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Date: Fri, 17 Feb 2023 21:04:41 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Ross Zwisler <zwisler@...omium.org>, <linux-kernel@...r.kernel.org>
CC: Ross Zwisler <zwisler@...gle.com>,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
<linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/6] tracing: always use canonical ftrace path
On 2/16/2023 4:03 AM, Ross Zwisler wrote:
> The canonical location for the tracefs filesystem is at /sys/kernel/tracing.
>
> But, from Documentation/trace/ftrace.rst:
>
> Before 4.1, all ftrace tracing control files were within the debugfs
> file system, which is typically located at /sys/kernel/debug/tracing.
> For backward compatibility, when mounting the debugfs file system,
> the tracefs file system will be automatically mounted at:
>
> /sys/kernel/debug/tracing
>
> Many comments and Kconfig help messages in the tracing code still refer
> to this older debugfs path, so let's update them to avoid confusion.
>
> Signed-off-by: Ross Zwisler <zwisler@...gle.com>
> ---
> include/linux/kernel.h | 2 +-
> include/linux/tracepoint.h | 4 ++--
> kernel/trace/Kconfig | 20 ++++++++++----------
> kernel/trace/kprobe_event_gen_test.c | 2 +-
> kernel/trace/ring_buffer.c | 2 +-
> kernel/trace/synth_event_gen_test.c | 2 +-
> kernel/trace/trace.c | 2 +-
> samples/user_events/example.c | 4 ++--
> scripts/tracing/draw_functrace.py | 6 +++---
> tools/lib/api/fs/tracing_path.c | 4 ++--
> tools/tracing/latency/latency-collector.c | 2 +-
> 11 files changed, 25 insertions(+), 25 deletions(-)
>
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index fe6efb24d151..40bce7495af8 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -297,7 +297,7 @@ bool mac_pton(const char *s, u8 *mac);
> *
> * Use tracing_on/tracing_off when you want to quickly turn on or off
> * tracing. It simply enables or disables the recording of the trace events.
> - * This also corresponds to the user space /sys/kernel/debug/tracing/tracing_on
> + * This also corresponds to the user space /sys/kernel/tracing/tracing_on
> * file, which gives a means for the kernel and userspace to interact.
> * Place a tracing_off() in the kernel where you want tracing to end.
> * From user space, examine the trace, and then echo 1 > tracing_on
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index 4b33b95eb8be..fa1004fcf810 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -471,7 +471,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
> * * This is how the trace record is structured and will
> * * be saved into the ring buffer. These are the fields
> * * that will be exposed to user-space in
> - * * /sys/kernel/debug/tracing/events/<*>/format.
> + * * /sys/kernel/tracing/events/<*>/format.
> * *
> * * The declared 'local variable' is called '__entry'
> * *
> @@ -531,7 +531,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
> * tracepoint callback (this is used by programmatic plugins and
> * can also by used by generic instrumentation like SystemTap), and
> * it is also used to expose a structured trace record in
> - * /sys/kernel/debug/tracing/events/.
> + * /sys/kernel/tracing/events/.
> *
> * A set of (un)registration functions can be passed to the variant
> * TRACE_EVENT_FN to perform any (un)registration work.
> diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> index d7043043f59c..5f5e64f9e715 100644
> --- a/kernel/trace/Kconfig
> +++ b/kernel/trace/Kconfig
> @@ -239,7 +239,7 @@ config DYNAMIC_FTRACE
> enabled, and the functions not enabled will not affect
> performance of the system.
>
> - See the files in /sys/kernel/debug/tracing:
> + See the files in /sys/kernel/tracing:
> available_filter_functions
> set_ftrace_filter
> set_ftrace_notrace
> @@ -299,7 +299,7 @@ config STACK_TRACER
> select KALLSYMS
> help
> This special tracer records the maximum stack footprint of the
> - kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
> + kernel and displays it in /sys/kernel/tracing/stack_trace.
