[PATCH v4 0/3] tracing: signaling large duration and delay

[PATCH v4 0/3] tracing: signaling large duration and delay

[byungchul.park]

From: Byungchul Park <byungchul.park@lge.com>

Changes since v3
* re-position define macro and undef explicitly
* enhance readablity

Changes since v2
* use inline function instead of macro
* enhance readablity

Changes since v1
* update Document/trace/ftrace.txt
* seperate the implementation as a macro
* apply the implementation to delay printing, too

Hello.

When I analysis the exit_mm() function to find out the reason why the
function spends much time occasionally, this patch was very useful.
I thought this patch cannot be useful only for me, but can be also
useful for anybody who want to be signaled for very large function
execution time, so I decided to submit this patchset.

Nobody who have such a demand? :)

Thanks,
Byungchul.

Byungchul Park (3):
  tracing, function_graph: fix micro seconds notation in comment
  tracing, function_graph: add additional marks to signal very large
    function execution time
  tracing: add additional marks to signal very large delay

 Documentation/trace/ftrace.txt       |   10 +++++++---
 kernel/trace/trace.h                 |   21 +++++++++++++++++++++
 kernel/trace/trace_functions_graph.c |   31 +++++++++++++++++++++----------
 kernel/trace/trace_output.c          |   23 ++++++++++++++++++-----
 4 files changed, 67 insertions(+), 18 deletions(-)

-- 
1.7.9.5

[PATCH v4 1/3] tracing, function_graph: fix micro seconds notation in comment

[byungchul.park]

From: Byungchul Park <byungchul.park@lge.com>

Usually, "msecs" notation means milli-seconds, and "usecs" notation
means micro-seconds. Since the unit used in the code is micro-seconds,
the notation should be replaced from msecs to usecs.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 kernel/trace/trace_functions_graph.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index f0a0c98..cb33f46 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -759,19 +759,19 @@ trace_print_graph_duration(unsigned long long duration, struct trace_seq *s)
 {
 	unsigned long nsecs_rem = do_div(duration, 1000);
 	/* log10(ULONG_MAX) + '\0' */
-	char msecs_str[21];
+	char usecs_str[21];
 	char nsecs_str[5];
 	int ret, len;
 	int i;
 
-	sprintf(msecs_str, "%lu", (unsigned long) duration);
+	sprintf(usecs_str, "%lu", (unsigned long) duration);
 
 	/* Print msecs */
-	ret = trace_seq_printf(s, "%s", msecs_str);
+	ret = trace_seq_printf(s, "%s", usecs_str);
 	if (!ret)
 		return TRACE_TYPE_PARTIAL_LINE;
 
-	len = strlen(msecs_str);
+	len = strlen(usecs_str);
 
 	/* Print nsecs (we don't want to exceed 7 numbers) */
 	if (len < 7) {
@@ -822,10 +822,10 @@ print_graph_duration(unsigned long long duration, struct trace_seq *s,
 
 	/* Signal a overhead of time execution to the output */
 	if (flags & TRACE_GRAPH_PRINT_OVERHEAD) {
-		/* Duration exceeded 100 msecs */
+		/* Duration exceeded 100 usecs */
 		if (duration > 100000ULL)
 			ret = trace_seq_puts(s, "! ");
-		/* Duration exceeded 10 msecs */
+		/* Duration exceeded 10 usecs */
 		else if (duration > 10000ULL)
 			ret = trace_seq_puts(s, "+ ");
 	}
-- 
1.7.9.5

[PATCH v4 2/3] tracing, function_graph: add additional marks to signal very large function execution time

[byungchul.park]

From: Byungchul Park <byungchul.park@lge.com>

Currently, function graph tracer prints "!" or "+" just before
function execution time to signal a function overhead, depending
on the time. Even it is usually enough to do that, we sometimes
need to be signaled for bigger execution time than 100 micro seconds.

For example, I used function graph tracer to detect if there is
any case that exit_mm() takes too much time. I did following steps
in /sys/kernel/debug/tracing. It was easier to detect very big
excution time with patched kernel than with original kernel.

