[PATCH 32/47] writeback: extend balance_dirty_pages() trace event

Wu Fengguang
2010-12-13T06:54:45Z

[-- Attachment #1: writeback-trace-add-fields.patch --]
[-- Type: text/plain, Size: 4751 bytes --]

Make it more useful for analyzing the dynamics of the throttling
algorithms, and helpful for debugging user reported problems.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
include/trace/events/writeback.h | 52 +++++++++++++++++++++--------
mm/page-writeback.c | 14 +++++++
2 files changed, 53 insertions(+), 13 deletions(-)

--- linux-next.orig/include/trace/events/writeback.h 2010-12-09 12:21:04.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2010-12-09 12:24:49.000000000 +0800
@@ -149,35 +149,53 @@ DEFINE_WBC_EVENT(wbc_writeback_written);
DEFINE_WBC_EVENT(wbc_writeback_wait);
DEFINE_WBC_EVENT(wbc_writepage);

+#define KBps(x) ((x) << (PAGE_SHIFT - 10))
#define BDP_PERCENT(a, b, c) ((__entry->a - __entry->b) * 100 * c + \
__entry->bdi_limit/2) / (__entry->bdi_limit|1)
+
TRACE_EVENT(balance_dirty_pages,

TP_PROTO(struct backing_dev_info *bdi,
long bdi_dirty,
+ long avg_dirty,
long bdi_limit,
long task_limit,
- long pages_dirtied,
+ long dirtied,
+ long task_bw,
+ long period,
long pause),

- TP_ARGS(bdi, bdi_dirty, bdi_limit, task_limit,
- pages_dirtied, pause),
+ TP_ARGS(bdi, bdi_dirty, avg_dirty, bdi_limit, task_limit,
+ dirtied, task_bw, period, pause),

TP_STRUCT__entry(
__array(char, bdi, 32)
__field(long, bdi_dirty)
+ __field(long, avg_dirty)
__field(long, bdi_limit)
__field(long, task_limit)
- __field(long, pages_dirtied)
+ __field(long, dirtied)
+ __field(long, bdi_bw)
+ __field(long, base_bw)
+ __field(long, task_bw)
+ __field(long, period)
+ __field(long, think)
__field(long, pause)
),

TP_fast_assign(
strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
__entry->bdi_dirty = bdi_dirty;
+ __entry->avg_dirty = avg_dirty;
__entry->bdi_limit = bdi_limit;
__entry->task_limit = task_limit;
- __entry->pages_dirtied = pages_dirtied;
+ __entry->dirtied = dirtied;
+ __entry->bdi_bw = KBps(bdi->write_bandwidth);
+ __entry->base_bw = KBps(bdi->throttle_bandwidth);
+ __entry->task_bw = KBps(task_bw);
+ __entry->think = current->paused_when == 0 ? 0 :
+ (long)(jiffies - current->paused_when) * 1000 / HZ;
+ __entry->period = period * 1000 / HZ;
__entry->pause = pause * 1000 / HZ;
),

@@ -191,19 +209,27 @@ TRACE_EVENT(balance_dirty_pages,
*
* Reasonable large gaps help produce smooth pause times.
*/
- TP_printk("bdi=%s bdi_dirty=%lu bdi_limit=%lu task_limit=%lu "
- "task_weight=%ld%% task_gap=%ld%% bdi_gap=%ld%% "
- "pages_dirtied=%lu pause=%lu",
+ TP_printk("bdi %s: "
+ "bdi_limit=%lu task_limit=%lu bdi_dirty=%lu avg_dirty=%lu "
+ "bdi_gap=%ld%% task_gap=%ld%% task_weight=%ld%% "
+ "bdi_bw=%lu base_bw=%lu task_bw=%lu "
+ "dirtied=%lu period=%lu think=%ld pause=%ld",
__entry->bdi,
- __entry->bdi_dirty,
__entry->bdi_limit,
__entry->task_limit,
+ __entry->bdi_dirty,
+ __entry->avg_dirty,
+ BDP_PERCENT(bdi_limit, bdi_dirty, BDI_SOFT_DIRTY_LIMIT),
+ BDP_PERCENT(task_limit, avg_dirty, TASK_SOFT_DIRTY_LIMIT),
/* task weight: proportion of recent dirtied pages */
BDP_PERCENT(bdi_limit, task_limit, TASK_SOFT_DIRTY_LIMIT),
- BDP_PERCENT(task_limit, bdi_dirty, TASK_SOFT_DIRTY_LIMIT),
- BDP_PERCENT(bdi_limit, bdi_dirty, BDI_SOFT_DIRTY_LIMIT),
- __entry->pages_dirtied,
- __entry->pause
+ __entry->bdi_bw, /* bdi write bandwidth */
+ __entry->base_bw, /* bdi base throttle bandwidth */
+ __entry->task_bw, /* task throttle bandwidth */
+ __entry->dirtied,
+ __entry->period, /* ms */
+ __entry->think, /* ms */
+ __entry->pause /* ms */
)
);

--- linux-next.orig/mm/page-writeback.c 2010-12-09 12:24:47.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-12-09 12:24:49.000000000 +0800
@@ -785,6 +785,8 @@ static void balance_dirty_pages(struct a
pause_max = max_pause(bdi_thresh);

if (avg_dirty >= task_thresh || nr_dirty > dirty_thresh) {
+ bw = 0;
+ period = 0;
pause = pause_max;
goto pause;
}
@@ -812,6 +814,15 @@ static void balance_dirty_pages(struct a
* it may be a light dirtier.
*/
if (unlikely(-pause < HZ*10)) {
+ trace_balance_dirty_pages(bdi,
+ bdi_dirty,
+ avg_dirty,
+ bdi_thresh,
+ task_thresh,
+ pages_dirtied,
+ bw,
+ period,
+ pause);
if (-pause <= HZ/10)
current->paused_when += period;
else
@@ -824,9 +835,12 @@ static void balance_dirty_pages(struct a
pause:
trace_balance_dirty_pages(bdi,
bdi_dirty,
+ avg_dirty,
bdi_thresh,
task_thresh,
pages_dirtied,
+ bw,
+ period,
pause);
current->paused_when = jiffies;
__set_current_state(TASK_UNINTERRUPTIBLE);