• 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.
    [akpm@linux-foundation.org: fix build]
    Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
    Acked-by: default avatarRik van Riel <riel@redhat.com>
    Reviewed-by: default avatarIngo Molnar <mingo@elte.hu>
    Cc: Larry Woodman <lwoodman@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Li Ming Chun <macli@brc.ubc.ca>
    Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>