linux-kernel - [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath

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Date:	Wed, 27 Jul 2016 10:47:59 -0400
From:	Janani Ravichandran <janani.rvchndrn@...il.com>
To:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:	riel@...riel.com, akpm@...ux-foundation.org, hannes@...pxchg.org,
	vdavydov@...tuozzo.com, mhocko@...e.com, vbabka@...e.cz,
	mgorman@...hsingularity.net, kirill.shutemov@...ux.intel.com,
	bywxiaobai@....com, rostedt@...dmis.org
Subject: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath

Add tracepoints to the slowpath code to gather some information.
The tracepoints can also be used to find out how much time was spent in
the slowpath.

Signed-off-by: Janani Ravichandran <janani.rvchndrn@...il.com>
---
 include/trace/events/kmem.h | 40 ++++++++++++++++++++++++++++++++++++++++
 mm/page_alloc.c             |  5 +++++
 2 files changed, 45 insertions(+)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 6b2e154..c19ab9f 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -169,6 +169,46 @@ TRACE_EVENT(mm_page_free,
 			__entry->order)
 );
 
+TRACE_EVENT(mm_slowpath_begin,
+
+	TP_PROTO(gfp_t gfp_mask, int order),
+
+	TP_ARGS(gfp_mask, order),
+
+	TP_STRUCT__entry(
+		__field(gfp_t, gfp_mask)
+		__field(int, order)
+	),
+
+	TP_fast_assign(
+		__entry->gfp_mask = gfp_mask;
+		__entry->order = order;
+	),
+
+	TP_printk("gfp_mask:%s order=%d",
+		show_gfp_flags(__entry->gfp_mask),
+		__entry->order)
+);
+
+TRACE_EVENT(mm_slowpath_end,
+
+	TP_PROTO(struct page *page),
+
+	TP_ARGS(page),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, pfn)
+	),
+
+	TP_fast_assign(
+		__entry->pfn = page ? page_to_pfn(page) : -1UL;
+	),
+
+	TP_printk("page=%p pfn=%lu",
+		__entry->pfn != -1UL ? pfn_to_page(__entry->pfn) : NULL,
+		__entry->pfn != -1UL ? __entry->pfn : 0)
+);
+
 TRACE_EVENT(mm_page_free_batched,
 
 	TP_PROTO(struct page *page, int cold),
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8b3e134..be9c688 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3595,6 +3595,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 				(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
 		gfp_mask &= ~__GFP_ATOMIC;
 
+	trace_mm_slowpath_begin(gfp_mask, order);
+
 retry:
 	if (gfp_mask & __GFP_KSWAPD_RECLAIM)
 		wake_all_kswapds(order, ac);
@@ -3769,6 +3771,9 @@ noretry:
 nopage:
 	warn_alloc_failed(gfp_mask, order, NULL);
 got_pg:
+
+	trace_mm_slowpath_end(page);
+
 	return page;
 }
 
-- 
2.7.0