$ echo exit_mm > set_graph_function
$ echo function_graph > current_tracer
$ echo > trace
$ cat trace_pipe > $LOGFILE
 ... (do something and terminate logging)
$ grep "\\$" $LOGFILE
 3) $ 22082032 us |                      } /* kernel_map_pages */
 3) $ 22082040 us |                    } /* free_pages_prepare */
 3) $ 22082113 us |                  } /* free_hot_cold_page */
 3) $ 22083455 us |                } /* free_hot_cold_page_list */
 3) $ 22083895 us |              } /* release_pages */
 3) $ 22177873 us |            } /* free_pages_and_swap_cache */
 3) $ 22178929 us |          } /* unmap_single_vma */
 3) $ 22198885 us |        } /* unmap_vmas */
 3) $ 22206949 us |      } /* exit_mmap */
 3) $ 22207659 us |    } /* mmput */
 3) $ 22207793 us |  } /* exit_mm */

And then, it was easy to find out that a schedule-out occured by
sub_preempt_count() within kernel_map_pages().

To detect very large function exection time caused by either problematic
function implementation or scheduling issues, this patch can be useful.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 Documentation/trace/ftrace.txt       |    2 ++
 kernel/trace/trace.h                 |   21 +++++++++++++++++++++
 kernel/trace/trace_functions_graph.c |   23 +++++++++++++++++------
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 4da4261..f827e2f 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1951,6 +1951,8 @@ want, depending on your needs.
 
   + means that the function exceeded 10 usecs.
   ! means that the function exceeded 100 usecs.
+  # means that the function exceeded 1000 usecs.
+  $ means that the function exceeded 1 sec.
 
 
 - The task/pid field displays the thread cmdline and pid which
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 385391f..49ce26c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -331,6 +331,27 @@ struct tracer_flags {
 /* Makes more easy to define a tracer opt */
 #define TRACER_OPT(s, b)	.name = #s, .bit = b
 
+/* trace overhead mark */
+struct trace_mark {
+	unsigned long long	val; /* unit: nsec */
+	char			sym;
+};
+
+static inline char trace_duration_mark(unsigned long long d,
+				       const struct trace_mark m[],
+				       int size)
+{
+	int i;
+
+	if (size <= 0) return ' ';
+
+	for (i = 0; i < size; i++) {
+		if (d >= m[i].val)
+			break;
+	}
+
+	return (i == size)? ' ' : m[i].sym;
+}
 
 /**
  * struct tracer - a specific tracer and its callbacks to interact with debugfs
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index cb33f46..c187c4a 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -797,6 +797,22 @@ trace_print_graph_duration(unsigned long long duration, struct trace_seq *s)
 	return TRACE_TYPE_HANDLED;
 }
 
+#undef MARK
+#define MARK(v, s) {.val = v, .sym = s}
+static const struct trace_mark mark[] = {
+	MARK(1000000000ULL	, '$'), /* 1 sec */
+	MARK(1000000ULL		, '#'), /* 1000 usecs */
+	MARK(100000ULL		, '!'), /* 100 usecs */
+	MARK(10000ULL		, '+'), /* 10 usecs */
+	MARK(0ULL		, ' '), /* 0 usecs */
+};
+#undef MARK
+
+static inline char find_trace_mark(unsigned long long d)
+{
+	return trace_duration_mark(d, mark, ARRAY_SIZE(mark));
+}
+
 static enum print_line_t
 print_graph_duration(unsigned long long duration, struct trace_seq *s,
 		     u32 flags)
@@ -822,12 +838,7 @@ print_graph_duration(unsigned long long duration, struct trace_seq *s,
 
 	/* Signal a overhead of time execution to the output */
 	if (flags & TRACE_GRAPH_PRINT_OVERHEAD) {
-		/* Duration exceeded 100 usecs */
-		if (duration > 100000ULL)
-			ret = trace_seq_puts(s, "! ");
-		/* Duration exceeded 10 usecs */
-		else if (duration > 10000ULL)
-			ret = trace_seq_puts(s, "+ ");
+		ret = trace_seq_printf(s, "%c ", find_trace_mark(duration));
 	}
 
 	/*
-- 
1.7.9.5

[PATCH v4 3/3] tracing: add additional marks to signal very large delay

[byungchul.park]

