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Date: Mon, 12 Oct 2009 12:05:34 +0200
From: Stefan Assmann <sassmann@...hat.com>
To: Frédéric Weisbecker <fweisbec@...il.com>
CC: rostedt@...dmis.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace: add kernel command line graph function filtering
On 12.10.2009 11:09, Frédéric Weisbecker wrote:
> 2009/10/12 Stefan Assmann <sassmann@...hat.com>:
>> From 894e934e782ddaa33eb6d156d8326cdf479b5f62 Mon Sep 17 00:00:00 2001
>> From: Stefan Assmann <sassmann@...hat.com>
>> Date: Mon, 12 Oct 2009 09:11:47 +0200
>> Subject: [PATCH] ftrace: add kernel command line graph function filtering
>>
>> Add a command line parameter to allow limiting the function graphs that
>> are traced on boot up, when ftrace=function_graph is specified.
>>
>> This patch adds the following command line option:
>> ftrace_graph_filter=function-list
>
>
> If we use this parameter, we undoubtedly want to launch the function
> graph tracer.
> I'd then suggest to arm ftrace=function_graph automatically if we have
> ftrace_graph_filter
> set.
>
>
>>
>> Where function-list is a comma separated list of functions to filter.
>>
>> Signed-off-by: Stefan Assmann <sassmann@...hat.com>
>> ---
>> Documentation/kernel-parameters.txt | 9 ++++++++-
>> kernel/trace/ftrace.c | 34 ++++++++++++++++++++++++++++++++++
>> 2 files changed, 42 insertions(+), 1 deletions(-)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index 9107b38..144eb83 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -771,7 +771,14 @@ and is between 256 and 4096 characters. It is defined in the file
>> tracer at boot up. function-list is a comma separated
>> list of functions. This list can be changed at run
>> time by the set_ftrace_filter file in the debugfs
>> - tracing directory.
>> + tracing directory.
>> +
>> + ftrace_graph_filter=[function-list]
>> + [FTRACE] Limit the functions traced by the function
>> + graph tracer at boot up. function-list is a comma
>> + separated list of functions. This list can be changed
>> + at run time by the set_graph_function file in the
>> + debugfs tracing directory.
>
>
>
> May be you should use a more detailed definition of this parameter.
> Limiting a function traced by the function graph tracer is ambiguous.
>
> It means we can have either:
>
> function_to_trace();
>
> or:
>
> function_to_trace() {
> foo() {
> bar();
> }
> }
>
> We want the second thing.
> May be instead you can write:
>
> "Limit the top level callers functions traced by the function
> graph tracer at boot up."
>
> Otherwise, looks good to me:
>
> Acked-by: Frederic Weisbecker <fweisbec@...il.com>
>
> Thanks.
Thanks for reviewing Frédéric!
I hope the following is what you had in mind.
Stefan
>From edeb75ce9c9a35d5905d45954f66a0e05d5fe8ab Mon Sep 17 00:00:00 2001
From: Stefan Assmann <sassmann@...hat.com>
Date: Mon, 12 Oct 2009 09:11:47 +0200
Subject: [PATCH] ftrace: add kernel command line graph function filtering
Add a command line parameter to allow limiting the top level callers functions
traced by the function graph tracer at boot up.
This patch adds the following command line option:
ftrace_graph_filter=function-list
Where function-list is a comma separated list of functions to filter.
Signed-off-by: Stefan Assmann <sassmann@...hat.com>
---
Documentation/kernel-parameters.txt | 9 ++++++++-
kernel/trace/ftrace.c | 35 +++++++++++++++++++++++++++++++++++
kernel/trace/trace.c | 2 +-
kernel/trace/trace.h | 1 +
4 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9107b38..539a053 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -771,7 +771,14 @@ and is between 256 and 4096 characters. It is defined in the file
tracer at boot up. function-list is a comma separated
list of functions. This list can be changed at run
time by the set_ftrace_filter file in the debugfs
- tracing directory.
+ tracing directory.
+
+ ftrace_graph_filter=[function-list]
+ [FTRACE] Limit the top level callers functions traced
+ by the function graph tracer at boot up.
+ function-list is a comma separated list of functions
+ that can be changed at run time by the
+ set_graph_function file in the debugfs tracing directory.
ftrace_notrace=[function-list]
[FTRACE] Do not trace the functions specified in
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 3724756..ee9c509 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -78,6 +78,10 @@ ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static int ftrace_set_func(unsigned long *array, int *idx, char *buffer);
+#endif
+
static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
{
struct ftrace_ops *op = ftrace_list;
@@ -2302,6 +2306,7 @@ void ftrace_set_notrace(unsigned char *buf, int len, int reset)
#define FTRACE_FILTER_SIZE COMMAND_LINE_SIZE
static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;
+static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
static int __init set_ftrace_notrace(char *str)
{
@@ -2317,6 +2322,32 @@ static int __init set_ftrace_filter(char *str)
}
__setup("ftrace_filter=", set_ftrace_filter);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static int __init set_graph_function(char *str)
+{
+ strncpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
+ return 1;
+}
+__setup("ftrace_graph_filter=", set_graph_function);
+
+static void __init set_ftrace_early_graph(char *buf)
+{
+ int ret;
+ char *func;
+
+ set_ftrace("function_graph");
+ while (buf) {
+ func = strsep(&buf, ",");
+ /* we allow only one expression at a time */
+ ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
+ func);
+ if (ret)
+ printk(KERN_DEBUG "ftrace: function %s not "
+ "traceable\n", func);
+ }
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
static void __init set_ftrace_early_filter(char *buf, int enable)
{
char *func;
@@ -2333,6 +2364,10 @@ static void __init set_ftrace_early_filters(void)
set_ftrace_early_filter(ftrace_filter_buf, 1);
if (ftrace_notrace_buf[0])
set_ftrace_early_filter(ftrace_notrace_buf, 0);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ if (ftrace_graph_buf[0])
+ set_ftrace_early_graph(ftrace_graph_buf);
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
}
static int
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4506826..811c918 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -129,7 +129,7 @@ static int tracing_set_tracer(const char *buf);
static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
static char *default_bootup_tracer;
-static int __init set_ftrace(char *str)
+int __init set_ftrace(char *str)
{
strncpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
default_bootup_tracer = bootup_tracer_buf;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 405cb85..4625acc 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -461,6 +461,7 @@ extern int trace_clock_id;
extern enum print_line_t print_graph_function(struct trace_iterator *iter);
extern enum print_line_t
trace_print_graph_duration(unsigned long long duration, struct trace_seq *s);
+extern int set_ftrace(char *str);
#ifdef CONFIG_DYNAMIC_FTRACE
/* TODO: make this variable */
--
1.6.2.5
--
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