linux-kernel - [PATCH v3] mm, tracing: improve rss

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Date:   Fri, 12 Mar 2021 14:23:43 +0200
From:   Ovidiu Panait <ovidiu.panait@...driver.com>
To:     linux-kernel@...r.kernel.org
Cc:     rostedt@...dmis.org, akpm@...ux-foundation.org, mingo@...hat.com,
        christian@...uner.io
Subject: [PATCH v3] 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

Use TRACE_DEFINE_ENUM()/__print_symbolic() logic to map the enum values to
the strings they represent, so that userspace tools can also parse the raw
data correctly.

Signed-off-by: Ovidiu Panait <ovidiu.panait@...driver.com>
Suggested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
v3: add "Suggested-by" and "Reviewed-by" tags from Steven Rostedt
v2: rework the patch so that user space tools can parse the raw
    data correctly

 include/trace/events/kmem.h | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 3a60b6b6db32..829a75692cc0 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -343,6 +343,26 @@ static unsigned int __maybe_unused mm_ptr_to_hash(const void *ptr)
 #define __PTR_TO_HASHVAL
 #endif
 
+#define TRACE_MM_PAGES		\
+	EM(MM_FILEPAGES)	\
+	EM(MM_ANONPAGES)	\
+	EM(MM_SWAPENTS)		\
+	EMe(MM_SHMEMPAGES)
+
+#undef EM
+#undef EMe
+
+#define EM(a)	TRACE_DEFINE_ENUM(a);
+#define EMe(a)	TRACE_DEFINE_ENUM(a);
+
+TRACE_MM_PAGES
+
+#undef EM
+#undef EMe
+
+#define EM(a)	{ a, #a },
+#define EMe(a)	{ a, #a }
+
 TRACE_EVENT(rss_stat,
 
 	TP_PROTO(struct mm_struct *mm,
@@ -365,10 +385,10 @@ 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,
+		__print_symbolic(__entry->member, TRACE_MM_PAGES),
 		__entry->size)
 	);
 #endif /* _TRACE_KMEM_H */
-- 
2.17.1