Re: AMD64 NUMA-awareness?

From: Scott Long (scottl_at_samsco.org)
Date: 05/19/05

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    Date: Thu, 19 May 2005 12:38:15 -0600
To: Jung-uk Kim <jkim@niksun.com>

    Jung-uk Kim wrote:

    > ULE scheduler paper
    > (http://www.usenix.org/publications/library/proceedings/bsdcon03/tech/roberson.html)
    > says:
    >
    > 'SMT introduces a concept of non-uniform processors into ULE which
    > could be extended to support NUMA. The concept of expressing the
    > penalty for migration through the use of separate queues could be
    > further developed to include a local and global load-balancing
    > policy. At the time of this writing, however, FreeBSD does not
    > support any true NUMA capable machines and so this is left until such
    > time that it does.'
    >
    > I am not sure about the meaning of 'true NUMA capable machines' but
    > AMD64 is ccNUMA unless I am completely mistaken, and FreeBSD/amd64 is
    > well-supported. Even multicore processors are available now and
    > Intel is going to release dual-core processors with HTT to make
    > matters worse.
    >

    Even HTT by itself presents some interesting scheduling challenges that
    need to be accounted for.

    > Is there anybody working on this?

    Jeff stated recently that both ULE and 4BSD have some very primitive
    awareness of topology, but that much more work is needed. NUMA would
    also benefit from the UMA memory allocator understanding memory topology
    and working with the scheduler to keep processes on CPUs that are
    closest to their memory. Unfortunately, there doesn't appear to be
    much work going on, so if anyone is interested, it's a great project and
    I encourage all to help.

    Scott

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