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Subject[PATCH 09/18] writeback: trace balance_dirty_pages
Useful for analyzing the dynamics of the throttling algorithms and
debugging user reported problems.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
include/trace/events/writeback.h | 81 +++++++++++++++++++++++++++++
mm/page-writeback.c | 24 ++++++++
2 files changed, 105 insertions(+)
--- linux-next.orig/include/trace/events/writeback.h 2011-08-29 19:52:11.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2011-08-29 19:52:13.000000000 +0800
@@ -272,6 +272,87 @@ TRACE_EVENT(dirty_ratelimit,
)
);

+TRACE_EVENT(balance_dirty_pages,
+
+ TP_PROTO(struct backing_dev_info *bdi,
+ unsigned long thresh,
+ unsigned long bg_thresh,
+ unsigned long dirty,
+ unsigned long bdi_thresh,
+ unsigned long bdi_dirty,
+ unsigned long dirty_ratelimit,
+ unsigned long task_ratelimit,
+ unsigned long dirtied,
+ unsigned long period,
+ long pause,
+ unsigned long start_time),
+
+ TP_ARGS(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty,
+ dirty_ratelimit, task_ratelimit,
+ dirtied, period, pause, start_time),
+
+ TP_STRUCT__entry(
+ __array( char, bdi, 32)
+ __field(unsigned long, limit)
+ __field(unsigned long, setpoint)
+ __field(unsigned long, dirty)
+ __field(unsigned long, bdi_setpoint)
+ __field(unsigned long, bdi_dirty)
+ __field(unsigned long, dirty_ratelimit)
+ __field(unsigned long, task_ratelimit)
+ __field(unsigned int, dirtied)
+ __field(unsigned int, dirtied_pause)
+ __field(unsigned long, period)
+ __field( long, think)
+ __field( long, pause)
+ __field(unsigned long, paused)
+ ),
+
+ TP_fast_assign(
+ unsigned long freerun = (thresh + bg_thresh) / 2;
+ strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
+
+ __entry->limit = global_dirty_limit;
+ __entry->setpoint = (global_dirty_limit + freerun) / 2;
+ __entry->dirty = dirty;
+ __entry->bdi_setpoint = __entry->setpoint *
+ bdi_thresh / (thresh + 1);
+ __entry->bdi_dirty = bdi_dirty;
+ __entry->dirty_ratelimit = KBps(dirty_ratelimit);
+ __entry->task_ratelimit = KBps(task_ratelimit);
+ __entry->dirtied = dirtied;
+ __entry->dirtied_pause = current->nr_dirtied_pause;
+ __entry->think = current->dirty_paused_when == 0 ? 0 :
+ (long)(jiffies - current->dirty_paused_when) * 1000/HZ;
+ __entry->period = period * 1000 / HZ;
+ __entry->pause = pause * 1000 / HZ;
+ __entry->paused = (jiffies - start_time) * 1000 / HZ;
+ ),
+
+
+ TP_printk("bdi %s: "
+ "limit=%lu setpoint=%lu dirty=%lu "
+ "bdi_setpoint=%lu bdi_dirty=%lu "
+ "dirty_ratelimit=%lu task_ratelimit=%lu "
+ "dirtied=%u dirtied_pause=%u "
+ "period=%lu think=%ld pause=%ld paused=%lu",
+ __entry->bdi,
+ __entry->limit,
+ __entry->setpoint,
+ __entry->dirty,
+ __entry->bdi_setpoint,
+ __entry->bdi_dirty,
+ __entry->dirty_ratelimit,
+ __entry->task_ratelimit,
+ __entry->dirtied,
+ __entry->dirtied_pause,
+ __entry->period, /* ms */
+ __entry->think, /* ms */
+ __entry->pause, /* ms */
+ __entry->paused /* ms */
+ )
+);
+
DECLARE_EVENT_CLASS(writeback_congest_waited_template,

TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),
--- linux-next.orig/mm/page-writeback.c 2011-08-29 19:52:11.000000000 +0800
+++ linux-next/mm/page-writeback.c 2011-08-29 19:52:13.000000000 +0800
@@ -1062,6 +1062,18 @@ static void balance_dirty_pages(struct a
* do a reset, as it may be a light dirtier.
*/
if (unlikely(pause <= 0)) {
+ trace_balance_dirty_pages(bdi,
+ dirty_thresh,
+ background_thresh,
+ nr_dirty,
+ bdi_thresh,
+ bdi_dirty,
+ dirty_ratelimit,
+ task_ratelimit,
+ pages_dirtied,
+ period,
+ pause,
+ start_time);
if (pause < -HZ) {
current->dirty_paused_when = now;
current->nr_dirtied = 0;
@@ -1075,6 +1087,18 @@ static void balance_dirty_pages(struct a
pause = min(pause, (long)MAX_PAUSE);

pause:
+ trace_balance_dirty_pages(bdi,
+ dirty_thresh,
+ background_thresh,
+ nr_dirty,
+ bdi_thresh,
+ bdi_dirty,
+ dirty_ratelimit,
+ task_ratelimit,
+ pages_dirtied,
+ period,
+ pause,
+ start_time);
__set_current_state(TASK_UNINTERRUPTIBLE);
io_schedule_timeout(pause);




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