tracing, page-allocator: add trace events for anti-fragmentation falling back to other migratetypes (e0fff1bd) · Commits · 戴 / test

Fragmentation avoidance depends on being able to use free pages from lists of the appropriate migrate type. In the event this is not possible, __rmqueue_fallback() selects a different list and in some circumstances change the migratetype of the pageblock. Simplistically, the more times this event occurs, the more likely that fragmentation will be a problem later for hugepage allocation at least but there are other considerations such as the order of page being split to satisfy the allocation. This patch adds a trace event for __rmqueue_fallback() that reports what page is being used for the fallback, the orders of relevant pages, the desired migratetype and the migratetype of the lists being used, whether the pageblock changed type and whether this event is important with respect to fragmentation avoidance or not. This information can be used to help analyse fragmentation avoidance and help decide whether min_free_kbytes should be increased or not. Signed-off-by:

Mel Gorman <mel@csn.ul.ie> Acked-by:

Rik van Riel <riel@redhat.com> Reviewed-by:

Ingo Molnar <mingo@elte.hu> Cc: Larry Woodman <lwoodman@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Li Ming Chun <macli@brc.ubc.ca> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/trace/events/kmem.h

+38 −0

Original line number	Diff line number	Diff line
		@@ -299,6 +299,44 @@ TRACE_EVENT(mm_page_alloc,
		show_gfp_flags(__entry->gfp_flags))
		);

		TRACE_EVENT(mm_page_alloc_extfrag,

		TP_PROTO(struct page *page,
		int alloc_order, int fallback_order,
		int alloc_migratetype, int fallback_migratetype),

		TP_ARGS(page,
		alloc_order, fallback_order,
		alloc_migratetype, fallback_migratetype),

		TP_STRUCT__entry(
		__field( struct page *, page )
		__field( int, alloc_order )
		__field( int, fallback_order )
		__field( int, alloc_migratetype )
		__field( int, fallback_migratetype )
		),

		TP_fast_assign(
		__entry->page = page;
		__entry->alloc_order = alloc_order;
		__entry->fallback_order = fallback_order;
		__entry->alloc_migratetype = alloc_migratetype;
		__entry->fallback_migratetype = fallback_migratetype;
		),

		TP_printk("page=%p pfn=%lu alloc_order=%d fallback_order=%d pageblock_order=%d alloc_migratetype=%d fallback_migratetype=%d fragmenting=%d change_ownership=%d",
		__entry->page,
		page_to_pfn(__entry->page),
		__entry->alloc_order,
		__entry->fallback_order,
		pageblock_order,
		__entry->alloc_migratetype,
		__entry->fallback_migratetype,
		__entry->fallback_order < pageblock_order,
		__entry->alloc_migratetype == __entry->fallback_migratetype)
		);

		#endif /* _TRACE_KMEM_H */

		/* This part must be outside protection */

mm/page_alloc.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -853,6 +853,10 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
		start_migratetype);

		expand(zone, page, order, current_order, area, migratetype);

		trace_mm_page_alloc_extfrag(page, order, current_order,
		start_migratetype, migratetype);

		return page;
		}
		}

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