IDS Forum

Re: Multiprocessor setting

Posted By: Fernando Nunes
Date: Thursday, 22 July 2010, at 6:27 p.m.

In Response To: Re: Multiprocessor setting (John Miller iii)

One side note:
There was a bug with the efficiency metric IF you run onstat -z.
Some counters were not reset and the calculation of Efficiency became 0
(with time)
It's fixed in 11.50.xC6.
Systems where onstat -z is not run should not be affected.

Reference: idsdb00189503

Regards.

On Thu, Jul 22, 2010 at 8:00 PM, John Miller iii <miller3@us.ibm.com> wrote:

> Just a few comments:
>
> 1. The MULTIPROCESSOR onconfig parameter does not have to do with "IF"
>
> synchronization to shared memory is done, but rather the type of
> latch
>
> which is done. If you turn on MULTIPROCESSOR onconfig paramater
>
> all you latching calls will spin. This is often faster when you are
> not short
>
> on cpu cylces. You can see this spinning in an onstat -g spi. (lots
> of output).
>
> 2. Yes when I was talking in my old presentations about processors this
> was really
>
> prior to cores. So no you should take this to mean cores, not
> processors.
>
> The reason why it might be faster to have MULTIPROCESSOR off in a
> two
>
> core system is if you are running application and other work, the
> lack of busy
>
> spinning can provided time for other operations to run.
>
> 3. As for the number of cpu vps exceeding the number of physical cores
> (see comments
>
> about processor threads below). I generally find this is only an
> advantage when
>
> other things are not tuned correctly. We have added a new metric
> which has
>
> simplified this greatly. This new metric is included now in onstat
> -g glo. It is the Efficiency
>
> column for the CPU vps. This tells informix how well the operating
> system is
>
> scheduling the oninit processes.
>
> What is the Eff (or Efficiency) column. It compare the amount of
> time the
>
> Hardware core has given the oninit process to run VERSUS the amount
> of time
>
> Informix threads have been running. The efficiency is made into a
> percentage.
>
> Individual virtual processors:
> vp pid class usercpu syscpu total Thread Eff
> 1 1452 cpu 997.25 25.06 1022.31 1103.17 92%
>
> total = 1022.31 - time the hardware core has give oninit cpu vp to
> run
>
> Thread = 1103.17 - time Informix had threads running
>
> Approx 92% of the time oninit is running when it has work, and only
> 8% of the
>
> time it is not running when it has work. This is a very good
> number.
>
> I have been on system where they barely make 40% efficiency. This mean the
> oninit process is getting less than half of the time on the hardware
> processor. If
> this is the case you really need to check the scheduling, noage, and what
> else
> is this processor doing.
>
> 4. Processor threads.
> These generally do not help as much as cores. While implementation of
> these vary
> widely by hardware vendor. You need to know that these where created to
> consume
> the idle time or stalls by hardware core. While database designers
> generally do try
> to mitigate these already with many performance tricks, you will receive
> benefits
> from them processor threads, but not near as much as cores.
>
> John F. Miller III
> STSM, Support Architect
> miller3@us.ibm.com
> 503-578-5645
> IBM Informix Dynamic Server (IDS)
>
> ids-bounces@iiug.org wrote on 07/22/2010 10:46:55 AM:
>
> > [image removed]
> >
> > Re: Multiprocessor setting [20624]
> >
> > Art Kagel
> >
> > to:
> >
> > ids
> >
> > 07/22/2010 10:47 AM
> >
> > Sent by:
> >
> > ids-bounces@iiug.org
> >
> > Please respond to ids
> >
> > Yeah, Intels were always deficient in multiprocessing compared to the
> other
> > processors out there. For example, while I've recommended that you can
> > treat each 500MHZ of processor speed as an additional CPU VP on most
> > processors, I use about 750-800MHZ on Intel processors.
> >
> > I find the AMD x86 offerings do better at this.
> >
> > Art
> >
> > Art S. Kagel
> > Advanced DataTools (www.advancedatatools.com)
> > IIUG Board of Directors (art@iiug.org)
> >
> > Disclaimer: Please keep in mind that my own opinions are my own opinions
> and
> > do not reflect on my employer, Advanced DataTools, the IIUG, nor any
> other
> > organization with which I am associated either explicitly, implicitly, or
> by
> > inference. Neither do those opinions reflect those of other individuals
> > affiliated with any entity with which I am affiliated nor those of the
> > entities themselves.
> >
> > On Thu, Jul 22, 2010 at 1:06 PM, Paul Watson <paul@oninit.com> wrote:
> >
> > > I'd also add that we used to be able run NUMCPUVPS > physical CPUs and
> see
> > > a
> > > performance increase. I'm not seeing that at all with the Intel
> multicores
> > >
> > > Cheers
> > > Paul
> > >
> > > -----Original Message-----
> > > From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
> Art
> > > Kagel
> > > Sent: Thursday, July 22, 2010 11:59 AM
> > > To: ids@iiug.org
> > > Subject: Re: Multiprocessor setting [20619]
> > >
> > > I think that a quad core processor qualifies as a 3 CPU system. Atthe
> time
> > > that John said that, #cores == #processors. Since that's no longer
> true, I
> > > would go with the number of cores rather than the number of processors.
>
> > >
> > > That said, I was always told that if you have more than one core you
> need
> > > to
> > > set MULTIPROCESSOR to 1 to add additional locking/latching of memory to
>
> > > prevent simultaneous access to memory structures by more than one CPU
> VP.
> > > John?
> > >
> > > Art
> > >
> > > Art S. Kagel
> > > Advanced DataTools (www.advancedatatools.com)
> > > IIUG Board of Directors (art@iiug.org)
> > >
> > > Disclaimer: Please keep in mind that my own opinions are my own
> opinions
> > > and
> > > do not reflect on my employer, Advanced DataTools, the IIUG, nor any
> other
> > > organization with which I am associated either explicitly, implicitly,
> or
> > > by
> > > inference. Neither do those opinions reflect those of other individuals
>
> > > affiliated with any entity with which I am affiliated nor those of the
> > > entities themselves.
> > >
> > > On Thu, Jul 22, 2010 at 10:59 AM, kate <kate@iiug.org> wrote:
> > >
> > > > Hey Gurus,
> > > > A few years back in a performance presentation from John Miller, he
> > > > discussed the correct tuning for 2 CPU systems. He mentioned that the
>
> > > > MULTIPROCESSOR in the config file should actually be set to 0 (off)
> for
> > > two
> > > > CPU systems to stop the engine from doing unnessary spinning waiting
> for
> > > > the
> > > > next processor. He said that this value only improved the performance
> of
> > > a
> > > > 3 CPU system or more.
> > > >
> > > > My question is - is that still true for version 11.5 and todays new
> quad
> > > > core CPUs?
> > > >
> > > > Thanks!
> > > > Kate Tomchik [ kate@iiug.org ] www.iiug.org
> > > > International Informix Users Group Board of Directors
> > > >
> > > > A computer lets you make more mistakes faster than any inventionin
> human
> > > > history - with the possible exceptions of handguns and tequila.
> > > > Mitch Ratliffe
> > > >
> > > >
> > > >
> > > >
> > >
> > >
> >
>
> ****************************************************************************
>
> > > ***
> > > > Forum Note: Use "Reply" to post a response in the discussion forum.
> > > >
> > > >
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> > >
> > >
> >
>
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>
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> > >
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>

