[Patch RFC 0/2] tracing: allow disabling compilation of specific trace systems

[Patch RFC 0/2] tracing: allow disabling compilation of specific trace systems

[Tal Shorer]

Currently, enabling CONFIG_TRACING on a system comes as all-or-nothing: either
tracepoints for all subsystems are compiled (with CONFIG_TRACING) or none of
them do (without it).

This caused me an unacceptable performance penalty (obviously SOME penalty was
expected, but not one so severe) which made me revert the changes in
configuration.

The first patch in this series modifies the files that actually define the
tracepoint to look for a preprocessor macro NOTRACE and define nops (as if
CONFIG_TRACING was not set) instead of them.

The second patch provides an example of how I see this working, with the gpio
subsystem as the example for absolutely no reason.
If this idea is deemed worth the time by the community, I'll create patches for
the other subsystems.

Tal Shorer (2):
  tracing: allow disabling compilation of specific trace systems
  tracing: gpio: add Kconfig option for enabling/disabling trace events

 drivers/gpio/Kconfig         | 6 ++++++
 include/linux/tracepoint.h   | 6 +++---
 include/trace/define_trace.h | 2 +-
 include/trace/events/gpio.h  | 4 ++++
 4 files changed, 14 insertions(+), 4 deletions(-)

-- 
2.2.2

[Patch RFC 1/2] tracing: allow disabling compilation of specific trace systems

[Tal Shorer]

Allow a trace events header file to disable compilation of its
trace events by defining the preprocessor macro NOTRACE.

This could be done, for example, according to a Kconfig option.

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
---
 include/linux/tracepoint.h   | 6 +++---
 include/trace/define_trace.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a5f7f3e..c869f84 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -111,7 +111,7 @@ extern void syscall_unregfunc(void);
 #define TP_ARGS(args...)	args
 #define TP_CONDITION(args...)	args
 
-#ifdef CONFIG_TRACEPOINTS
+#if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
 
 /*
  * it_func[0] is never NULL because there is at least one element in the array
@@ -234,7 +234,7 @@ extern void syscall_unregfunc(void);
 #define EXPORT_TRACEPOINT_SYMBOL(name)					\
 	EXPORT_SYMBOL(__tracepoint_##name)
 
-#else /* !CONFIG_TRACEPOINTS */
+#else /* !(defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)) */
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 	static inline void trace_##name(proto)				\
 	{ }								\
@@ -266,7 +266,7 @@ extern void syscall_unregfunc(void);
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)
 
-#endif /* CONFIG_TRACEPOINTS */
+#endif /* defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE) */
 
 #ifdef CONFIG_TRACING
 /**
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index 02e1003..e847fd7 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -86,7 +86,7 @@
 #undef DECLARE_TRACE
 #define DECLARE_TRACE(name, proto, args)
 
-#ifdef CONFIG_EVENT_TRACING
+#if defined(CONFIG_EVENT_TRACING) && !defined(NOTRACE)
 #include <trace/ftrace.h>
 #endif
 
-- 
2.2.2

[Patch RFC 2/2] tracing: gpio: add Kconfig option for enabling/disabling trace events

[Tal Shorer]

Add a new options to gpio Kconfig, CONFIG_GPIO_TRACING, that is used
for enabling/disabling compilation of gpio function trace events.

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
---
 drivers/gpio/Kconfig        | 6 ++++++
 include/trace/events/gpio.h | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index caefe80..1480a22 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -88,6 +88,12 @@ config GPIO_SYSFS
 config GPIO_GENERIC
 	tristate
 
+config GPIO_TRACING
+	bool "gpio tracing"
+	depends on TRACING
+	help
+	  Enable tracing for gpio subsystem
+
 # put drivers in the right section, in alphabetical order
 
 # This symbol is selected by both I2C and SPI expanders
diff --git a/include/trace/events/gpio.h b/include/trace/events/gpio.h
index 927a8ad..09af636 100644
--- a/include/trace/events/gpio.h
+++ b/include/trace/events/gpio.h
@@ -1,6 +1,10 @@
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM gpio
 
+#ifndef CONFIG_GPIO_TRACING
+#define NOTRACE
+#endif
+
 #if !defined(_TRACE_GPIO_H) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_GPIO_H
 
-- 
2.2.2

Re: [Patch RFC 1/2] tracing: allow disabling compilation of specific trace systems

[Tal Shorer]

