Re: memory strangeness (fwd) - Mailing list pgsql-admin
From | Curt Sampson |
---|---|
Subject | Re: memory strangeness (fwd) |
Date | |
Msg-id | Pine.NEB.4.44.0207051104460.478-100000@angelic.cynic.net Whole thread Raw |
In response to | memory strangeness (fwd) (Gregor Mosheh <stigmata@blackangel.net>) |
Responses |
Re: memory strangeness (fwd)
(Tom Lane <tgl@sss.pgh.pa.us>)
Re: memory strangeness (fwd) (Gregor Mosheh <stigmata@blackangel.net>) |
List | pgsql-admin |
On Thu, 4 Jul 2002, Gregor Mosheh wrote: > Hiya. I've installed Postgres 7.2 on a dedicated FreeBSD system with 384 > MB RAM. Because the system will be doing nothing except PG, I'd like to > dump as much memory as possible into PG's shared memory. Well, see Tom's comments on this, 'cause that's what I always say too. (I'm a NetBSD developer, but FreeBSD's internals aren't so different, really.) However, if you wanted to do it both ways, and benchmark your application, I'd be really interested in hearing about the results. > I rebuilt the kernel with very large limits: 330 MB on the MAXDSIZ and > DFLDSIZ, and 330 MB for SHMMAXPAGES. This gives me: You don't need to rebuild for DFLDSIZ; you can always bump that up to MAXDSIZ with sysctl (assuming you're root--do it before you "su pgsql -c nadanada" in your startup script). And moving MAXDSIZ to 330 MB looks like a reduction to me; FreeBSD's default in 4.6-RELEASE is 512 MB. (NetBSD's is 1GB.) You probably want to check /usr/include/machine/vmparam.h for default settings before changing stuff like this, lest you accidently lower it instead. > I still cannot set PG's shared_buffers higher than 20000 (160 MB): Shared memory pages, IIRC, are locked, meaning that they cannot be swapped. There's always a limit on the number of locked pages you may have in the system in total, if only becuase the system has only so much physical RAM. But for some reasont he RLIMIT_MEMLOCK parameter on my nearest FreeBSD 4.6 system is a bit bogus: server2 $ ulimit -Ha | grep locked lockedmem(kbytes) unlimited (I certainly cannot lock an unlimited number of pages in this 1GB machine! And for some reason it's also saying that my RLIMIT_RSS is unlimited; again, this should return no more than the physical RAM available in the machine.) So I suspect you're running into some other, more secret, limit on the number of pages that the system or a process may lock into RAM. So you'll want to dig around the kernel to find out where this is, and tweak it. cjs -- Curt Sampson <cjs@cynic.net> +81 90 7737 2974 http://www.netbsd.org Don't you know, in this new Dark Age, we're all light. --XTC
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