Memory afinity - Suse

This is a discussion on Memory afinity - Suse ; I had an application vendor tell me that I could set memory affinity for a processor. In other words if I had 8GB of memory in a two processor box I could set 4 GB per processor or 6 to ...

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Thread: Memory afinity

  1. Memory afinity

    I had an application vendor tell me that I could set memory affinity for a
    processor. In other words if I had 8GB of memory in a two processor box I
    could set 4 GB per processor or 6 to one processor and 2 to the other
    instead of all 8 being availble to which ever processor needed it. Is this
    true and if so how do I set it?

    Andrew




  2. Re: Memory afinity

    On Wed, 10 Oct 2007 16:41:54 +0000, Andrew Madsen wrote:

    > I had an application vendor tell me that I could set memory affinity for a
    > processor. In other words if I had 8GB of memory in a two processor box I
    > could set 4 GB per processor or 6 to one processor and 2 to the other
    > instead of all 8 being availble to which ever processor needed it. Is this
    > true and if so how do I set it?


    The important question to ask before that one is, can you do more efficient
    memory allocation than the kernel can?

  3. Re: Memory afinity


    "Mark South" wrote in message
    news:470d016c$1_2@news.bluewin.ch...
    > On Wed, 10 Oct 2007 16:41:54 +0000, Andrew Madsen wrote:
    >
    >> I had an application vendor tell me that I could set memory affinity for
    >> a
    >> processor. In other words if I had 8GB of memory in a two processor box I
    >> could set 4 GB per processor or 6 to one processor and 2 to the other
    >> instead of all 8 being availble to which ever processor needed it. Is
    >> this
    >> true and if so how do I set it?

    >
    > The important question to ask before that one is, can you do more
    > efficient
    > memory allocation than the kernel can?


    I do not believe I can but the vendor seemed to indicate that he kernel
    cannot do a good job so you need to set the memory affinity to allocate the
    memory better. This is an analytical program and they were saying that one
    scenario would be to have 8GB and assign 6GB to one processor where the
    analytical application would run and the remaining 2GB to the other
    processor so the rest of the box could run.



  4. Re: Memory afinity

    On Wed, 10 Oct 2007 17:20:42 +0000, Andrew Madsen wrote:

    > "Mark South" wrote in message
    > news:470d016c$1_2@news.bluewin.ch...
    >> On Wed, 10 Oct 2007 16:41:54 +0000, Andrew Madsen wrote:
    >>
    >>> I had an application vendor tell me that I could set memory affinity for
    >>> a
    >>> processor. In other words if I had 8GB of memory in a two processor box I
    >>> could set 4 GB per processor or 6 to one processor and 2 to the other
    >>> instead of all 8 being availble to which ever processor needed it. Is
    >>> this
    >>> true and if so how do I set it?

    >>
    >> The important question to ask before that one is, can you do more
    >> efficient
    >> memory allocation than the kernel can?

    >
    > I do not believe I can but the vendor seemed to indicate that he kernel
    > cannot do a good job so you need to set the memory affinity to allocate the
    > memory better. This is an analytical program and they were saying that one
    > scenario would be to have 8GB and assign 6GB to one processor where the
    > analytical application would run and the remaining 2GB to the other
    > processor so the rest of the box could run.


    Then you should try it both ways and let us know how the performance
    compares.

    I'll bet all my spam mail for one entire month that the kernel has a
    better clue :-)

  5. Re: Memory afinity


    "Mark South" wrote in message
    news:470d48bb$1_2@news.bluewin.ch...
    > On Wed, 10 Oct 2007 17:20:42 +0000, Andrew Madsen wrote:
    >
    >> "Mark South" wrote in message
    >> news:470d016c$1_2@news.bluewin.ch...
    >>> On Wed, 10 Oct 2007 16:41:54 +0000, Andrew Madsen wrote:
    >>>
    >>>> I had an application vendor tell me that I could set memory affinity
    >>>> for
    >>>> a
    >>>> processor. In other words if I had 8GB of memory in a two processor box
    >>>> I
    >>>> could set 4 GB per processor or 6 to one processor and 2 to the other
    >>>> instead of all 8 being availble to which ever processor needed it. Is
    >>>> this
    >>>> true and if so how do I set it?
    >>>
    >>> The important question to ask before that one is, can you do more
    >>> efficient
    >>> memory allocation than the kernel can?

