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Message-ID: <c62985530910120209t3d263d5eh5aeba14fcecc9072@mail.gmail.com>
Date: Mon, 12 Oct 2009 11:09:33 +0200
From: Frédéric Weisbecker <fweisbec@...il.com>
To: Stefan Assmann <sassmann@...hat.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
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.
> 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..a5cae5c 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 +2322,31 @@ 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;
> +
> + 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 +2363,10 @@ 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
> --
> 1.6.2.5
>
>
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