IDS Forum

Re: Multiprocessor setting

Posted By: Art Kagel
Date: Thursday, 22 July 2010, at 3:56 p.m.

In Response To: RE: Multiprocessor setting (Wyza, Jonathon)

John's talking about OS scheduling. With your applications and a web server
all sharing the same set of processors, I'm not surprised that the VP
efficiency is around 35%. If most application and web server tasks entail
accessing the database then any action requires at least two processes to
dig in and start burning CPU cycles.

However, efficiency or 35% in this case doesn't necessarily mean that if you
separate the apps and web server to separate machines that things will
happen 65% faster. It does mean, though, that as your load increases
running IDS, apache, and applications on three dedicated boxes instead of
sharing just one will allow you to handle three times the load. But that's
not any surprise, is it?

Part of John's point, IB, is that the CPU VPs are spinning waiting for
latches to be released so that they are less likely to be put to sleep by
the OS than if they blocked on the latches. That means that Informix may
actually have more than 3x capacity available even though the CPU efficiency
shows only that much. On a smaller shared box, with only two CPU cores,
this spinning can prevent applications from getting enough processor time
and it can be better to set MULTIPROCESSOR to zero to eliminate the spinning
and release the processors for non-database work.

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 3:12 PM, Wyza, Jonathon <wyzaj@bethelcollege.edu>wrote:

> Hmm, that is very interesting. If possible, I'd love some insight on this
> then: (keep in mind this data is only for 2 days as our server had to be
> bounced)
>
> Individual virtual processors:
> vp pid class usercpu syscpu total Thread Eff
> 1 5641 cpu 3081.92 465.82 3547.74 10262.72 34%
> 3 5654 cpu 2383.56 375.91 2759.47 8820.97 31%
> 4 5655 cpu 1536.83 265.24 1802.07 4115.01 43%
> 5 5656 cpu 523.68 57.73 581.41 2616.73 22%
> 6 5657 cpu 212.99 24.26 237.25 860.44 27%
> 7 5658 cpu 148.73 15.23 163.96 466.68 35%
> 8 5659 cpu 117.42 9.84 127.26 289.41 43%
>
> When you say scheduling, do you mean IDS scheduling or system/application
> scheduling?
>
> >From onconf
> MULTIPROCESSOR 1
> VPCLASS cpu,num=7,noage
>
> These processors are shared with apache, and our application.
>
> Jonathon Wyza
> CX & CBORD System Administrator
> CX Programmer/Analyst
> Administrative Computing
> Bethel College
> (574)-257-3381
> AIM: Iamwyza
> jonathon.wyza@bethelcollege.edu
> ==============================
> SLES 11x64 & IDS 11.50.FC6
>
> "Don't document the problem, fix it."
> - Atli Björgvin Oddsson
>
> -----Original Message-----
> From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of John
> Miller iii
> Sent: Thursday, July 22, 2010 3:00 PM
> To: ids@iiug.org
> Subject: Re: Multiprocessor setting [20630]
>
> 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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> > > --0016e6d26c9a46bc9c048bfcd63e
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> > >
> > >
> >
>
> ****************************************************************************
>
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> > >
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--00163628532a10419f048bff4e9b

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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