Re: Re: [RFC PATCH] Add timer-source of walltime for ftrace

Zhaolei
2009-08-18T02:06:29Z

Frederic Weisbecker wrote:
> On Mon, Aug 17, 2009 at 05:22:04PM +0800, Zhaolei wrote:
>> We can add a timer-source for ftrace to support wall-time display.
>> It is based on Steven Rostedt <rostedt@goodmis.org>'s suggestion in:
>> http://lkml.org/lkml/2009/7/24/103
>>
>> It needs to be applied on my patch of:
>> [PATCH v4 1/2] Add function to convert between calendar time and broken-down time for universal use
>> and
>> [PATCH v2 2/2] ftrace: Unify effect of writing to trace_options and option/*
>>
>> We can get following output:
>> # cd /mnt/debugfs/tracing/
>> # ls options/*clock
>> options/global-clock options/local-clock options/walltime-clock
>> # echo sched_switch > current_tracer
>> # cat trace
>> # tracer: sched_switch
>> #
>> # TASK-PID CPU# TIMESTAMP FUNCTION
>> # | | | | |
>> bash-3560 [000] 694.242386: 3560:120:S + [000] 3560:120:S bash
>> bash-3560 [000] 694.242476: 3560:120:S + [000] 3560:120:S bash
>> bash-3560 [000] 694.242865: 3560:120:R + [000] 5:115:S events/0
>> bash-3560 [000] 694.242912: 3560:120:R ==> [000] 5:115:R events/0
>> events/0-5 [000] 694.243015: 5:115:R + [000] 3558:120:S sshd
>> events/0-5 [000] 694.243040: 5:115:S ==> [000] 3560:120:R bash
>> bash-3560 [000] 694.243312: 3560:120:S + [000] 3560:120:S bash
>> bash-3560 [000] 694.243374: 3560:120:S ==> [000] 3558:120:R sshd
>> ...
>> # echo 1 > options/walltime-clock
>> # echo > trace
>> # cat trace
>> # tracer: sched_switch
>> #
>> # TASK-PID CPU# TIMESTAMP FUNCTION
>> # | | | | |
>> bash-3560 [000] 2009-08-17 23:58:22 3560:120:S + [000] 3560:120:S bash
>> bash-3560 [000] 2009-08-17 23:58:22 3560:120:R + [000] 5:115:S events/0
>> bash-3560 [000] 2009-08-17 23:58:22 3560:120:R ==> [000] 5:115:R events/0
>> events/0-5 [000] 2009-08-17 23:58:22 5:115:R + [000] 3558:120:S sshd
>> events/0-5 [000] 2009-08-17 23:58:22 5:115:S ==> [000] 3558:120:R sshd
>> sshd-3558 [000] 2009-08-17 23:58:22 3558:120:S ==> [000] 3560:120:R bash
>> bash-3560 [000] 2009-08-17 23:58:22 3560:120:S + [000] 3560:120:S bash
>> bash-3560 [000] 2009-08-17 23:58:22 3560:120:S + [000] 3560:120:S bash
>> ...
>>
>> Note:
>> It is only a prototype patch to for demostrate what is result looks like.
>> There still have many works to do(bug to fix) before apply.
>> For example, we need to add a hook(tracepoint) of xtime change event,
>> so we can update walltime's clock base then.
>> And maybe we need clear all events when changing clock-source, because old
>> clock value can't displayed correctly in new clock's format.
>>
>> Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
>> ---
>> include/linux/trace_clock.h | 1 +
>> kernel/trace/trace.c | 55 ++++++++++++++++++++++++++++++------------
>> kernel/trace/trace.h | 6 +++-
>> kernel/trace/trace_clock.c | 47 ++++++++++++++++++++++++++++++++++++
>> kernel/trace/trace_output.c | 20 ++++++++++++---
>> 5 files changed, 107 insertions(+), 22 deletions(-)
>>
>> diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h
>> index 7a81303..322707e 100644
>> --- a/include/linux/trace_clock.h
>> +++ b/include/linux/trace_clock.h
>> @@ -15,5 +15,6 @@
>> extern u64 notrace trace_clock_local(void);
>> extern u64 notrace trace_clock(void);
>> extern u64 notrace trace_clock_global(void);
>> +extern u64 notrace trace_clock_walltime(void);
>>
>> #endif /* _LINUX_TRACE_CLOCK_H */
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index b7d873b..4474f7d 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -263,8 +263,8 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);
>>
>> /* trace_flags holds trace_options default values */
>> unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
>> - TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
>> - TRACE_ITER_GRAPH_TIME;
>> + TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_LOCAL_CLK |
>> + TRACE_ITER_SLEEP_TIME | TRACE_ITER_GRAPH_TIME;
>>
>> /**
>> * trace_wake_up - wake up tasks waiting for trace input
>> @@ -324,6 +324,8 @@ static const char *trace_options[] = {
>> "context-info",
>> "latency-format",
>> "global-clock",
>> + "local-clock",
>> + "walltime-clock",
>> "sleep-time",
>> "graph-time",
>> NULL
>> @@ -1423,8 +1425,17 @@ static void print_lat_help_header(struct seq_file *m)
>>
>> static void print_func_help_header(struct seq_file *m)
>> {
>> - seq_puts(m, "# TASK-PID CPU# TIMESTAMP FUNCTION\n");
>> - seq_puts(m, "# | | | | |\n");
>> + if (trace_flags & TRACE_ITER_WALLTIME_CLK) {
>> + seq_puts(m, "# TASK-PID CPU# "
>> + " TIMESTAMP FUNCTION\n");
>> + seq_puts(m, "# | | | "
>> + " | |\n");
>> + } else {
>> + seq_puts(m, "# TASK-PID CPU# "
>> + " TIMESTAMP FUNCTION\n");
>> + seq_puts(m, "# | | | "
>> + " | |\n");
>> + }
>> }
>>
>>
>> @@ -2151,30 +2162,42 @@ static int set_tracer_option(struct tracer *trace, char *cmp, int neg)
>>
>> static void set_tracer_flags(unsigned int mask, int enabled)
>> {
>> + u64 (*clkfunc)(void) = NULL;
>> +
>> /* do nothing if flag is already set */
>> if (!!(trace_flags & mask) == !!enabled)
>> return;
>>
>> - if (enabled)
>> - trace_flags |= mask;
>> - else
>> - trace_flags &= ~mask;
>> + if (mask == TRACE_ITER_GLOBAL_CLK)
>> + clkfunc = trace_clock_global;
>> + if (mask == TRACE_ITER_LOCAL_CLK)
>> + clkfunc = trace_clock_local;
>> + if (mask == TRACE_ITER_WALLTIME_CLK)
>> + clkfunc = trace_clock_walltime;
>>
>> - if (mask == TRACE_ITER_GLOBAL_CLK) {
>> - u64 (*func)(void);
>> + if (clkfunc) {
>> + if (!enabled)
>> + return;
>
>
>
> If the user set a clock option file to 0, then it means he
> was expecting something, probably reset the default clock
> which is clock_local.

Agree.

> But what if the user set 0 to the local_clock...hmm..

or make option like:
# echo wallclock > option/clock
# echo localclock > option/clock
is best way.
But it needs rewriting whole option source.

Maybe now, we can use a neutrality way as:
# echo 0 > option/wallclock # reset to default clock(local clock)
# echo 0 > option/locakclock # no effect

Thanks
Zhaolei