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Date: Mon, 13 Apr 2009 14:55:58 +0900 (JST)
From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To: Zhaolei <zhaolei@...fujitsu.com>,
Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Tom Zanussi <tzanussi@...il.com>, Ingo Molnar <mingo@...e.hu>,
linux-kernel@...r.kernel.org
Cc: kosaki.motohiro@...fujitsu.com
Subject: [PATCH v2 4/4] ftrace: add latecy mesurement feature to workqueue tracer
Subject: [PATCH] ftrace: add latecy mesurement feature to workqueue tracer
The schedule_delayed_work() doesn't gurantee delay argument is exactly, of course.
but Administrator often wants to know how long time delayed it.
Then, this patch add latency mesurement feature to workqueue tracer.
<example output>
# cd /sys/kernel/debug/tracing/trace_stat
# cat workqueues
---------------------------------------------------------
# CPU INSERTED EXECUTED MAX_TIME MAX_LAT NAME
# | | | | | |
0 326 326 0.000115 2.421 events/0
0 0 0 0.000000 0.000 cpuset
0 597 597 0.000387 0.028 khelper
0 5 5 0.000029 0.002 kblockd/0
0 0 0 0.000000 0.000 kacpid
0 0 0 0.000000 0.000 kacpi_notify
0 0 0 0.000000 0.000 ksuspend_usbd
0 0 0 0.000000 0.000 aio/0
0 0 0 0.000000 0.000 crypto/0
0 0 0 0.000000 0.000 usbhid_resumer
0 299 299 0.004047 0.001 ata/0
0 0 0 0.000000 0.000 ata_aux
BTW, I'm not sure about why events/ workqueue thread always have long latency.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Zhaolei <zhaolei@...fujitsu.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Tom Zanussi <tzanussi@...il.com>
Cc: Ingo Molnar <mingo@...e.hu>
---
include/linux/workqueue.h | 3 +++
include/trace/workqueue_event_types.h | 10 ++++++++--
kernel/trace/trace_workqueue.c | 19 ++++++++++++++++---
kernel/workqueue.c | 18 +++++++++++++++++-
4 files changed, 44 insertions(+), 6 deletions(-)
Index: b/include/trace/workqueue_event_types.h
===================================================================
--- a/include/trace/workqueue_event_types.h 2009-04-13 13:58:21.000000000 +0900
+++ b/include/trace/workqueue_event_types.h 2009-04-13 14:07:14.000000000 +0900
@@ -43,6 +43,8 @@ TRACE_EVENT(workqueue_handler_entry,
__field(pid_t, thread_pid)
__field(struct work_struct *, work)
__field(work_func_t, func)
+ __field(unsigned long, expected_time)
+ __field(unsigned long, actual_time)
),
TP_fast_assign(
@@ -50,10 +52,14 @@ TRACE_EVENT(workqueue_handler_entry,
__entry->thread_pid = wq_thread->pid;
__entry->work = work;
__entry->func = work->func;
+ __entry->expected_time = work->expected_time;
+ __entry->actual_time = jiffies;
),
- TP_printk("thread=%s:%d func=%pF", __entry->thread_comm,
- __entry->thread_pid, __entry->func)
+ TP_printk("thread=%s:%d latency=%lums func=%pF", __entry->thread_comm,
+ __entry->thread_pid,
+ jiffies_to_msecs(__entry->actual_time-__entry->expected_time),
+ __entry->func)
);
TRACE_EVENT(workqueue_handler_exit,
Index: b/kernel/trace/trace_workqueue.c
===================================================================
--- a/kernel/trace/trace_workqueue.c 2009-04-13 13:59:51.000000000 +0900
+++ b/kernel/trace/trace_workqueue.c 2009-04-13 14:09:54.000000000 +0900
@@ -31,6 +31,9 @@ struct cpu_workqueue_stats {
/* store handler execution time */
u64 handler_start_time;
u64 max_executed_time;
+
+ /* store actual fired jiffies - caller expected jiffies */
+ unsigned long max_work_latency;
};
/* List of workqueue threads on one cpu */
@@ -80,8 +83,13 @@ probe_workqueue_entry(struct task_struct