>
> This tracer works by hooking into every function call that the
> kernel executes, and keeping a maximum stack depth value and
> @@ -339,7 +339,7 @@ config IRQSOFF_TRACER
> disabled by default and can be runtime (re-)started
> via:
>
> - echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
> + echo 0 > /sys/kernel/tracing/tracing_max_latency
>
> (Note that kernel size and overhead increase with this option
> enabled. This option and the preempt-off timing option can be
> @@ -363,7 +363,7 @@ config PREEMPT_TRACER
> disabled by default and can be runtime (re-)started
> via:
>
> - echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
> + echo 0 > /sys/kernel/tracing/tracing_max_latency
>
> (Note that kernel size and overhead increase with this option
> enabled. This option and the irqs-off timing option can be
> @@ -515,7 +515,7 @@ config TRACER_SNAPSHOT
> Allow tracing users to take snapshot of the current buffer using the
> ftrace interface, e.g.:
>
> - echo 1 > /sys/kernel/debug/tracing/snapshot
> + echo 1 > /sys/kernel/tracing/snapshot
> cat snapshot
>
> config TRACER_SNAPSHOT_PER_CPU_SWAP
> @@ -527,7 +527,7 @@ config TRACER_SNAPSHOT_PER_CPU_SWAP
> full swap (all buffers). If this is set, then the following is
> allowed:
>
> - echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
> + echo 1 > /sys/kernel/tracing/per_cpu/cpu2/snapshot
>
> After which, only the tracing buffer for CPU 2 was swapped with
> the main tracing buffer, and the other CPU buffers remain the same.
> @@ -574,7 +574,7 @@ config PROFILE_ANNOTATED_BRANCHES
> This tracer profiles all likely and unlikely macros
> in the kernel. It will display the results in:
>
> - /sys/kernel/debug/tracing/trace_stat/branch_annotated
> + /sys/kernel/tracing/trace_stat/branch_annotated
>
> Note: this will add a significant overhead; only turn this
> on if you need to profile the system's use of these macros.
> @@ -587,7 +587,7 @@ config PROFILE_ALL_BRANCHES
> taken in the kernel is recorded whether it hit or miss.
> The results will be displayed in:
>
> - /sys/kernel/debug/tracing/trace_stat/branch_all
> + /sys/kernel/tracing/trace_stat/branch_all
>
> This option also enables the likely/unlikely profiler.
>
> @@ -638,8 +638,8 @@ config BLK_DEV_IO_TRACE
> Tracing also is possible using the ftrace interface, e.g.:
>
> echo 1 > /sys/block/sda/sda1/trace/enable
> - echo blk > /sys/kernel/debug/tracing/current_tracer
> - cat /sys/kernel/debug/tracing/trace_pipe
> + echo blk > /sys/kernel/tracing/current_tracer
> + cat /sys/kernel/tracing/trace_pipe
>
> If unsure, say N.
>
> diff --git a/kernel/trace/kprobe_event_gen_test.c b/kernel/trace/kprobe_event_gen_test.c
> index c736487fc0e4..4850fdfe27f1 100644
> --- a/kernel/trace/kprobe_event_gen_test.c
> +++ b/kernel/trace/kprobe_event_gen_test.c
> @@ -21,7 +21,7 @@
> * Then:
> *
> * # insmod kernel/trace/kprobe_event_gen_test.ko
> - * # cat /sys/kernel/debug/tracing/trace
> + * # cat /sys/kernel/tracing/trace
> *
> * You should see many instances of the "gen_kprobe_test" and
> * "gen_kretprobe_test" events in the trace buffer.
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index c366a0a9ddba..4cdb2feccff3 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -2886,7 +2886,7 @@ rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
> sched_clock_stable() ? "" :
> "If you just came from a suspend/resume,\n"
> "please switch to the trace global clock:\n"
> - " echo global > /sys/kernel/debug/tracing/trace_clock\n"
> + " echo global > /sys/kernel/tracing/trace_clock\n"
> "or add trace_clock=global to the kernel command line\n");
> }
>
> diff --git a/kernel/trace/synth_event_gen_test.c b/kernel/trace/synth_event_gen_test.c
> index 8d77526892f4..8dfe85499d4a 100644
> --- a/kernel/trace/synth_event_gen_test.c
> +++ b/kernel/trace/synth_event_gen_test.c
> @@ -22,7 +22,7 @@
> * Then:
> *
> * # insmod kernel/trace/synth_event_gen_test.ko
> - * # cat /sys/kernel/debug/tracing/trace
> + * # cat /sys/kernel/tracing/trace
> *
> * You should see several events in the trace buffer -
> * "create_synth_test", "empty_synth_test", and several instances of
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index c9e40f692650..1101220052b3 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1142,7 +1142,7 @@ void tracing_snapshot_instance(struct trace_array *tr)
> *
> * Note, make sure to allocate the snapshot with either
> * a tracing_snapshot_alloc(), or by doing it manually
> - * with: echo 1 > /sys/kernel/debug/tracing/snapshot
> + * with: echo 1 > /sys/kernel/tracing/snapshot
> *
> * If the snapshot buffer is not allocated, it will stop tracing.
