• Mel Gorman's avatar
    mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate · b8593bfd
    Mel Gorman authored
    The PTE scanning rate and fault rates are two of the biggest sources of
    system CPU overhead with automatic NUMA placement.  Ideally a proper policy
    would detect if a workload was properly placed, schedule and adjust the
    PTE scanning rate accordingly. We do not track the necessary information
    to do that but we at least know if we migrated or not.
    
    This patch scans slower if a page was not migrated as the result of a
    NUMA hinting fault up to sysctl_numa_balancing_scan_period_max which is
    now higher than the previous default. Once every minute it will reset
    the scanner in case of phase changes.
    
    This is hilariously crude and the numbers are arbitrary. Workloads will
    converge quite slowly in comparison to what a proper policy should be able
    to do. On the plus side, we will chew up less CPU for workloads that have
    no need for automatic balancing.
    Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    b8593bfd
core.c 194 KB