writeback: trace event bdi_dirty_ratelimit

It helps understand how various throttle bandwidths are updated.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 178c235..ffb5deb 100644 (file)
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -226,6 +226,51 @@ TRACE_EVENT(global_dirty_state,
        )
 );
 
+#define KBps(x)                        ((x) << (PAGE_SHIFT - 10))
+
+TRACE_EVENT(bdi_dirty_ratelimit,
+
+       TP_PROTO(struct backing_dev_info *bdi,
+                unsigned long dirty_rate,
+                unsigned long task_ratelimit),
+
+       TP_ARGS(bdi, dirty_rate, task_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(bdi->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),

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0802d51..e3c2d8b 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -875,6 +875,8 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
 
        bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
        bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
+
+       trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit);
 }
 
 void __bdi_update_bandwidth(struct backing_dev_info *bdi,