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Date: Fri, 04 Nov 2011 22:24:46 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Jiri Olsa <jolsa@...hat.com>
Cc: fweisbec@...il.com, mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/latency: Fix header output for latency tracers
Sorry for the late reply, I'm still purging through my Inbox from over
the week in Prague.
On Tue, 2011-09-13 at 16:03 +0200, Jiri Olsa wrote:
> In case the the graph tracer (CONFIG_FUNCTION_GRAPH_TRACER) or even the
> function tracer (CONFIG_FUNCTION_TRACER) are not set, the latency tracers
> do not display proper latency header.
>
> The involved/fixed latency tracers are:
> wakeup_rt
> wakeup
> preemptirqsoff
> preemptoff
> irqsoff
>
> The patch adds proper handling of tracer configuration options for latency
> tracers, and displaying correct header info accordingly.
>
> * The current output (for wakeup tracer) with both graph and function
> tracers disabled is:
>
> # tracer: wakeup
> #
> cat-1163 0d..4 1us : 1163:120:R + [000] 6: 0:R migration/0
> cat-1163 0d..4 2us+: ttwu_do_activate.clone.1 <-try_to_wake_up
> cat-1163 0d..3 4us : __schedule <-preempt_schedule
> cat-1163 0d..3 4us : 1163:120:R ==> [000] 6: 0:R migration/0
>
>
> * The fixed output is:
>
> # tracer: wakeup
> #
> # wakeup latency trace v1.1.5 on 3.1.0-rc4-tip+
> # --------------------------------------------------------------------
> # latency: 91 us, #4/4, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
> # -----------------
> # | task: watchdog/0-7 (uid:0 nice:0 policy:1 rt_prio:99)
> # -----------------
> #
> <idle>-0 0d.h5 1us : 0:120:R + [000] 7: 0:R watchdog/0
> <idle>-0 0d.h5 2us+: ttwu_do_activate.clone.1 <-try_to_wake_up
> <idle>-0 0d..3 17us : __schedule <-schedule
> <idle>-0 0d..3 17us : 0:120:R ==> [000] 7: 0:R watchdog/0
Why the above header? Why not just use the latency header for all of
them?
-- Steve
>
>
> * There's slightly different output (for wakeup_rt tracer) when function
> tracer is enabled, currently:
>
> # tracer: wakeup_rt
> #
> cat-1168 1d..4 0us : 1168:120:R + [001] 8: 0:R migration/1
> cat-1168 1d..4 1us : ttwu_do_activate.clone.1 <-try_to_wake_up
> cat-1168 1d..3 1us : check_preempt_curr <-ttwu_do_wakeup
> ...
>
>
> * After the fix:
>
> # tracer: wakeup_rt
> #
> # wakeup_rt latency trace v1.1.5 on 3.1.0-rc4-tip+
> # --------------------------------------------------------------------
> # latency: 209 us, #113/113, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
> # -----------------
> # | task: watchdog/0-7 (uid:0 nice:0 policy:1 rt_prio:99)
> # -----------------
> #
> # _------=> CPU#
> # / _-----=> irqs-off
> # | / _----=> need-resched
> # || / _---=> hardirq/softirq
> # ||| / _--=> preempt-depth
> # |||| / delay
> # cmd pid ||||| time | caller
> # \ / ||||| \ | /
> cat-1168 1d..4 0us : 1168:120:R + [001] 8: 0:R migration/1
> cat-1168 1d..4 1us : ttwu_do_activate.clone.1 <-try_to_wake_up
> cat-1168 1d..3 1us : check_preempt_curr <-ttwu_do_wakeup
> ...
>
>
> Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> ---
> kernel/trace/trace.c | 12 ++++++++++++
> kernel/trace/trace.h | 1 +
> kernel/trace/trace_irqsoff.c | 13 ++++++++++++-
> kernel/trace/trace_sched_wakeup.c | 13 ++++++++++++-
> 4 files changed, 37 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index e5df02c..7086345 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2139,6 +2139,18 @@ enum print_line_t print_trace_line(struct trace_iterator *iter)
> return print_trace_fmt(iter);
> }
>
> +void trace_latency_header(struct seq_file *m)
> +{
> + struct trace_iterator *iter = m->private;
> +
> + /* print nothing if the buffers are empty */
> + if (trace_empty(iter))
> + return;
> +
> + if (iter->iter_flags & TRACE_FILE_LAT_FMT)
> + print_trace_header(m, iter);
> +}
> +
> void trace_default_header(struct seq_file *m)
> {
> struct trace_iterator *iter = m->private;
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 616846b..db40865 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -370,6 +370,7 @@ void trace_graph_function(struct trace_array *tr,
> unsigned long ip,
> unsigned long parent_ip,
> unsigned long flags, int pc);
> +void trace_latency_header(struct seq_file *m);
> void trace_default_header(struct seq_file *m);
> void print_trace_header(struct seq_file *m, struct trace_iterator *iter);
> int trace_empty(struct trace_iterator *iter);
> diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
> index 667aa8c..2a0aee6 100644
> --- a/kernel/trace/trace_irqsoff.c
> +++ b/kernel/trace/trace_irqsoff.c
> @@ -280,9 +280,20 @@ static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
> }
>
> static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
> -static void irqsoff_print_header(struct seq_file *s) { }
> static void irqsoff_trace_open(struct trace_iterator *iter) { }
> static void irqsoff_trace_close(struct trace_iterator *iter) { }
> +
> +#ifdef CONFIG_FUNCTION_TRACER
> +static void irqsoff_print_header(struct seq_file *s)
> +{
> + trace_default_header(s);
> +}
> +#else
> +static void irqsoff_print_header(struct seq_file *s)
> +{
> + trace_latency_header(s);
> +}
> +#endif /* CONFIG_FUNCTION_TRACER */
> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>
> /*
> diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
> index e4a70c0..ff791ea 100644
> --- a/kernel/trace/trace_sched_wakeup.c
> +++ b/kernel/trace/trace_sched_wakeup.c
> @@ -280,9 +280,20 @@ static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
> }
>
> static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
> -static void wakeup_print_header(struct seq_file *s) { }
> static void wakeup_trace_open(struct trace_iterator *iter) { }
> static void wakeup_trace_close(struct trace_iterator *iter) { }
> +
> +#ifdef CONFIG_FUNCTION_TRACER
> +static void wakeup_print_header(struct seq_file *s)
> +{
> + trace_default_header(s);
> +}
> +#else
> +static void wakeup_print_header(struct seq_file *s)
> +{
> + trace_latency_header(s);
> +}
> +#endif /* CONFIG_FUNCTION_TRACER */
> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>
> /*
--
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