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

--0016e6ddab47539949048c016c9e

Messages In This Thread

• Multiprocessor setting
  kate -- Thursday, 22 July 2010, at 10:59 a.m.
  • Re: Multiprocessor setting
    Obnoxio The Clown -- Thursday, 22 July 2010, at 11:01 a.m.
    • Re: Multiprocessor setting
      Fernando Nunes -- Thursday, 22 July 2010, at 11:07 a.m.
    • Re: Multiprocessor setting
      Alexandre Marini -- Thursday, 22 July 2010, at 11:15 a.m.
  • RE: Multiprocessor setting
    Wyza, Jonathon -- Thursday, 22 July 2010, at 11:06 a.m.
  • Re: Multiprocessor setting
    Art Kagel -- Thursday, 22 July 2010, at 12:59 p.m.
    • Re: Multiprocessor setting
      Fernando Nunes -- Thursday, 22 July 2010, at 1:03 p.m.
    • RE: Multiprocessor setting
      Paul Watson -- Thursday, 22 July 2010, at 1:06 p.m.
      • RE: Multiprocessor setting
        Wyza, Jonathon -- Thursday, 22 July 2010, at 1:12 p.m.
        • Re: Multiprocessor setting
          Art Kagel -- Thursday, 22 July 2010, at 1:41 p.m.
          • Re: Multiprocessor setting
            Lester Knutsen -- Thursday, 22 July 2010, at 2:11 p.m.
            • Re: Multiprocessor setting
              Art Kagel -- Thursday, 22 July 2010, at 2:35 p.m.
      • Re: Multiprocessor setting
        Art Kagel -- Thursday, 22 July 2010, at 1:46 p.m.
        • Re: Multiprocessor setting
          John Miller iii -- Thursday, 22 July 2010, at 3:00 p.m.
          • RE: Multiprocessor setting
            Wyza, Jonathon -- Thursday, 22 July 2010, at 3:12 p.m.
            • Re: Multiprocessor setting
              Art Kagel -- Thursday, 22 July 2010, at 3:56 p.m.
            • Re: Multiprocessor setting
              Alexandre Marini -- Thursday, 22 July 2010, at 3:57 p.m.
          • Re: Multiprocessor setting
            Fernando Nunes -- Thursday, 22 July 2010, at 6:27 p.m.
  • Re: Multiprocessor setting
    Richard Snoke -- Thursday, 22 July 2010, at 2:12 p.m.
    • Re: Multiprocessor setting
      Art Kagel -- Thursday, 22 July 2010, at 2:46 p.m.
      • Re: Multiprocessor setting
        Richard Snoke -- Thursday, 22 July 2010, at 3:12 p.m.

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