Re: [PATCH 00/07][RFC] i386: NUMA emulation

From: Magnus Damm (magnus.damm_at_gmail.com)
Date: 10/03/05

  • Next message: Rogério Brito: "Re: Strange disk corruption with Linux >= 2.6.13" 
    Date:	Mon, 3 Oct 2005 14:05:34 +0900
To: Paul Jackson <pj@sgi.com>

    On 10/3/05, Paul Jackson <pj@sgi.com> wrote:
    > Dave wrote:
    > > Also, I worry that simply #ifdef'ing things out like CPUsets' update
    > > means that CPUsets lacks some kind of abstraction that it should have
    > > been using in the first place.
    >
    > In the abstract, cpusets should just assume that the system has one or
    > more CPUs, and one or more Memory Nodes. Ideally, it should not
    > require either SMP nor NUMA. Indeed, if you (Magnus) can get it
    > to compile with just one or the other of those two:
    >
    > config CPUSETS
    > bool "Cpuset support"
    > - depends on SMP
    > + depends on SMP || NUMA
    >
    > then I would hope that it would compile with neither. The cpuset
    > hierarchy on such a system would be rather boring, with all cpusets
    > having the same one CPU and one Memory Node, but it should work ... in
    > theory of course.

    I just tested this on top of my patches:
    @@ -245,7 +245,6 @@ config IKCONFIG_PROC

     config CPUSETS
            bool "Cpuset support"
    - depends on SMP || NUMA
            help

    and it seems to work ok in practice too. On a regular !SMP !NUMA PC
    anyway. As you note, the hierarchy is not that exciting. =) Anyway,
    both SMP || NUMA or nothing seems to work as dependencies. After
    partition_sched_domain() gets fixed that is.

    > In practice of course, there may be details on the edges that depend on
    > the current SMP/NUMA limitations, such as:
    >
    > Magnus wrote:
    > > Regarding the #ifdef, it
    > > was added because partition_sched_domain() is only implemented for
    > > SMP. That symbol has no prototype or implementation when CONFIG_SMP is
    > > not set. Maybe it is better to add an empty inline function in
    > > linux/sched.h for !SMP?
    >
    > An empty inline partition_sched_domain() would be better than ifdef's
    > in cpuset.c, yes. Or at least, that's usually the case. Probably here
    > too.

    I agree.

    > In theory at least, I applaud Magnus's work here. The assymetry of the
    > SMP/NUMA define structure has always annoyed me slightly, and only been
    > explainable in my view as a consequence of the historical order of
    > development. I had a PC with a second memory board in an ISA slot,
    > which would qualify as a one CPU, two Memory Node system.
    >
    > Or what byte us in the future (that PC was a long time ago), the kinks
    > in the current setup might be a hitch in our side as we extend to
    > increasingly interesting architectures.

    Nice to hear that you like the idea.

    Maybe I should have broken down my patches into three smaller sets:

    1) i386: NUMA without SMP
    2) CPUSETS: NUMA || SMP
    3) i386: NUMA emulation

    If people like 1) then it's probably a good idea to convert other
    architectures too. Both 2) and 3) above are separate but related
    issues. And now seems like a good time to solve 2).

    So, Paul, please let me know if you prefer SMP || NUMA or no
    depencencies in the Kconfig. When I know that I will create a new
    patch that hopefully can get into -mm later on.

    > Aside - for those reading this thread on lkml, it originated
    > on linux-mm. It looks like Dave added lkml to the cc list.

    Huh? I sent my patches both to lkml and linux-mm...

    Thank you for the feedback!

    / magnus
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  • Next message: Rogério Brito: "Re: Strange disk corruption with Linux >= 2.6.13"

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    • Re: [PATCH 00/07][RFC] i386: NUMA emulation
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