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Subject[PATCHv4 14/14] writeback: add new tracepoints
Date
From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

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_wakeup(bdi)
2. trace_writeback_wakeup_nothread(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 <david@fromorbit.com>

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---
include/trace/events/writeback.h | 2 ++
mm/backing-dev.c | 3 +++
2 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 84ab72d..eb07d48 100644
--- 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_wakeup);
+DEFINE_WRITEBACK_EVENT(writeback_wakeup_nothread);
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
index ce105fc..22fc506 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -308,6 +308,8 @@ static void wakeup_timer_fn(unsigned long data)
{
struct backing_dev_info *bdi = (struct backing_dev_info *)data;

+ trace_writeback_wakeup(bdi);
+
spin_lock(&bdi->wb_lock);
if (bdi->wb.task) {
wake_up_process(bdi->wb.task);
@@ -317,6 +319,7 @@ static void wakeup_timer_fn(unsigned long data)
* In this case we have to wake-up the forker thread which
* should create and run the bdi thread.
*/
+ trace_writeback_wakeup_nothread(bdi);
wake_up_process(default_backing_dev_info.wb.task);
}
spin_unlock(&bdi->wb_lock);
--
1.7.1.1


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