On Mon, Jul 13, 2015 at 9:34 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Sat, 20 Jun 2015 23:21:18 +0300
> Tal Shorer <tal.shorer@gmail.com> wrote:
>
>> Allow a trace events header file to disable compilation of its
>> trace events by defining the preprocessor macro NOTRACE.
>>
>> This could be done, for example, according to a Kconfig option.
>>
>> Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
>> ---
>>  include/linux/tracepoint.h   | 6 +++---
>>  include/trace/define_trace.h | 2 +-
>>  2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
>> index a5f7f3e..c869f84 100644
>> --- a/include/linux/tracepoint.h
>> +++ b/include/linux/tracepoint.h
>> @@ -111,7 +111,7 @@ extern void syscall_unregfunc(void);
>>  #define TP_ARGS(args...)     args
>>  #define TP_CONDITION(args...)        args
>>
>> -#ifdef CONFIG_TRACEPOINTS
>> +#if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
>
> Instead of the duplicate condition above, it would be better to make a
> new macro at the top. And we can add a nice comment to it as well.
Technically they're a little different, one with CONFIG_TRACEPOINTS
and the other with CONFIG_EVENT_TRACING.
Looking briefly at the Kconfig files, it appears you can't really have
CONFIG_TRACEPOINTS without also getting CONFIG_EVENT_TRACING along the
way.
If it's fine with you to effectively change the check for
CONFIG_EVENT_TRACING with a check for CONFIG_TRACEPOINTS (or vice
versa, let me know if you have a preference), it's fine with me and
will be added in v2.
>
> /*
>  * Individual subsystem my have a separate configuration to
>  * enable their tracepoints. By default, this file will create
>  * the tracepoints if CONFIG_TRACEPOINT is defined. If a subsystem
>  * wants to be able to disable its tracepoints from being created
>  * it can define NOTRACE before including the tracepoint headers.
>  */
Will be added in v2. I believe I'll have time to write and test it
during the week.
> #if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
> # define TRACEPOINTS_ENABLED
> #endif
>
> Then switch all the conditions below to:
>
> #ifdef TRACEPOINTS_ENABLED
>
> -- Steve
>
>
>>
>>  /*
>>   * it_func[0] is never NULL because there is at least one element in the array
>> @@ -234,7 +234,7 @@ extern void syscall_unregfunc(void);
>>  #define EXPORT_TRACEPOINT_SYMBOL(name)                                       \
>>       EXPORT_SYMBOL(__tracepoint_##name)
>>
>> -#else /* !CONFIG_TRACEPOINTS */
>> +#else /* !(defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)) */
>>  #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
>>       static inline void trace_##name(proto)                          \
>>       { }                                                             \
>> @@ -266,7 +266,7 @@ extern void syscall_unregfunc(void);
>>  #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
>>  #define EXPORT_TRACEPOINT_SYMBOL(name)
>>
>> -#endif /* CONFIG_TRACEPOINTS */
>> +#endif /* defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE) */
>>
>>  #ifdef CONFIG_TRACING
>>  /**
>> diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
>> index 02e1003..e847fd7 100644
>> --- a/include/trace/define_trace.h
>> +++ b/include/trace/define_trace.h
>> @@ -86,7 +86,7 @@
>>  #undef DECLARE_TRACE
>>  #define DECLARE_TRACE(name, proto, args)
>>
>> -#ifdef CONFIG_EVENT_TRACING
>> +#if defined(CONFIG_EVENT_TRACING) && !defined(NOTRACE)
>>  #include <trace/ftrace.h>
>>  #endif
>>
>

Re: [Patch RFC 1/2] tracing: allow disabling compilation of specific trace systems

[Steven Rostedt]

On Sat, 20 Jun 2015 23:21:18 +0300
Tal Shorer <tal.shorer@gmail.com> wrote:

> Allow a trace events header file to disable compilation of its
> trace events by defining the preprocessor macro NOTRACE.
> 
> This could be done, for example, according to a Kconfig option.
> 
> Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
> ---
>  include/linux/tracepoint.h   | 6 +++---
>  include/trace/define_trace.h | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index a5f7f3e..c869f84 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -111,7 +111,7 @@ extern void syscall_unregfunc(void);
>  #define TP_ARGS(args...)	args
>  #define TP_CONDITION(args...)	args
>  
> -#ifdef CONFIG_TRACEPOINTS
> +#if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)

Instead of the duplicate condition above, it would be better to make a
new macro at the top. And we can add a nice comment to it as well.