From: Byungchul Park <byungchul.park@lge.com>

Currently, some tracers tracing latency print "!" or "+" just after time
to signal overhead, depending on the interval between events. Even it is
usually enough to do that, we sometimes need to be signaled for bigger
interval than 100 micro seconds.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 Documentation/trace/ftrace.txt |    8 +++++---
 kernel/trace/trace_output.c    |   23 ++++++++++++++++++-----
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index f827e2f..64efb3e 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -680,9 +680,11 @@ The above is mostly meaningful for kernel developers.
 	 needs to be fixed to be only relative to the same CPU.
 	 The marks are determined by the difference between this
 	 current trace and the next trace.
-	  '!' - greater than preempt_mark_thresh (default 100)
-	  '+' - greater than 1 microsecond
-	  ' ' - less than or equal to 1 microsecond.
+	  '$' - greater than 1 second
+	  '#' - greater than 1000 microsecond
+	  '!' - greater than 100 microsecond
+	  '+' - greater than 10 microsecond
+	  ' ' - less than or equal to 10 microsecond.
 
   The rest is the same as the 'trace' file.
 
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index c6977d5..3fd3017 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -124,7 +124,7 @@ ftrace_print_symbols_seq(struct trace_seq *p, unsigned long val,
 
 	if (ret == (const char *)(trace_seq_buffer_ptr(p)))
 		trace_seq_printf(p, "0x%lx", val);
-		
+
 	trace_seq_putc(p, 0);
 
 	return ret;
@@ -471,7 +471,21 @@ lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
 	return trace_print_lat_fmt(s, entry);
 }
 
-static unsigned long preempt_mark_thresh_us = 100;
+#undef MARK
+#define MARK(v, s) {.val = v, .sym = s}
+static const struct trace_mark mark[] = {
+	MARK(1000000000ULL	, '$'), /* 1 sec */
+	MARK(1000000ULL		, '#'), /* 1000 usecs */
+	MARK(100000ULL		, '!'), /* 100 usecs */
+	MARK(10000ULL		, '+'), /* 10 usecs */
+	MARK(0ULL		, ' '), /* 0 usecs */
+};
+#undef MARK
+
+static inline char find_trace_mark(unsigned long long d)
+{
+	return trace_duration_mark(d, mark, ARRAY_SIZE(mark));
+}
 
 static int
 lat_print_timestamp(struct trace_iterator *iter, u64 next_ts)
@@ -506,8 +520,7 @@ lat_print_timestamp(struct trace_iterator *iter, u64 next_ts)
 		return trace_seq_printf(
 				s, " %4lldus%c: ",
 				abs_ts,
-				rel_ts > preempt_mark_thresh_us ? '!' :
-				  rel_ts > 1 ? '+' : ' ');
+				find_trace_mark(rel_ts * NSEC_PER_USEC));
 	} else { /* !verbose && !in_ns */
 		return trace_seq_printf(s, " %4lld: ", abs_ts);
 	}
@@ -692,7 +705,7 @@ int register_ftrace_event(struct trace_event *event)
 				goto out;
 
 		} else {
-			
+
 			event->type = next_event_type++;
 			list = &ftrace_event_list;
 		}
-- 
1.7.9.5

Re: [PATCH v4 3/3] tracing: add additional marks to signal very large delay

[Steven Rostedt]

On Tue, 18 Nov 2014 14:57:26 +0900
byungchul.park@lge.com wrote:

