linux-kernel - [Patch v2] [PATCH] mm/page_alloc: Fix tracepoint mm_page_alloc_zone

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Message-Id: <20220512025307.57924-1-vvghjk1234@gmail.com>
Date:   Thu, 12 May 2022 11:53:07 +0900
From:   Wonhyuk Yang <vvghjk1234@...il.com>
To:     Mel Gorman <mgorman@...e.de>, Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Wonhyuk Yang <vvghjk1234@...il.com>,
        Baik Song An <bsahn@...i.re.kr>,
        Hong Yeon Kim <kimhy@...i.re.kr>,
        Taeung Song <taeung@...llinux.co.kr>, linuxgeek@...uxgeek.io,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [Patch v2] [PATCH] mm/page_alloc: Fix tracepoint mm_page_alloc_zone_locked()

Currently, trace point mm_page_alloc_zone_locked() doesn't show
correct information.

First, when alloc_flag has ALLOC_HARDER/ALLOC_CMA, page can
be allocated from MIGRATE_HIGHATOMIC/MIGRATE_CMA. Nevertheless,
tracepoint use requested migration type not MIGRATE_HIGHATOMIC and
MIGRATE_CMA.

Second, after Commit 44042b4498728 ("mm/page_alloc: allow high-order
pages to be stored on the per-cpu lists") percpu-list can store
high order pages. But trace point determine whether it is a refiil
of percpu-list by comparing requested order and 0.

To handle these problems, make mm_page_alloc_zone_locked() only be
called by __rmqueue_smallest with correct migration type. With a
new argument called percpu_refill, it can show roughly whether it
is a refill of percpu-list.

Cc: Baik Song An <bsahn@...i.re.kr>
Cc: Hong Yeon Kim <kimhy@...i.re.kr>
Cc: Taeung Song <taeung@...llinux.co.kr>
Cc: linuxgeek@...uxgeek.io
Signed-off-by: Wonhyuk Yang <vvghjk1234@...il.com>
---
v1 -> v2: Simplify determining percpu-refill suggested by Mel Gorman

 include/trace/events/kmem.h | 14 +++++++++-----
 mm/page_alloc.c             | 13 +++++--------
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index ddc8c944f417..f89fb3afcd46 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -229,20 +229,23 @@ TRACE_EVENT(mm_page_alloc,
 
 DECLARE_EVENT_CLASS(mm_page,
 
-	TP_PROTO(struct page *page, unsigned int order, int migratetype),
+	TP_PROTO(struct page *page, unsigned int order, int migratetype,
+		 int percpu_refill),
 
-	TP_ARGS(page, order, migratetype),
+	TP_ARGS(page, order, migratetype, percpu_refill),
 
 	TP_STRUCT__entry(
 		__field(	unsigned long,	pfn		)
 		__field(	unsigned int,	order		)
 		__field(	int,		migratetype	)
+		__field(	int,		percpu_refill	)
 	),
 
 	TP_fast_assign(
 		__entry->pfn		= page ? page_to_pfn(page) : -1UL;
 		__entry->order		= order;
 		__entry->migratetype	= migratetype;
+		__entry->percpu_refill	= percpu_refill;
 	),
 
 	TP_printk("page=%p pfn=0x%lx order=%u migratetype=%d percpu_refill=%d",
@@ -250,14 +253,15 @@ DECLARE_EVENT_CLASS(mm_page,
 		__entry->pfn != -1UL ? __entry->pfn : 0,
 		__entry->order,
 		__entry->migratetype,
-		__entry->order == 0)
+		__entry->percpu_refill)
 );
 
 DEFINE_EVENT(mm_page, mm_page_alloc_zone_locked,
 
-	TP_PROTO(struct page *page, unsigned int order, int migratetype),
+	TP_PROTO(struct page *page, unsigned int order, int migratetype,
+		 int percpu_refill),
 
-	TP_ARGS(page, order, migratetype)
+	TP_ARGS(page, order, migratetype, percpu_refill)
 );
 
 TRACE_EVENT(mm_page_pcpu_drain,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0e42038382c1..e906ac274586 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2476,6 +2476,9 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
 		del_page_from_free_list(page, zone, current_order);
 		expand(zone, page, order, current_order, migratetype);
 		set_pcppage_migratetype(page, migratetype);
+		trace_mm_page_alloc_zone_locked(page, order, migratetype, 
+				pcp_allowed_order(order) &&
+				migratetype < MIGRATE_PCPTYPES);
 		return page;
 	}
 
@@ -2999,7 +3002,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype,
 		    zone_page_state(zone, NR_FREE_PAGES) / 2) {
 			page = __rmqueue_cma_fallback(zone, order);
 			if (page)
-				goto out;
+				return page;
 		}
 	}
 retry:
@@ -3012,9 +3015,6 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype,
 								alloc_flags))
 			goto retry;
 	}
-out:
-	if (page)
-		trace_mm_page_alloc_zone_locked(page, order, migratetype);
 	return page;
 }
 
@@ -3733,11 +3733,8 @@ struct page *rmqueue(struct zone *preferred_zone,
 		 * reserved for high-order atomic allocation, so order-0
 		 * request should skip it.
 		 */
-		if (order > 0 && alloc_flags & ALLOC_HARDER) {
+		if (order > 0 && alloc_flags & ALLOC_HARDER)
 			page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
-			if (page)
-				trace_mm_page_alloc_zone_locked(page, order, migratetype);
-		}
 		if (!page) {
 			page = __rmqueue(zone, order, migratetype, alloc_flags);
 			if (!page)
-- 
2.30.2