linux-kernel - [PATCH v2 1/2] tracing/events: block: track and print if unplug was explicit or schedule

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Date:   Fri, 13 Apr 2018 18:36:21 +0200
From:   Steffen Maier <maier@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Li Zefan <lizefan@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Steffen Maier <maier@...ux.ibm.com>
Subject: [PATCH v2 1/2] tracing/events: block: track and print if unplug was explicit or schedule

Just like blktrace distinguishes explicit and schedule by means of
BLK_TA_UNPLUG_IO and BLK_TA_UNPLUG_TIMER, actually make use of the
existing argument "explicit" to distinguish the two cases in the one
common tracepoint block_unplug.

Complements v2.6.39 commit 49cac01e1fa7 ("block: make unplug timer trace
event correspond to the schedule() unplug") and commit d9c978331790
("block: remove block_unplug_timer() trace point").

Signed-off-by: Steffen Maier <maier@...ux.ibm.com>
---

Changes since v1:
Use 0 and 1 instead of false and true for __print_symbolic table.
Now "trace-cmd report" can decode it. [Steven Rostedt]

 include/trace/events/block.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/block.h b/include/trace/events/block.h
index 81b43f5bdf23..e90bb6eb8097 100644
--- a/include/trace/events/block.h
+++ b/include/trace/events/block.h
@@ -470,6 +470,11 @@ TRACE_EVENT(block_plug,
 	TP_printk("[%s]", __entry->comm)
 );
 
+#define show_block_unplug_explicit(val)		\
+	__print_symbolic(val,			\
+			 {0, "schedule"},	\
+			 {1, "explicit"})
+
 DECLARE_EVENT_CLASS(block_unplug,
 
 	TP_PROTO(struct request_queue *q, unsigned int depth, bool explicit),
@@ -478,15 +483,18 @@ DECLARE_EVENT_CLASS(block_unplug,
 
 	TP_STRUCT__entry(
 		__field( int,		nr_rq			)
+		__field( bool,		explicit		)
 		__array( char,		comm,	TASK_COMM_LEN	)
 	),
 
 	TP_fast_assign(
 		__entry->nr_rq = depth;
+		__entry->explicit = explicit;
 		memcpy(__entry->comm, current->comm, TASK_COMM_LEN);
 	),
 
-	TP_printk("[%s] %d", __entry->comm, __entry->nr_rq)
+	TP_printk("[%s] %d %s", __entry->comm, __entry->nr_rq,
+		  show_block_unplug_explicit(__entry->explicit))
 );
 
 /**
-- 
2.13.5