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Commit 0d3d062a authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

tracing, page-allocator: add trace event for page traffic related to the buddy lists 



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.

[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>
parent e0fff1bd

include/trace/events/kmem.h

+51 −0
Original line number Diff line number Diff line
@@ -299,6 +299,57 @@ TRACE_EVENT(mm_page_alloc, 
		show_gfp_flags(__entry->gfp_flags))

);



TRACE_EVENT(mm_page_alloc_zone_locked,



	TP_PROTO(struct page *page, unsigned int order, int migratetype),



	TP_ARGS(page, order, migratetype),



	TP_STRUCT__entry(

		__field(	struct page *,	page		)

		__field(	unsigned int,	order		)

		__field(	int,		migratetype	)

	),



	TP_fast_assign(

		__entry->page		= page;

		__entry->order		= order;

		__entry->migratetype	= migratetype;

	),



	TP_printk("page=%p pfn=%lu order=%u migratetype=%d percpu_refill=%d",

		__entry->page,

		page_to_pfn(__entry->page),

		__entry->order,

		__entry->migratetype,

		__entry->order == 0)

);



TRACE_EVENT(mm_page_pcpu_drain,



	TP_PROTO(struct page *page, int order, int migratetype),



	TP_ARGS(page, order, migratetype),



	TP_STRUCT__entry(

		__field(	struct page *,	page		)

		__field(	int,		order		)

		__field(	int,		migratetype	)

	),



	TP_fast_assign(

		__entry->page		= page;

		__entry->order		= order;

		__entry->migratetype	= migratetype;

	),



	TP_printk("page=%p pfn=%lu order=%d migratetype=%d",

		__entry->page,

		page_to_pfn(__entry->page),

		__entry->order,

		__entry->migratetype)

);



TRACE_EVENT(mm_page_alloc_extfrag,



	TP_PROTO(struct page *page,

mm/page_alloc.c

+3 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ 
#include <linux/page_cgroup.h>

#include <linux/debugobjects.h>

#include <linux/kmemleak.h>

#include <trace/events/kmem.h>



#include <asm/tlbflush.h>

#include <asm/div64.h>
@@ -535,6 +536,7 @@ static void free_pages_bulk(struct zone *zone, int count, 
		page = list_entry(list->prev, struct page, lru);

		/* have to delete it as __free_one_page list manipulates */

		list_del(&page->lru);

		trace_mm_page_pcpu_drain(page, order, page_private(page));

		__free_one_page(page, zone, order, page_private(page));

	}

	spin_unlock(&zone->lock);
@@ -890,6 +892,7 @@ static struct page *__rmqueue(struct zone *zone, unsigned int order, 
		}

	}



	trace_mm_page_alloc_zone_locked(page, order, migratetype);

	return page;

}