Hi all:
This is to solve the bug message shown in perf sched latency.
# perf sched latency|tail
ksoftirqd/0:3 | 0.597 ms | 57 | avg: 0.004 ms |
max: 0.054 ms | max at: 19681.546204 s
ksoftirqd/1:14 | 0.637 ms | 58 | avg: 0.004 ms |
max: 0.066 ms | max at: 19674.687734 s
irqbalance:349 | 0.429 ms | 1 | avg: 0.004 ms |
max: 0.004 ms | max at: 19675.791528 s
ksoftirqd/3:24 | 0.527 ms | 67 | avg: 0.003 ms |
max: 0.011 ms | max at: 19673.285019 s
migration/3:23 | 0.000 ms | 1 | avg: 0.002 ms |
max: 0.002 ms | max at: 19672.055354 s
-----------------------------------------------------------------------------------------
TOTAL: | 4384.616 ms | 36879 |
---------------------------------------------------
INFO: 0.030% state machine bugs (11 out of 36684)
After some investigation, there are two reasons cause this problem.
(1). Sometimes, scheduler will wake up a running task, it is not
necessary,
then I skip the wakeup if task->state is TASK_RUNNING. [4/8]
(2). No tracing for sched wait.
This is a simple graph for task state changing.
---------------- 1 ----------------
| TASK_RUNNING | ------------------------------>| TASK_RUNNING |
| (running) |<------------------------------ | (wait cpu) |
---------------- 2 ----------------
^ |
|4 ------------------------- 3 |
|-------|TASK_{UN}INTERRUPTABLE |<--------------|
| in wait_rq |
-------------------------
As the graph shown above, there are four event in scheduling, and
we currently are tracing 3 of them.
1 & 2: sched:sched_switch
4: sched:sched_wakeup|sched:sched_wakeup_new
But about 3, we have no trace event for it.
This patchset add a new trace event for sched wait, and add a trace point
before any task added into wait queue. [1/8] & [3/8]
BTW, other patchs in this thread are about some little fix and
enhancement
in the development, please help to review at the same time.
Thanx
Dongsheng (8):
sched & trace: Add a trace event for wait.
sched/wait: Add trace point before add task into wait queue.
sched/wait: Use __add_wait_queue{_tail}_exclusive() as possible.
sched/core: Skip wakeup when task is already running.
perf tools: record and process sched:sched_wait event.
perf tools: add missing event for perf sched record.
perf tools: Adapt the TASK_STATE_TO_CHAR_STR to new value in kernel
space.
perf tools: Clarify the output of perf sched map.
include/trace/events/sched.h | 20 +++++++++
kernel/sched/core.c | 3 ++
kernel/sched/wait.c | 13 ++++--
tools/perf/builtin-sched.c | 100 +++++++++++++++++++++++++++++++++++--------
4 files changed, 115 insertions(+), 21 deletions(-)
--
1.8.2.1
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