Re: Dual Xeon + HW RAID question

From: Bruce Momjian
Subject: Re: Dual Xeon + HW RAID question
Date: ,
Msg-id: 200307221738.h6MHcBF03404@candle.pha.pa.us
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In response to: Re: Dual Xeon + HW RAID question  (SZUCS Gábor)
List: pgsql-performance

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Dual Xeon + HW RAID question  ("alexandre arruda paes :: aldeia digital", )
 Re: Dual Xeon + HW RAID question  (Rod Taylor, )
 Re: Dual Xeon + HW RAID question  ("Nikolaus Dilger", )
  [OT] Such incredible h/w (was Re: Dual Xeon + HW RAID question)  (Ron Johnson, )
  Re: Dual Xeon + HW RAID question  (Andrew Sullivan, )
  Re: Dual Xeon + HW RAID question  (SZUCS Gábor, )
   Re: Dual Xeon + HW RAID question  ("alexandre paes :: aldeia digital", )
   Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
    Re: Dual Xeon + HW RAID question  ("Mindaugas Riauba", )
     Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
      Re: Dual Xeon + HW RAID question  (SZUCS Gábor, )
       Re: Dual Xeon + HW RAID question  (Jord Tanner, )
        Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
         Re: Dual Xeon + HW RAID question  (Jord Tanner, )
          Re: Dual Xeon + HW RAID question  (Bruce Momjian, )
           Re: Dual Xeon + HW RAID question  (Jord Tanner, )
       Re: Dual Xeon + HW RAID question  (Bruce Momjian, )

SZUCS G�bor wrote:
> "by default" -- do you mean there is a way to tell Linux to favor the second
> real cpu over the HT one? how?

Right now there is no way the kernel can tell which virtual cpu's are on
each physical cpu's, and that is the problem.  Once there is a way,
hyperthreading will be more useful, but even then, it doesn't double
your CPU throughput, just increases by 40%.


> > Right, I simplified it.  The big deal is whether the OS favors the
> > second real CPU over one of the virtual CPU's on the same die --- by
> > default, it doesn't.  Ever if it did work perfectly, you are talking
> > about going from 1 to 1.4 or 2 to 2.8, which doesn't seem like much.
>
>
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