> From: Byungchul Park <byungchul.park@lge.com>
> 
> Currently, some tracers tracing latency print "!" or "+" just after time
> to signal overhead, depending on the interval between events. Even it is
> usually enough to do that, we sometimes need to be signaled for bigger
> interval than 100 micro seconds.
> 
> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> ---
>  Documentation/trace/ftrace.txt |    8 +++++---
>  kernel/trace/trace_output.c    |   23 ++++++++++++++++++-----
>  2 files changed, 23 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
> index f827e2f..64efb3e 100644
> --- a/Documentation/trace/ftrace.txt
> +++ b/Documentation/trace/ftrace.txt
> @@ -680,9 +680,11 @@ The above is mostly meaningful for kernel developers.
>  	 needs to be fixed to be only relative to the same CPU.
>  	 The marks are determined by the difference between this
>  	 current trace and the next trace.
> -	  '!' - greater than preempt_mark_thresh (default 100)
> -	  '+' - greater than 1 microsecond
> -	  ' ' - less than or equal to 1 microsecond.
> +	  '$' - greater than 1 second
> +	  '#' - greater than 1000 microsecond
> +	  '!' - greater than 100 microsecond
> +	  '+' - greater than 10 microsecond
> +	  ' ' - less than or equal to 10 microsecond.
>  
>    The rest is the same as the 'trace' file.
>  
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index c6977d5..3fd3017 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -124,7 +124,7 @@ ftrace_print_symbols_seq(struct trace_seq *p, unsigned long val,
>  
>  	if (ret == (const char *)(trace_seq_buffer_ptr(p)))
>  		trace_seq_printf(p, "0x%lx", val);
> -		
> +
>  	trace_seq_putc(p, 0);
>  
>  	return ret;
> @@ -471,7 +471,21 @@ lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
>  	return trace_print_lat_fmt(s, entry);
>  }
>  
> -static unsigned long preempt_mark_thresh_us = 100;
> +#undef MARK
> +#define MARK(v, s) {.val = v, .sym = s}
> +static const struct trace_mark mark[] = {
> +	MARK(1000000000ULL	, '$'), /* 1 sec */
> +	MARK(1000000ULL		, '#'), /* 1000 usecs */
> +	MARK(100000ULL		, '!'), /* 100 usecs */
> +	MARK(10000ULL		, '+'), /* 10 usecs */
> +	MARK(0ULL		, ' '), /* 0 usecs */
> +};
> +#undef MARK
> +
> +static inline char find_trace_mark(unsigned long long d)
> +{
> +	return trace_duration_mark(d, mark, ARRAY_SIZE(mark));
> +}

This is the exact same code as in function_graph tracer. Nuke the one
from function graph and make this one a non static function, and have
function graph tracer use it. trace_output.c is always compiled with
tracing.

In fact, remove all the code from trace.h, and move it here. Just
have this function be global and rename it to:

 trace_find_mark()

-- Steve


>  
>  static int
>  lat_print_timestamp(struct trace_iterator *iter, u64 next_ts)
> @@ -506,8 +520,7 @@ lat_print_timestamp(struct trace_iterator *iter, u64 next_ts)
>  		return trace_seq_printf(
>  				s, " %4lldus%c: ",
>  				abs_ts,
> -				rel_ts > preempt_mark_thresh_us ? '!' :
> -				  rel_ts > 1 ? '+' : ' ');
> +				find_trace_mark(rel_ts * NSEC_PER_USEC));
>  	} else { /* !verbose && !in_ns */
>  		return trace_seq_printf(s, " %4lld: ", abs_ts);
>  	}
> @@ -692,7 +705,7 @@ int register_ftrace_event(struct trace_event *event)
>  				goto out;
>  
>  		} else {
> -			
> +
>  			event->type = next_event_type++;
>  			list = &ftrace_event_list;
>  		}

Re: [PATCH v4 3/3] tracing: add additional marks to signal very large delay

[Byungchul Park]

