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  • Mel Gorman's avatar
    tracing, page-allocator: add trace event for page traffic related to the buddy lists · 0d3d062a
    Mel Gorman authored
    The page allocation trace event reports that a page was successfully
    allocated but it does not specify where it came from.  When analysing
    performance, it can be important to distinguish between pages coming from
    the per-cpu allocator and pages coming from the buddy lists as the latter
    requires the zone lock to the taken and more data structures to be
    This patch adds a trace event for __rmqueue reporting when a page is being
    allocated from the buddy lists.  It distinguishes between being called to
    refill the per-cpu lists or whether it is a high-order allocation.
    Similarly, this patch adds an event to catch when the PCP lists are being
    drained a little and pages are going back to the buddy lists.
    This is trickier to draw conclusions from but high activity on those
    events could explain why there were a large number of cache misses on a
    page-allocator-intensive workload.  The coalescing and splitting of
    buddies involves a lot of writing of page metadata and cache line bounces
    not to mention the acquisition of an interrupt-safe lock necessary to
    enter this path.
    [ fix build]
    Signed-off-by: default avatarMel Gorman <>
    Acked-by: default avatarRik van Riel <>
    Reviewed-by: default avatarIngo Molnar <>
    Cc: Larry Woodman <>
    Cc: Peter Zijlstra <>
    Cc: Li Ming Chun <>
    Reviewed-by: default avatarKOSAKI Motohiro <>
    Signed-off-by: default avatarAndrew Morton <>
    Signed-off-by: default avatarLinus Torvalds <>