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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>
This commit is contained in:
Wu Fengguang 2010-08-29 23:33:20 -06:00
parent b48c104d22
commit ece13ac31b
2 changed files with 95 additions and 0 deletions
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73
include/trace/events/writeback.h
View File

@ -271,6 +271,79 @@ TRACE_EVENT(bdi_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,
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),

22
mm/page-writeback.c
View File

@ -1103,12 +1103,34 @@ static void balance_dirty_pages(struct address_space *mapping,
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);