writeback: add new tracepoints

Add 2 new trace points to the periodic write-back wake up case, just like we do in the 'bdi_queue_work()' function. Namely, introduce: 1. trace_writeback_wake_thread(bdi) 2. trace_writeback_wake_forker_thread(bdi) The first event is triggered every time we wake up a bdi thread to start periodic background write-out. The second event is triggered only when the bdi thread does not exist and should be created by the forker thread. This patch was suggested by Dave Chinner and Christoph Hellwig. Signed-off-by: Artem Bityutskiy <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
mna · Aug 7, 2010 · 6033202 · 6033202
1 parent b5048a6
commit 6033202
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diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
@@ -81,6 +81,8 @@ DEFINE_EVENT(writeback_class, name, \
 	TP_ARGS(bdi))
 
 DEFINE_WRITEBACK_EVENT(writeback_nowork);
+DEFINE_WRITEBACK_EVENT(writeback_wake_thread);
+DEFINE_WRITEBACK_EVENT(writeback_wake_forker_thread);
 DEFINE_WRITEBACK_EVENT(writeback_bdi_register);
 DEFINE_WRITEBACK_EVENT(writeback_bdi_unregister);
 DEFINE_WRITEBACK_EVENT(writeback_thread_start);

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
@@ -310,13 +310,15 @@ static void wakeup_timer_fn(unsigned long data)
 
 	spin_lock_bh(&bdi->wb_lock);
 	if (bdi->wb.task) {
+		trace_writeback_wake_thread(bdi);
 		wake_up_process(bdi->wb.task);
 	} else {
 		/*
 		 * When bdi tasks are inactive for long time, they are killed.
 		 * In this case we have to wake-up the forker thread which
 		 * should create and run the bdi thread.
 		 */
+		trace_writeback_wake_forker_thread(bdi);
 		wake_up_process(default_backing_dev_info.wb.task);
 	}
 	spin_unlock_bh(&bdi->wb_lock);