On 11 Dec 2002 at 17:53, Fred Moyer wrote:
> I have noticed that increasing the shared buffers has always had a
> positive performance effect on my system. I'm not saying it will help
> everyone but check out the attached (simple) benchmarks I ran. The
> results have been repeatable.
>
> I always use as many shared buffers as I can but right now I can't been
> able to go above 2 GB worth until I reconfigure the kernel to take more
> than 2 GB shared memory. Right now /proc/sys/kernel/shmmax is at
> 2192000000. Note that for some reason I was able to configure 2 GB shared
> memory on a machine with 1.5 GB ram (was testing against my production
> server which has 4 GB). Not sure why that is but definitely try this
> yourself.
I believe even if you push kernel memory to past 2GB, you can not make
postgresql use it, because IIRC Tom said, all shared buffers count were int and
can not go past beyong 250K on 32 bit machines.
Possibly recompiling postgresql with a long long shared count and/or bigger
page size might make a difference.
Personally I would recompile postgresql with 16KB as page size if database size
is past a gig. It should avoid some fragmentation. I don't have any results to
say that it will work better but I believe it is worth an experiement. Anything
more than that might be overkill.
Bye
Shridhar
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