On Wed, Nov 19, 2014 at 01:35:15PM -0500, Steven Rostedt wrote:
> On Tue, 18 Nov 2014 14:57:26 +0900
> byungchul.park@lge.com wrote:
> 
> > From: Byungchul Park <byungchul.park@lge.com>
> > 
> > Currently, some tracers tracing latency print "!" or "+" just after time
> > to signal overhead, depending on the interval between events. Even it is
> > usually enough to do that, we sometimes need to be signaled for bigger
> > interval than 100 micro seconds.
> > 
> > Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> > ---
> >  Documentation/trace/ftrace.txt |    8 +++++---
> >  kernel/trace/trace_output.c    |   23 ++++++++++++++++++-----
> >  2 files changed, 23 insertions(+), 8 deletions(-)
> > 
> > diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
> > index f827e2f..64efb3e 100644
> > --- a/Documentation/trace/ftrace.txt
> > +++ b/Documentation/trace/ftrace.txt
> > @@ -680,9 +680,11 @@ The above is mostly meaningful for kernel developers.
> >  	 needs to be fixed to be only relative to the same CPU.
> >  	 The marks are determined by the difference between this
> >  	 current trace and the next trace.
> > -	  '!' - greater than preempt_mark_thresh (default 100)
> > -	  '+' - greater than 1 microsecond
> > -	  ' ' - less than or equal to 1 microsecond.
> > +	  '$' - greater than 1 second
> > +	  '#' - greater than 1000 microsecond
> > +	  '!' - greater than 100 microsecond
> > +	  '+' - greater than 10 microsecond
> > +	  ' ' - less than or equal to 10 microsecond.
> >  
> >    The rest is the same as the 'trace' file.
> >  
> > diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> > index c6977d5..3fd3017 100644
> > --- a/kernel/trace/trace_output.c
> > +++ b/kernel/trace/trace_output.c
> > @@ -124,7 +124,7 @@ ftrace_print_symbols_seq(struct trace_seq *p, unsigned long val,
> >  
> >  	if (ret == (const char *)(trace_seq_buffer_ptr(p)))
> >  		trace_seq_printf(p, "0x%lx", val);
> > -		
> > +
> >  	trace_seq_putc(p, 0);
> >  
> >  	return ret;
> > @@ -471,7 +471,21 @@ lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
> >  	return trace_print_lat_fmt(s, entry);
> >  }
> >  
> > -static unsigned long preempt_mark_thresh_us = 100;
> > +#undef MARK
> > +#define MARK(v, s) {.val = v, .sym = s}
> > +static const struct trace_mark mark[] = {
> > +	MARK(1000000000ULL	, '$'), /* 1 sec */
> > +	MARK(1000000ULL		, '#'), /* 1000 usecs */
> > +	MARK(100000ULL		, '!'), /* 100 usecs */
> > +	MARK(10000ULL		, '+'), /* 10 usecs */
> > +	MARK(0ULL		, ' '), /* 0 usecs */
> > +};
> > +#undef MARK
> > +
> > +static inline char find_trace_mark(unsigned long long d)
> > +{
> > +	return trace_duration_mark(d, mark, ARRAY_SIZE(mark));
> > +}
> 
> This is the exact same code as in function_graph tracer. Nuke the one
> from function graph and make this one a non static function, and have
> function graph tracer use it. trace_output.c is always compiled with
> tracing.
> 
> In fact, remove all the code from trace.h, and move it here. Just
> have this function be global and rename it to:
> 
>  trace_find_mark()
> 
> -- Steve

OK. I will do that.

Thank you,
BYungchul

> 
> 
> >  
> >  static int
> >  lat_print_timestamp(struct trace_iterator *iter, u64 next_ts)
> > @@ -506,8 +520,7 @@ lat_print_timestamp(struct trace_iterator *iter, u64 next_ts)
> >  		return trace_seq_printf(
> >  				s, " %4lldus%c: ",
> >  				abs_ts,
> > -				rel_ts > preempt_mark_thresh_us ? '!' :
> > -				  rel_ts > 1 ? '+' : ' ');
> > +				find_trace_mark(rel_ts * NSEC_PER_USEC));
> >  	} else { /* !verbose && !in_ns */
> >  		return trace_seq_printf(s, " %4lld: ", abs_ts);
> >  	}
> > @@ -692,7 +705,7 @@ int register_ftrace_event(struct trace_event *event)
> >  				goto out;
> >  
> >  		} else {
> > -			
> > +
> >  			event->type = next_event_type++;
> >  			list = &ftrace_event_list;
> >  		}
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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Re: [PATCH v4 3/3] tracing: add additional marks to signal very large delay

[Namhyung Kim]

