all
> the data and ends up doing a lot of disk reads.
It's not soo easy. PostgreSQL maintains a shared_buffer which is
accessible by all processes for reading. On a Unix system you can see
this in the output of top - don't know how this works on Windows.
> In any case I cannot believe that having 15-20 processes running on
> windows helps. Why not spwan of threads instead of processes, which
> migh be far less expensive and more efficient. Is there any way of
> doing this?
Because it brings you a whole lot of other problems? And because
PostgreSQL is not "made for Windows". PostgreSQL runs very good on
Linux, BSD, Mac OS X and others. The Windows version is quite young.

But before you blame stuff on PostgreSQL you should give more
information about the query itself.
> My question is, should I just accept the performance I am getting
> as the limit on windows or should I be looking at some other params
> that I might have missed?
Post the "explain analyse select <your query here>" output here. That
might help to understand, why you get such a high CPU load.

cug