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Mel Gorman
0d3d062a6e
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 examined. 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. [[email protected]: fix build] Signed-off-by: Mel Gorman <[email protected]> Acked-by: Rik van Riel <[email protected]> Reviewed-by: Ingo Molnar <[email protected]> Cc: Larry Woodman <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Li Ming Chun <[email protected]> Reviewed-by: KOSAKI Motohiro <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>