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Subject[PATCH 08/18] writeback: trace dirty_ratelimit
It helps understand how various throttle bandwidths are updated.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
include/trace/events/writeback.h | 46 +++++++++++++++++++++++++++++
mm/page-writeback.c | 3 +
2 files changed, 49 insertions(+)
--- linux-next.orig/mm/page-writeback.c 2011-08-29 19:51:30.000000000 +0800
+++ linux-next/mm/page-writeback.c 2011-08-29 19:52:11.000000000 +0800
@@ -864,6 +864,9 @@ static void bdi_update_dirty_ratelimit(s
dirty_ratelimit -= step;

bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
+
+ trace_dirty_ratelimit(bdi, dirty_rate, task_ratelimit,
+ balanced_dirty_ratelimit);
}

void __bdi_update_bandwidth(struct backing_dev_info *bdi,
--- linux-next.orig/include/trace/events/writeback.h 2011-08-29 19:51:30.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2011-08-29 19:52:11.000000000 +0800
@@ -226,6 +226,52 @@ TRACE_EVENT(global_dirty_state,
)
);

+#define KBps(x) ((x) << (PAGE_SHIFT - 10))
+
+TRACE_EVENT(dirty_ratelimit,
+
+ TP_PROTO(struct backing_dev_info *bdi,
+ unsigned long dirty_rate,
+ unsigned long task_ratelimit,
+ unsigned long balanced_dirty_ratelimit),
+
+ TP_ARGS(bdi, dirty_rate, task_ratelimit, balanced_dirty_ratelimit),
+
+ TP_STRUCT__entry(
+ __array(char, bdi, 32)
+ __field(unsigned long, write_bw)
+ __field(unsigned long, avg_write_bw)
+ __field(unsigned long, dirty_rate)
+ __field(unsigned long, dirty_ratelimit)
+ __field(unsigned long, task_ratelimit)
+ __field(unsigned long, balanced_dirty_ratelimit)
+ ),
+
+ TP_fast_assign(
+ strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
+ __entry->write_bw = KBps(bdi->write_bandwidth);
+ __entry->avg_write_bw = KBps(bdi->avg_write_bandwidth);
+ __entry->dirty_rate = KBps(dirty_rate);
+ __entry->dirty_ratelimit = KBps(bdi->dirty_ratelimit);
+ __entry->task_ratelimit = KBps(task_ratelimit);
+ __entry->balanced_dirty_ratelimit =
+ KBps(balanced_dirty_ratelimit);
+ ),
+
+ TP_printk("bdi %s: "
+ "write_bw=%lu awrite_bw=%lu dirty_rate=%lu "
+ "dirty_ratelimit=%lu task_ratelimit=%lu "
+ "balanced_dirty_ratelimit=%lu",
+ __entry->bdi,
+ __entry->write_bw, /* write bandwidth */
+ __entry->avg_write_bw, /* avg write bandwidth */
+ __entry->dirty_rate, /* bdi dirty rate */
+ __entry->dirty_ratelimit, /* base ratelimit */
+ __entry->task_ratelimit, /* ratelimit with position control */
+ __entry->balanced_dirty_ratelimit /* the balanced ratelimit */
+ )
+);
+
DECLARE_EVENT_CLASS(writeback_congest_waited_template,

TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),



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