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

Frederic Weisbecker
2009-08-17T16:49:16Z

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.

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