writeback: trace event 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>
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index ffb5deb..0ce9f06 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -271,6 +271,79 @@
)
);
+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,
+ long pause,
+ unsigned long start_time),
+
+ TP_ARGS(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty,
+ dirty_ratelimit, task_ratelimit,
+ dirtied, 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, paused)
+ __field( long, pause)
+ ),
+
+ 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->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 "
+ "paused=%lu pause=%ld",
+ __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->paused, /* ms */
+ __entry->pause /* ms */
+ )
+);
+
DECLARE_EVENT_CLASS(writeback_congest_waited_template,
TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index e3c2d8b..45d36f7 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1103,12 +1103,34 @@
pos_ratio >> RATELIMIT_CALC_SHIFT;
pause = (HZ * pages_dirtied) / (task_ratelimit | 1);
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,
+ pause,
+ start_time);
pause = 1; /* avoid resetting nr_dirtied_pause below */
break;
}
pause = min(pause, max_pause);
pause:
+ trace_balance_dirty_pages(bdi,
+ dirty_thresh,
+ background_thresh,
+ nr_dirty,
+ bdi_thresh,
+ bdi_dirty,
+ dirty_ratelimit,
+ task_ratelimit,
+ pages_dirtied,
+ pause,
+ start_time);
__set_current_state(TASK_UNINTERRUPTIBLE);
io_schedule_timeout(pause);