linux-kernel - [PATCH 2/4] mm: pagemap: Avoid unnecessary overhead when tracepoints are deactivated

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Message-Id: <1403079807-24690-3-git-send-email-mgorman@suse.de>
Date:	Wed, 18 Jun 2014 09:23:25 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>
Cc:	Jan Kara <jack@...e.cz>, Johannes Weiner <hannes@...xchg.org>,
	Jens Axboe <axboe@...nel.dk>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 2/4] mm: pagemap: Avoid unnecessary overhead when tracepoints are deactivated

The LRU insertion and activate tracepoints take PFN as a parameter forcing
the overhead to the caller.  Move the overhead to the tracepoint fast-assign
method to ensure the cost is only incurred when the tracepoint is active.

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 include/trace/events/pagemap.h | 16 +++++++---------
 mm/swap.c                      |  4 ++--
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/include/trace/events/pagemap.h b/include/trace/events/pagemap.h
index 1c9fabd..ce0803b 100644
--- a/include/trace/events/pagemap.h
+++ b/include/trace/events/pagemap.h
@@ -28,12 +28,10 @@ TRACE_EVENT(mm_lru_insertion,
 
 	TP_PROTO(
 		struct page *page,
-		unsigned long pfn,
-		int lru,
-		unsigned long flags
+		int lru
 	),
 
-	TP_ARGS(page, pfn, lru, flags),
+	TP_ARGS(page, lru),
 
 	TP_STRUCT__entry(
 		__field(struct page *,	page	)
@@ -44,9 +42,9 @@ TRACE_EVENT(mm_lru_insertion,
 
 	TP_fast_assign(
 		__entry->page	= page;
-		__entry->pfn	= pfn;
+		__entry->pfn	= page_to_pfn(page);
 		__entry->lru	= lru;
-		__entry->flags	= flags;
+		__entry->flags	= trace_pagemap_flags(page);
 	),
 
 	/* Flag format is based on page-types.c formatting for pagemap */
@@ -64,9 +62,9 @@ TRACE_EVENT(mm_lru_insertion,
 
 TRACE_EVENT(mm_lru_activate,
 
-	TP_PROTO(struct page *page, unsigned long pfn),
+	TP_PROTO(struct page *page),
 
-	TP_ARGS(page, pfn),
+	TP_ARGS(page),
 
 	TP_STRUCT__entry(
 		__field(struct page *,	page	)
@@ -75,7 +73,7 @@ TRACE_EVENT(mm_lru_activate,
 
 	TP_fast_assign(
 		__entry->page	= page;
-		__entry->pfn	= pfn;
+		__entry->pfn	= page_to_pfn(page);
 	),
 
 	/* Flag format is based on page-types.c formatting for pagemap */
diff --git a/mm/swap.c b/mm/swap.c
index 9e8e347..d10be45 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -501,7 +501,7 @@ static void __activate_page(struct page *page, struct lruvec *lruvec,
 		SetPageActive(page);
 		lru += LRU_ACTIVE;
 		add_page_to_lru_list(page, lruvec, lru);
-		trace_mm_lru_activate(page, page_to_pfn(page));
+		trace_mm_lru_activate(page);
 
 		__count_vm_event(PGACTIVATE);
 		update_page_reclaim_stat(lruvec, file, 1);
@@ -996,7 +996,7 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
 	SetPageLRU(page);
 	add_page_to_lru_list(page, lruvec, lru);
 	update_page_reclaim_stat(lruvec, file, active);
-	trace_mm_lru_insertion(page, page_to_pfn(page), lru, trace_pagemap_flags(page));
+	trace_mm_lru_insertion(page, lru);
 }
 
 /*
-- 
1.8.4.5

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