    >>
    >> I do not believe I can but the vendor seemed to indicate that he kernel
    >> cannot do a good job so you need to set the memory affinity to allocate
    >> the
    >> memory better. This is an analytical program and they were saying that
    >> one
    >> scenario would be to have 8GB and assign 6GB to one processor where the
    >> analytical application would run and the remaining 2GB to the other
    >> processor so the rest of the box could run.

    >
    > Then you should try it both ways and let us know how the performance
    > compares.
    >
    > I'll bet all my spam mail for one entire month that the kernel has a
    > better clue :-)


    But in order to try it I need to be able to configure affinity and THAT was
    the reason for the thread. Does anyone know how to assign memory so that a
    portion of it is used exclusively by a particular processor?



  6. Re: Memory afinity

    Andrew Madsen wrote:
    > But in order to try it I need to be able to configure affinity and THAT was
    > the reason for the thread. Does anyone know how to assign memory so that a
    > portion of it is used exclusively by a particular processor?


    Memory is assigned to processes, not processors. "Memory affinity" would hence
    require a set "processor affinity" for a process. It's nonsense to think about
    unless you have machine partitioning in mind, S/390 style.

    kind regards,
    Andreas

  7. Re: Memory afinity


    "Andreas" wrote in message
    news:470e230f$1@news.uni-ulm.de...
    > Andrew Madsen wrote:
    >> But in order to try it I need to be able to configure affinity and THAT
    >> was
    >> the reason for the thread. Does anyone know how to assign memory so that
    >> a
    >> portion of it is used exclusively by a particular processor?

    >
    > Memory is assigned to processes, not processors. "Memory affinity" would
    > hence
    > require a set "processor affinity" for a process. It's nonsense to think
    > about
    > unless you have machine partitioning in mind, S/390 style.
    >
    > kind regards,
    > Andreas


    In all the systems I have come across this is the case. Creating an LPAR is
    independent of the OS. I was thinking that the vendor and I were not
    comptemplating the same thing but I had to check to see if I was wrong.
    Since this would be a process within an LPAR then I am gathering that I
    cannot assign memory to a processor just an application. So to recap - I
    cannot take 6GB of 8GB and assign it to processor 0. If it is running a
    process that requires that much memory then it will take it.



  8. Re: Memory afinity

    On Thu, 11 Oct 2007 13:12:47 +0000, Andrew Madsen wrote:

    >>> scenario would be to have 8GB and assign 6GB to one processor where the
    >>> analytical application would run and the remaining 2GB to the other
    >>> processor so the rest of the box could run.

    >>
    >> Then you should try it both ways and let us know how the performance
    >> compares.
    >>
    >> I'll bet all my spam mail for one entire month that the kernel has a
    >> better clue

    >
    > But in order to try it I need to be able to configure affinity and THAT was
    > the reason for the thread. Does anyone know how to assign memory so that a
    > portion of it is used exclusively by a particular processor?


    Well, this is a Linux group and that seems to be a hardware question.
    Maybe a hardware group could give you an answer?

    You'll just have to forgive me for having tried to persuade you not to
    waste your time....

  9. Re: Memory afinity


    "Mark South" wrote in message
    news:470e4ca6$1_3@news.bluewin.ch...
    > On Thu, 11 Oct 2007 13:12:47 +0000, Andrew Madsen wrote:
    >
    >>>> scenario would be to have 8GB and assign 6GB to one processor where the
    >>>> analytical application would run and the remaining 2GB to the other
    >>>> processor so the rest of the box could run.
    >>>
    >>> Then you should try it both ways and let us know how the performance
    >>> compares.
    >>>
    >>> I'll bet all my spam mail for one entire month that the kernel has a
    >>> better clue

    >>
    >> But in order to try it I need to be able to configure affinity and THAT
    >> was
    >> the reason for the thread. Does anyone know how to assign memory so that
    >> a
    >> portion of it is used exclusively by a particular processor?

    >
    > Well, this is a Linux group and that seems to be a hardware question.
    > Maybe a hardware group could give you an answer?
    >
    > You'll just have to forgive me for having tried to persuade you not to
    > waste your time....


    Believe me I do not feel I have wasted my time. This would be OS only
    related because the hardware does not have that capability I have ever seen.
    Basically I was interested in finding out if the vendor was blowing smoke in
    areas that it shouldn't be and I believe that answer is yes he was blowing.
    Thank you for your help.



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