Review Request: UseNUMAInterleaving

Deneau, Tom tom.deneau at
Mon May 16 10:54:11 PDT 2011

Please review this patch which adds a new flag called
UseNUMAInterleaving.  This flag provides a subset of the functionality
provided by UseNUMA, and its main purpose is to provide that subset on
OSes like Windows which do not support the full UseNUMA functionality.
In UseNUMA terminology, UseNUMAInterleaved makes all memory
"numa_global" which is implemented as interleaved.

The situations where this shows the biggest benefits would be:
   * Windows platforms with multiple numa nodes (eg, 4)
   * The JVM process is run across all the nodes (not affinitized to one node).

   * A workload that uses the majority of the cores in the machine, so
     that the heap is being accessed from many cores, including remote

   * Enough memory per node and a heap size such that the default heap
     placement policy on windows would end up with the heap (or
     nursery) placed on one node.

jbb2005 and SPECPower_ssj2008 are examples of such workloads.  In our
measurements, we have seen some cases where the performance with
UseNUMAInterleaving was 2.7x vs. the performance without. There were
gains of varying sizes across all systems.

As currently implemented this flag is ignored on Linux and Solaris
since they already support the full UseNUMA flag.

The webrev is at

Summary of changes:
   * Other than adding the new UseNUMAInterleaving global flag, all of
     the changes are in src/os/windows/vm/os_windows.cpp

   * Some static routines were added to set things up init time.  These
      * check that the required APIs (VirtualAllocExNuma,
        GetNumaHighestNodeNumber, GetNumaNodeProcessorMask) exist in
        the OS

      * build the list of numa nodes on which this process has affinity

   * Changes to os::reserve_memory
      * There was already a routine that reserved pages one page at a
        time (used for Individual Large Page Allocation on WS2003).
        This was abstracted to a separate routine, called
        allocate_pages_individually.  This gets called both for the
        Individual Large Page Allocation thing mentioned above and for
        UseNUMAInterleaving (for both small and large pages)

      * When used for NUMA Interleaving this just goes thru the numa
        node list in a round-robin fashion, using a different one for
        each chunk (with 4K pages, the minimum allocation granularity
        is 64K, with 2M pages it is 1 Page)

      * Whether we do just a reserve or a combined reserve/commit is
        determined by the caller of allocate_pages_individually

         * When used with large pages, we do a Reserve and Commit at
           the same time which is the way it always worked and the way
           it has to work on windows.

         * For small pages, only the reserve is done, the commit will
           come later. (which is the way it worked for

   * os::commit_memory changes
      * If UseNUMAIntereaving is true, os::commit_memory has to check
        whether it was being asked to commit memory that might have
        come from multiple Reserve allocations, if so, the commits
        must also be broken up.  We don't keep any data structure to
        keep track of this, we just use VirtualQuery which queries the
        properties of a VA range and can tell us how much came from
        one VirtualAlloc call.

I do not have a bug id for this.

-- Tom Deneau, AMD

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