On Wed, 19 Nov 2014 13:35:15 -0500, Steven Rostedt wrote:
> On Tue, 18 Nov 2014 14:57:26 +0900
> byungchul.park@lge.com wrote:
>
>> From: Byungchul Park <byungchul.park@lge.com>
>> 
>> Currently, some tracers tracing latency print "!" or "+" just after time
>> to signal overhead, depending on the interval between events. Even it is
>> usually enough to do that, we sometimes need to be signaled for bigger
>> interval than 100 micro seconds.
>> 
>> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
>> ---
>>  Documentation/trace/ftrace.txt |    8 +++++---
>>  kernel/trace/trace_output.c    |   23 ++++++++++++++++++-----
>>  2 files changed, 23 insertions(+), 8 deletions(-)
>> 
>> diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
>> index f827e2f..64efb3e 100644
>> --- a/Documentation/trace/ftrace.txt
>> +++ b/Documentation/trace/ftrace.txt
>> @@ -680,9 +680,11 @@ The above is mostly meaningful for kernel developers.
>>  	 needs to be fixed to be only relative to the same CPU.
>>  	 The marks are determined by the difference between this
>>  	 current trace and the next trace.
>> -	  '!' - greater than preempt_mark_thresh (default 100)
>> -	  '+' - greater than 1 microsecond
>> -	  ' ' - less than or equal to 1 microsecond.
>> +	  '$' - greater than 1 second
>> +	  '#' - greater than 1000 microsecond
>> +	  '!' - greater than 100 microsecond
>> +	  '+' - greater than 10 microsecond

I've noticed that it's now changed from 1 msec to 10 msec.  Is it okay?

Thanks,
Namhyung


>> +	  ' ' - less than or equal to 10 microsecond.
>>  
>>    The rest is the same as the 'trace' file.

Re: [PATCH v4 3/3] tracing: add additional marks to signal very large delay

[Byungchul Park]

Hi, namhyung

On Thu, Nov 20, 2014 at 03:11:19PM +0900, Namhyung Kim wrote:
> On Wed, 19 Nov 2014 13:35:15 -0500, Steven Rostedt wrote:
> > On Tue, 18 Nov 2014 14:57:26 +0900
> > byungchul.park@lge.com wrote:
> >
> >> From: Byungchul Park <byungchul.park@lge.com>
> >> 
> >> Currently, some tracers tracing latency print "!" or "+" just after time
> >> to signal overhead, depending on the interval between events. Even it is
> >> usually enough to do that, we sometimes need to be signaled for bigger
> >> interval than 100 micro seconds.
> >> 
> >> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> >> ---
> >>  Documentation/trace/ftrace.txt |    8 +++++---
> >>  kernel/trace/trace_output.c    |   23 ++++++++++++++++++-----
> >>  2 files changed, 23 insertions(+), 8 deletions(-)
> >> 
> >> diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
> >> index f827e2f..64efb3e 100644
> >> --- a/Documentation/trace/ftrace.txt
> >> +++ b/Documentation/trace/ftrace.txt
> >> @@ -680,9 +680,11 @@ The above is mostly meaningful for kernel developers.
> >>  	 needs to be fixed to be only relative to the same CPU.
> >>  	 The marks are determined by the difference between this
> >>  	 current trace and the next trace.
> >> -	  '!' - greater than preempt_mark_thresh (default 100)
> >> -	  '+' - greater than 1 microsecond
> >> -	  ' ' - less than or equal to 1 microsecond.
> >> +	  '$' - greater than 1 second
> >> +	  '#' - greater than 1000 microsecond
> >> +	  '!' - greater than 100 microsecond
> >> +	  '+' - greater than 10 microsecond
> 
> I've noticed that it's now changed from 1 msec to 10 msec.  Is it okay?
>

Yes it is okay. Steve asked for changing the value. :)

Thanks,
Byungchul
 
> Thanks,
> Namhyung
> 
> 
> >> +	  ' ' - less than or equal to 10 microsecond.
> >>  
> >>    The rest is the same as the 'trace' file.
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Re: [PATCH v4 3/3] tracing: add additional marks to signal very large delay

[Steven Rostedt]

On Thu, 20 Nov 2014 15:11:19 +0900
Namhyung Kim <namhyung@kernel.org> wrote:


> >> +	  '#' - greater than 1000 microsecond
> >> +	  '!' - greater than 100 microsecond
> >> +	  '+' - greater than 10 microsecond
> 
> I've noticed that it's now changed from 1 msec to 10 msec.  Is it okay?

Yeah, I didn't like the inconsistency between the two tracers, and not
only that, I  found the 1 microsecond mark rather useless. 10 is a much
better value. I don't think people will complain about this API change.

-- Steve