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Commit 755f0225 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
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vmscan: tracing: add trace event when a page is written 



Add a trace event for when page reclaim queues a page for IO and records
whether it is synchronous or asynchronous.  Excessive synchronous IO for a
process can result in noticeable stalls during direct reclaim.  Excessive
IO from page reclaim may indicate that the system is seriously under
provisioned for the amount of dirty pages that exist.

Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarLarry Woodman <lwoodman@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a8a94d15

include/trace/events/vmscan.h

+41 −0
Original line number Diff line number Diff line
@@ -8,6 +8,24 @@ 
#include <linux/tracepoint.h>

#include "gfpflags.h"



#define RECLAIM_WB_ANON		0x0001u

#define RECLAIM_WB_FILE		0x0002u

#define RECLAIM_WB_SYNC		0x0004u

#define RECLAIM_WB_ASYNC	0x0008u



#define show_reclaim_flags(flags)				\

	(flags) ? __print_flags(flags, "|",			\

		{RECLAIM_WB_ANON,	"RECLAIM_WB_ANON"},	\

		{RECLAIM_WB_FILE,	"RECLAIM_WB_FILE"},	\

		{RECLAIM_WB_SYNC,	"RECLAIM_WB_SYNC"},	\

		{RECLAIM_WB_ASYNC,	"RECLAIM_WB_ASYNC"}	\

		) : "RECLAIM_WB_NONE"



#define trace_reclaim_flags(page, sync) ( \

	(page_is_file_cache(page) ? RECLAIM_WB_FILE : RECLAIM_WB_ANON) | \

	(sync == PAGEOUT_IO_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC)   \

	)



TRACE_EVENT(mm_vmscan_kswapd_sleep,



	TP_PROTO(int nid),
@@ -155,6 +173,29 @@ TRACE_EVENT(mm_vmscan_lru_isolate, 
		__entry->nr_lumpy_failed)

);



TRACE_EVENT(mm_vmscan_writepage,



	TP_PROTO(struct page *page,

		int reclaim_flags),



	TP_ARGS(page, reclaim_flags),



	TP_STRUCT__entry(

		__field(struct page *, page)

		__field(int, reclaim_flags)

	),



	TP_fast_assign(

		__entry->page = page;

		__entry->reclaim_flags = reclaim_flags;

	),



	TP_printk("page=%p pfn=%lu flags=%s",

		__entry->page,

		page_to_pfn(__entry->page),

		show_reclaim_flags(__entry->reclaim_flags))

);



#endif /* _TRACE_VMSCAN_H */



/* This part must be outside protection */

mm/vmscan.c

+2 −0
Original line number Diff line number Diff line
@@ -401,6 +401,8 @@ static pageout_t pageout(struct page *page, struct address_space *mapping, 
			/* synchronous write or broken a_ops? */

			ClearPageReclaim(page);

		}

		trace_mm_vmscan_writepage(page,

			trace_reclaim_flags(page, sync_writeback));

		inc_zone_page_state(page, NR_VMSCAN_WRITE);

		return PAGE_SUCCESS;

	}