From: | Alfred Perlstein <bright(at)wintelcom(dot)net> |
---|---|
To: | Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Need help with phys backed shm segments (Postgresql+FreeBSD). |
Date: | 2000-12-05 22:52:33 |
Message-ID: | 20001205145233.I8051@fw.wintelcom.net |
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Lists: | pgsql-hackers |
* Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> [001205 13:33] wrote:
> Alfred,
>
> do you have any numbers with and without your patch ?
> I mean performance. You may use pg_check utility.
Er, I just made the patch a couple of hours ago, and I'm also
dealing with some other FreeBSD issues right now. I will report
on it as soon as I can.
Theoretically You'll only see performance gains when doing fork(),
the real intent here is to allow for giant segments, without
kern.ipc.shm_use_phys=1 running let's say 768meg (out of 1gig)
shared memory segments will probably cause performance problems
because of the amount of swap structures needed per-process to
manage swappable segments.
I'm going to be enabling this on one of our boxes and see if it
makes a noticeable difference. I'll let you guys know.
> > Date: Tue, 5 Dec 2000 13:04:45 -0800
> > From: Alfred Perlstein <bright(at)wintelcom(dot)net>
> > To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
> > Cc: pgsql-hackers(at)postgresql(dot)org
> > Subject: Re: [HACKERS] Need help with phys backed shm segments (Postgresql+FreeBSD).
> >
> > Here's the patch I'm using on FreeBSD, it seems to work, if any
> > other FreeBSD'ers want to try it out, just apply the patch:
> > cd /usr/src/sys/vm ; patch < patchfile
> >
> > and recompile and boot with a new kernel, then do this:
> >
> > sysctl -w kern.ipc.shm_use_phys=1
> >
> > or add:
> > kern.ipc.shm_use_phys=1
> > to /etc/sysctl.conf
> >
> > Let me know if it works.
> >
> > thanks,
> > -Alfred
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