list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
list) {
if (node->pid == wq_thread->pid) {
+ unsigned long latency;
+
node->executed++;
node->handler_start_time = trace_clock_global();
+ latency = jiffies - work->expected_time;
+ if (node->max_work_latency < latency)
+ node->max_work_latency = latency;
goto found;
}
}
@@ -226,6 +234,8 @@ static int workqueue_stat_show(struct se
unsigned long long exec_time = ns2usecs(cws->max_executed_time);
unsigned long exec_usec_rem = do_div(exec_time, USEC_PER_SEC);
unsigned long exec_secs = (unsigned long)exec_time;
+ unsigned long lat = jiffies_to_msecs(cws->max_work_latency);
+ unsigned long lat_msec_rem = do_div(lat, MSEC_PER_SEC);
spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
if (&cws->list == workqueue_cpu_stat(cpu)->list.next)
@@ -237,10 +247,11 @@ static int workqueue_stat_show(struct se
tsk = get_pid_task(pid, PIDTYPE_PID);
if (tsk) {
seq_printf(s, "%3d %6d %6u %5lu.%06lu"
- " %s\n",
+ " %5lu.%03lu %s\n",
cws->cpu,
atomic_read(&cws->inserted), cws->executed,
exec_secs, exec_usec_rem,
+ lat, lat_msec_rem,
tsk->comm);
put_task_struct(tsk);
}
@@ -252,8 +263,10 @@ static int workqueue_stat_show(struct se
static int workqueue_stat_headers(struct seq_file *s)
{
- seq_printf(s, "# CPU INSERTED EXECUTED MAX_TIME NAME\n");
- seq_printf(s, "# | | | | |\n");
+ seq_printf(s, "# CPU INSERTED EXECUTED MAX_TIME"
+ " MAX_LAT NAME\n");
+ seq_printf(s, "# | | | | "
+ " | |\n");
return 0;
}
Index: b/kernel/workqueue.c
===================================================================
--- a/kernel/workqueue.c 2009-04-13 13:58:21.000000000 +0900
+++ b/kernel/workqueue.c 2009-04-13 14:07:14.000000000 +0900
@@ -82,6 +82,20 @@ static const struct cpumask *cpu_singlet
*/
static cpumask_var_t cpu_populated_map __read_mostly;
+#ifdef CONFIG_WORKQUEUE_TRACER
+static void set_expected_time(struct work_struct *work,
+ unsigned long expected_jiffies)
+{
+ work->expected_time = expected_jiffies;
+}
+#else
+static void set_expected_time(struct work_struct *work,
+ unsigned long expected_jiffies)
+{
+}
+#endif
+
+
/* If it's single threaded, it isn't in the list of workqueues. */
static inline int is_wq_single_threaded(struct workqueue_struct *wq)
{
@@ -190,6 +204,7 @@ queue_work_on(int cpu, struct workqueue_
if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
BUG_ON(!list_empty(&work->entry));
+ set_expected_time(work, jiffies);
__queue_work(wq_per_cpu(wq, cpu), work);
ret = 1;
}
@@ -251,6 +266,7 @@ int queue_delayed_work_on(int cpu, struc
timer->expires = jiffies + delay;
timer->data = (unsigned long)dwork;
timer->function = delayed_work_timer_fn;
+ set_expected_time(&dwork->work, timer->expires);
if (unlikely(cpu >= 0))
add_timer_on(timer, cpu);
@@ -359,8 +375,8 @@ static void insert_wq_barrier(struct cpu
{
INIT_WORK(&barr->work, wq_barrier_func);
__set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
-
init_completion(&barr->done);
+ set_expected_time(&barr->work, jiffies);
insert_work(cwq, &barr->work, head);
}
Index: b/include/linux/workqueue.h
===================================================================
--- a/include/linux/workqueue.h 2009-04-13 12:04:48.000000000 +0900
+++ b/include/linux/workqueue.h 2009-04-13 14:11:06.000000000 +0900
@@ -32,6 +32,9 @@ struct work_struct {
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
+#ifdef CONFIG_WORKQUEUE_TRACER
+ unsigned long expected_time;
+#endif
};
#define WORK_DATA_INIT() ATOMIC_LONG_INIT(0)
--
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