From 83712358ba0a1497ce59a4f84ce4dd0f803fe6fc Mon Sep 17 00:00:00 2001 From: Wu Fengguang Date: Sat, 11 Jun 2011 19:25:42 -0600 Subject: writeback: dirty ratelimit - think time compensation Compensate the task's think time when computing the final pause time, so that ->dirty_ratelimit can be executed accurately. think time := time spend outside of balance_dirty_pages() In the rare case that the task slept longer than the 200ms period time (result in negative pause time), the sleep time will be compensated in the following periods, too, if it's less than 1 second. Accumulated errors are carefully avoided as long as the max pause area is not hitted. Pseudo code: period = pages_dirtied / task_ratelimit; think = jiffies - dirty_paused_when; pause = period - think; 1) normal case: period > think pause = period - think dirty_paused_when = jiffies + pause nr_dirtied = 0 period time |===============================>| think time pause time |===============>|==============>| ------|----------------|---------------|------------------------ dirty_paused_when jiffies 2) no pause case: period <= think don't pause; reduce future pause time by: dirty_paused_when += period nr_dirtied = 0 period time |===============================>| think time |===================================================>| ------|--------------------------------+-------------------|---- dirty_paused_when jiffies Acked-by: Jan Kara Acked-by: Peter Zijlstra Signed-off-by: Wu Fengguang --- include/trace/events/writeback.h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'include/trace') diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index 99d1d0decf8..8588a891802 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -300,12 +300,13 @@ TRACE_EVENT(balance_dirty_pages, unsigned long dirty_ratelimit, unsigned long task_ratelimit, unsigned long dirtied, + unsigned long period, 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), + dirtied, period, pause, start_time), TP_STRUCT__entry( __array( char, bdi, 32) @@ -320,6 +321,8 @@ TRACE_EVENT(balance_dirty_pages, __field(unsigned int, dirtied_pause) __field(unsigned long, paused) __field( long, pause) + __field(unsigned long, period) + __field( long, think) ), TP_fast_assign( @@ -336,6 +339,9 @@ TRACE_EVENT(balance_dirty_pages, __entry->task_ratelimit = KBps(task_ratelimit); __entry->dirtied = dirtied; __entry->dirtied_pause = current->nr_dirtied_pause; + __entry->think = current->dirty_paused_when == 0 ? 0 : + (long)(jiffies - current->dirty_paused_when) * 1000/HZ; + __entry->period = period * 1000 / HZ; __entry->pause = pause * 1000 / HZ; __entry->paused = (jiffies - start_time) * 1000 / HZ; ), @@ -346,7 +352,7 @@ TRACE_EVENT(balance_dirty_pages, "bdi_setpoint=%lu bdi_dirty=%lu " "dirty_ratelimit=%lu task_ratelimit=%lu " "dirtied=%u dirtied_pause=%u " - "paused=%lu pause=%ld", + "paused=%lu pause=%ld period=%lu think=%ld", __entry->bdi, __entry->limit, __entry->setpoint, @@ -358,7 +364,9 @@ TRACE_EVENT(balance_dirty_pages, __entry->dirtied, __entry->dirtied_pause, __entry->paused, /* ms */ - __entry->pause /* ms */ + __entry->pause, /* ms */ + __entry->period, /* ms */ + __entry->think /* ms */ ) ); -- cgit v1.2.3