> * Basically making a permanent snapshot.
> diff --git a/samples/user_events/example.c b/samples/user_events/example.c
> index d06dc24156ec..18e34c9d708e 100644
> --- a/samples/user_events/example.c
> +++ b/samples/user_events/example.c
> @@ -23,8 +23,8 @@
> #endif
>
> /* Assumes debugfs is mounted */
> -const char *data_file = "/sys/kernel/debug/tracing/user_events_data";
> -const char *status_file = "/sys/kernel/debug/tracing/user_events_status";
> +const char *data_file = "/sys/kernel/tracing/user_events_data";
> +const char *status_file = "/sys/kernel/tracing/user_events_status";
>
> static int event_status(long **status)
> {
> diff --git a/scripts/tracing/draw_functrace.py b/scripts/tracing/draw_functrace.py
> index 438516bdfb3c..42fa87300941 100755
> --- a/scripts/tracing/draw_functrace.py
> +++ b/scripts/tracing/draw_functrace.py
> @@ -12,9 +12,9 @@ calls. Only the functions's names and the call time are provided.
>
> Usage:
> Be sure that you have CONFIG_FUNCTION_TRACER
> - # mount -t debugfs nodev /sys/kernel/debug
> - # echo function > /sys/kernel/debug/tracing/current_tracer
> - $ cat /sys/kernel/debug/tracing/trace_pipe > ~/raw_trace_func
> + # mount -t tracefs nodev /sys/kernel/tracing
> + # echo function > /sys/kernel/tracing/current_tracer
> + $ cat /sys/kernel/tracing/trace_pipe > ~/raw_trace_func
> Wait some times but not too much, the script is a bit slow.
> Break the pipe (Ctrl + Z)
> $ scripts/tracing/draw_functrace.py < ~/raw_trace_func > draw_functrace
> diff --git a/tools/lib/api/fs/tracing_path.c b/tools/lib/api/fs/tracing_path.c
> index b8e457c841ab..7ba3e81274e8 100644
> --- a/tools/lib/api/fs/tracing_path.c
> +++ b/tools/lib/api/fs/tracing_path.c
> @@ -14,8 +14,8 @@
> #include "tracing_path.h"
>
> static char tracing_mnt[PATH_MAX] = "/sys/kernel/debug";
> -static char tracing_path[PATH_MAX] = "/sys/kernel/debug/tracing";
> -static char tracing_events_path[PATH_MAX] = "/sys/kernel/debug/tracing/events";
> +static char tracing_path[PATH_MAX] = "/sys/kernel/tracing";
> +static char tracing_events_path[PATH_MAX] = "/sys/kernel/tracing/events";
>
> static void __tracing_path_set(const char *tracing, const char *mountpoint)
> {
> diff --git a/tools/tracing/latency/latency-collector.c b/tools/tracing/latency/latency-collector.c
> index 59a7f2346eab..0fd9c747d396 100644
> --- a/tools/tracing/latency/latency-collector.c
> +++ b/tools/tracing/latency/latency-collector.c
> @@ -1584,7 +1584,7 @@ static void *do_printloop(void *arg)
> /*
> * Toss a coin to decide if we want to sleep before printing
> * out the backtrace. The reason for this is that opening
> - * /sys/kernel/debug/tracing/trace will cause a blackout of
> + * /sys/kernel/tracing/trace will cause a blackout of
> * hundreds of ms, where no latencies will be noted by the
> * latency tracer. Thus by randomly sleeping we try to avoid
> * missing traces systematically due to this. With this option
LGTM.
Reviewed-by: Mukesh Ojha <quic_mojha@...cinc.com>
-Mukesh
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