linux-kernel - [PATCH] mm, tracing: improve rss

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Message-Id: <20210308185000.14052-1-ovidiu.panait@windriver.com>
Date:   Mon,  8 Mar 2021 20:50:00 +0200
From:   Ovidiu Panait <ovidiu.panait@...driver.com>
To:     linux-kernel@...r.kernel.org
Cc:     akpm@...ux-foundation.org, rostedt@...dmis.org, mingo@...hat.com,
        christian@...uner.io
Subject: [PATCH] mm, tracing: improve rss_stat tracepoint message

Adjust the rss_stat tracepoint to print the name of the resident page type
that got updated(e.g. MM_ANONPAGES/MM_FILEPAGES), rather than the numeric
index corresponding to it(the __entry->member value):

Before this patch:
------------------
rss_stat: mm_id=1216113068 curr=0 member=1 size=28672B
rss_stat: mm_id=1216113068 curr=0 member=1 size=0B
rss_stat: mm_id=534402304 curr=1 member=0 size=188416B
rss_stat: mm_id=534402304 curr=1 member=1 size=40960B

After this patch:
-----------------
rss_stat: mm_id=1726253524 curr=1 type=MM_ANONPAGES size=40960B
rss_stat: mm_id=1726253524 curr=1 type=MM_FILEPAGES size=663552B
rss_stat: mm_id=1726253524 curr=1 type=MM_ANONPAGES size=65536B
rss_stat: mm_id=1726253524 curr=1 type=MM_FILEPAGES size=647168B

Also, make the resident_page_types[] array in kernel/fork.c non-static so
that it can be reused from tracing code.

Signed-off-by: Ovidiu Panait <ovidiu.panait@...driver.com>
---
 include/linux/mm.h          | 2 ++
 include/trace/events/kmem.h | 5 +++--
 kernel/fork.c               | 2 +-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 89fca443e6f1..7916112d5952 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3141,5 +3141,7 @@ void mem_dump_obj(void *object);
 static inline void mem_dump_obj(void *object) {}
 #endif
 
+extern const char * const resident_page_types[];
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */
diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 3a60b6b6db32..623506917cd0 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -5,6 +5,7 @@
 #if !defined(_TRACE_KMEM_H) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_KMEM_H
 
+#include <linux/mm.h>
 #include <linux/types.h>
 #include <linux/tracepoint.h>
 #include <trace/events/mmflags.h>
@@ -365,10 +366,10 @@ TRACE_EVENT(rss_stat,
 		__entry->size = (count << PAGE_SHIFT);
 	),
 
-	TP_printk("mm_id=%u curr=%d member=%d size=%ldB",
+	TP_printk("mm_id=%u curr=%d type=%s size=%ldB",
 		__entry->mm_id,
 		__entry->curr,
-		__entry->member,
+		resident_page_types[__entry->member],
 		__entry->size)
 	);
 #endif /* _TRACE_KMEM_H */
diff --git a/kernel/fork.c b/kernel/fork.c
index d3171e8e88e5..b30fe8ca56b3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -128,7 +128,7 @@ static int max_threads;		/* tunable limit on nr_threads */
 
 #define NAMED_ARRAY_INDEX(x)	[x] = __stringify(x)
 
-static const char * const resident_page_types[] = {
+const char * const resident_page_types[] = {
 	NAMED_ARRAY_INDEX(MM_FILEPAGES),
 	NAMED_ARRAY_INDEX(MM_ANONPAGES),
 	NAMED_ARRAY_INDEX(MM_SWAPENTS),
-- 
2.25.1