Re: postgresql and smp linux kernel

Thanks for the clear answer.

What about hyper-threading? At the moment, I have
hyper-threading enabled and the OS sees four CPUs (two
physical and two virtual). Do these two virtual ones
really work as the real ones?

I am asking these because we use SAN disks and the
secure-path (a fail safe mechanism) only support UP
kernel. I have to choose do we run smp or do we make
use of secure-path.

Regards
cheng

--- Bill Moran <wmoran(at)potentialtech(dot)com> wrote:
> zhicheng wang <wang_zc(at)yahoo(dot)co(dot)uk> wrote:
>
> > Thanks Oliver Elphick
> > does this mean that the applications do not need
> to be
> > multi-threading in order to use multi-processors?
>
> Yes, that's what it means. Although you've probably
> oversimplified it
> too much. Multi-process applications make use of
> multiple processors
> just as well as multi-threaded apps do.
>
> > --- Oliver Elphick <olly(at)lfix(dot)co(dot)uk> wrote:
> > > On Mon, 2004-08-09 at 11:10, zhicheng wang
> wrote:
> > > > Dear all
> > > >
> > > > i have a dedicated server mainly running
> > > postgresql,
> > > > currently rh-posgtresql-7.3.6.7 (and samba,
> ypbind
> > > > etc). The server is a dual processor machine
> and
> > > the
> > > > OS is RHEL AS 3.
> > > >
> > > > I am currently running
> > > kernel-smp-2.4.21-15.0.4.EL.
> > > >
> > > > My question is: do i need to run smp kernel
> for
> > > > postgresql? What is benefit of it? If I run UP
> > > kernel,
> > > > what do I lose from the point view of PG?
> > >
> > > You do not NEED it for Pg, but it will improve
> > > performance. Each
> > > separate session gets a different process and
> > > therefore has a change to
> > > run on the second processor concurrently with
> > > another session on the
> > > first processor. The same goes for any other
> > > processes that are
> > > running, of course.
> > >
> > > If you do not use an SMP kernel, one of your
> > > processors will sit there
> > > for ever doing nothing, which is money down the
> > > drain.
> > >
> > > --
> > > Oliver Elphick
>
> > > olly(at)lfix(dot)co(dot)uk
> > > Isle of Wight
> > > http://www.lfix.co.uk/oliver
> > > GPG: 1024D/A54310EA 92C8 39E7 280E 3631 3F0E
> 1EC0
> > > 5664 7A2F A543 10EA
> > >
> > > ========================================
> > > "Be still before the LORD and wait
> patiently
> > > for him;
> > > do not fret when men succeed in their
> ways,
> > > when they
> > > carry out their wicked schemes."
> > > Psalms 37:7
> > >
> > >
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> > >
> > > http://www.postgresql.org/docs/faqs/FAQ.html
> > >
> > >
> >
> > =====
> > Best wishes
> > Z C Wang
> >
> >
> >
> >
> >
> >
>
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> Potential Technologies
> http://www.potentialtech.com
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=====
Best wishes
Z C Wang

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