/*
 * Individual subsystem my have a separate configuration to
 * enable their tracepoints. By default, this file will create
 * the tracepoints if CONFIG_TRACEPOINT is defined. If a subsystem
 * wants to be able to disable its tracepoints from being created
 * it can define NOTRACE before including the tracepoint headers.
 */
#if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
# define TRACEPOINTS_ENABLED
#endif

Then switch all the conditions below to:

#ifdef TRACEPOINTS_ENABLED

-- Steve


>  
>  /*
>   * it_func[0] is never NULL because there is at least one element in the array
> @@ -234,7 +234,7 @@ extern void syscall_unregfunc(void);
>  #define EXPORT_TRACEPOINT_SYMBOL(name)					\
>  	EXPORT_SYMBOL(__tracepoint_##name)
>  
> -#else /* !CONFIG_TRACEPOINTS */
> +#else /* !(defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)) */
>  #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
>  	static inline void trace_##name(proto)				\
>  	{ }								\
> @@ -266,7 +266,7 @@ extern void syscall_unregfunc(void);
>  #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
>  #define EXPORT_TRACEPOINT_SYMBOL(name)
>  
> -#endif /* CONFIG_TRACEPOINTS */
> +#endif /* defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE) */
>  
>  #ifdef CONFIG_TRACING
>  /**
> diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
> index 02e1003..e847fd7 100644
> --- a/include/trace/define_trace.h
> +++ b/include/trace/define_trace.h
> @@ -86,7 +86,7 @@
>  #undef DECLARE_TRACE
>  #define DECLARE_TRACE(name, proto, args)
>  
> -#ifdef CONFIG_EVENT_TRACING
> +#if defined(CONFIG_EVENT_TRACING) && !defined(NOTRACE)
>  #include <trace/ftrace.h>
>  #endif
>  

[Patch RFC 1/2] tracing: allow disabling compilation of specific trace systems

[Tal Shorer]

Allow a trace events header file to disable compilation of its
trace events by defining the preprocessor macro NOTRACE.

This could be done, for example, according to a Kconfig option.

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
---
 include/linux/tracepoint.h   | 6 +++---
 include/trace/define_trace.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a5f7f3e..c869f84 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -111,7 +111,7 @@ extern void syscall_unregfunc(void);
 #define TP_ARGS(args...)	args
 #define TP_CONDITION(args...)	args
 
-#ifdef CONFIG_TRACEPOINTS
+#if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
 
 /*
  * it_func[0] is never NULL because there is at least one element in the array
@@ -234,7 +234,7 @@ extern void syscall_unregfunc(void);
 #define EXPORT_TRACEPOINT_SYMBOL(name)					\
 	EXPORT_SYMBOL(__tracepoint_##name)
 
-#else /* !CONFIG_TRACEPOINTS */
+#else /* !(defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)) */
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 	static inline void trace_##name(proto)				\
 	{ }								\
@@ -266,7 +266,7 @@ extern void syscall_unregfunc(void);
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)
 
-#endif /* CONFIG_TRACEPOINTS */
+#endif /* defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE) */
 
 #ifdef CONFIG_TRACING
 /**
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index 02e1003..e847fd7 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -86,7 +86,7 @@
 #undef DECLARE_TRACE
 #define DECLARE_TRACE(name, proto, args)
 
-#ifdef CONFIG_EVENT_TRACING
+#if defined(CONFIG_EVENT_TRACING) && !defined(NOTRACE)
 #include <trace/ftrace.h>
 #endif
 
-- 
2.2.2

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[Patch RFC 1/2] tracing: allow disabling compilation of specific trace systems

[Tal Shorer]

Allow a trace events header file to disable compilation of its
trace events by defining the preprocessor macro NOTRACE.

This could be done, for example, according to a Kconfig option.

Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
---
 include/linux/tracepoint.h   | 6 +++---
 include/trace/define_trace.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a5f7f3e..c869f84 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -111,7 +111,7 @@ extern void syscall_unregfunc(void);
 #define TP_ARGS(args...)	args
 #define TP_CONDITION(args...)	args
 
-#ifdef CONFIG_TRACEPOINTS
+#if defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)
 
 /*
  * it_func[0] is never NULL because there is at least one element in the array
@@ -234,7 +234,7 @@ extern void syscall_unregfunc(void);
 #define EXPORT_TRACEPOINT_SYMBOL(name)					\
 	EXPORT_SYMBOL(__tracepoint_##name)
 
-#else /* !CONFIG_TRACEPOINTS */
+#else /* !(defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE)) */
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
 	static inline void trace_##name(proto)				\
 	{ }								\
@@ -266,7 +266,7 @@ extern void syscall_unregfunc(void);
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)
 
-#endif /* CONFIG_TRACEPOINTS */
+#endif /* defined(CONFIG_TRACEPOINTS) && !defined(NOTRACE) */
 
 #ifdef CONFIG_TRACING
 /**
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index 02e1003..e847fd7 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -86,7 +86,7 @@
 #undef DECLARE_TRACE
 #define DECLARE_TRACE(name, proto, args)
 
-#ifdef CONFIG_EVENT_TRACING
+#if defined(CONFIG_EVENT_TRACING) && !defined(NOTRACE)
 #include <trace/ftrace.h>
 #endif
 
-- 
2.2.2