I guess the thing to do is to move this topic over to a freebsd list where we can get more definitive answers on how disk caching is handled. I asked here since I know that FreeBsd is often recommended, http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html# as a good platform for postgres, and with Modern machines often having Gigabytes of memory the issue of, possibly, having a disk cache of 200MB would be one often asked.
On Fri, Feb 27, 2004 at 12:46:08PM +0530, Shridhar Daithankar wrote: > Dror Matalon wrote: > > >Let me try and say it again. I know that setting effective_cache_size > >doesn't affect the OS' cache. I know it just gives Postgres the *idea* > >of how much cache the OS is using. I know that. I also know that a > >correct hint helps performance. > > > >I've read Matt Dillon's discussion about the freebsd VM at > >http://www.daemonnews.org/200001/freebsd_vm.html and I didn't see him > >saying that Freebsd uses all the free RAM for disk cache. Would you care > >to provide a URL pointing to that? > > I don't believe freeBSD yses everything available unlike linux. It is > actually a good thing. If you have 1GB RAM and kernel buffers set at 600MB, > you are guaranteed to have some mmory in crunch situations. > > As far you original questions, I think you can increase the kernel buffer > sizes for VFS safely. However remembet that more to dedicate to kernel > buffers, less space you have in case of crunch for whatever reasons. > > FreeBSD gives you a control which linux does not. Use it to best of your > advantage.. > > Shridhar -- Dror Matalon Zapatec Inc 1700 MLK Way Berkeley, CA 94709 http://www.fastbuzz.com http://www.zapatec.com ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html