• Paul Jackson's avatar
    [PATCH] cpuset memory spread basic implementation · 825a46af
    Paul Jackson authored
    
    
    This patch provides the implementation and cpuset interface for an alternative
    memory allocation policy that can be applied to certain kinds of memory
    allocations, such as the page cache (file system buffers) and some slab caches
    (such as inode caches).
    
    The policy is called "memory spreading." If enabled, it spreads out these
    kinds of memory allocations over all the nodes allowed to a task, instead of
    preferring to place them on the node where the task is executing.
    
    All other kinds of allocations, including anonymous pages for a tasks stack
    and data regions, are not affected by this policy choice, and continue to be
    allocated preferring the node local to execution, as modified by the NUMA
    mempolicy.
    
    There are two boolean flag files per cpuset that control where the kernel
    allocates pages for the file system buffers and related in kernel data
    structures.  They are called 'memory_spread_page' and 'memory_spread_slab'.
    
    If the per-cpuset boolean flag file 'memory_spread_page' is set, then the
    kernel will spread the file system buffers (page cache) evenly over all the
    nodes that the faulting task is allowed to use, instead of preferring to put
    those pages on the node where the task is running.
    
    If the per-cpuset boolean flag file 'memory_spread_slab' is set, then the
    kernel will spread some file system related slab caches, such as for inodes
    and dentries evenly over all the nodes that the faulting task is allowed to
    use, instead of preferring to put those pages on the node where the task is
    running.
    
    The implementation is simple.  Setting the cpuset flags 'memory_spread_page'
    or 'memory_spread_cache' turns on the per-process flags PF_SPREAD_PAGE or
    PF_SPREAD_SLAB, respectively, for each task that is in the cpuset or
    subsequently joins that cpuset.  In subsequent patches, the page allocation
    calls for the affected page cache and slab caches are modified to perform an
    inline check for these flags, and if set, a call to a new routine
    cpuset_mem_spread_node() returns the node to prefer for the allocation.
    
    The cpuset_mem_spread_node() routine is also simple.  It uses the value of a
    per-task rotor cpuset_mem_spread_rotor to select the next node in the current
    tasks mems_allowed to prefer for the allocation.
    
    This policy can provide substantial improvements for jobs that need to place
    thread local data on the corresponding node, but that need to access large
    file system data sets that need to be spread across the several nodes in the
    jobs cpuset in order to fit.  Without this patch, especially for jobs that
    might have one thread reading in the data set, the memory allocation across
    the nodes in the jobs cpuset can become very uneven.
    
    A couple of Copyright year ranges are updated as well.  And a couple of email
    addresses that can be found in the MAINTAINERS file are removed.
    Signed-off-by: default avatarPaul Jackson <pj@sgi.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    825a46af
cpuset.c 69.5 KB