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20 authors
  1. Aug 26, 2024
    • Steven Rostedt's avatar
      tracing/Documentation: Start a document on how to debug with tracing · 2fcd5aff
      Steven Rostedt authored 
      Add a new document Documentation/trace/debugging.rst that will hold
various ways to debug tracing.

This initial version mentions trace_printk and how to create persistent
buffers that can last across bootups.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineeth Pillai <vineeth@bitbyteword.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ross Zwisler <zwisler@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Aring <aahringo@redhat.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Jonathan Corbet" <corbet@lwn.net>
Link: https://lore.kernel.org/20240823014019.702433486@goodmis.org


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
      2fcd5aff
    • Steven Rostedt's avatar
      tracing: Add option to set an instance to be the trace_printk destination · ef2bd81d
      Steven Rostedt authored 
      Add a option "trace_printk_dest" that will make the tracing instance the
location that trace_printk() will go to. This is useful if the
trace_printk or one of the top level tracers is too noisy and there's a
need to separate the two. Then an instance can be created, the
trace_printk can be set to go there instead, where it will not be lost in
the noise of the top level tracer.

Note, only one instance can be the destination of trace_printk at a time.
If an instance sets this flag, the instance that had it set will have it
cleared. There is always one instance that has this set. By default, that
is the top instance. This flag cannot be cleared from the top instance.
Doing so will result in an -EINVAL. The only way this flag can be cleared
from the top instance is by another instance setting it.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineeth Pillai <vineeth@bitbyteword.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ross Zwisler <zwisler@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Aring <aahringo@redhat.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Jonathan Corbet" <corbet@lwn.net>
Link: https://lore.kernel.org/20240823014019.545459018@goodmis.org


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
      ef2bd81d
  3. Jul 01, 2024
  5. Jun 11, 2024
    • Steven Rostedt (Google)'s avatar
      function_graph: Everyone uses HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, remove it · 5f7fb89a
      Steven Rostedt (Google) authored 
      All architectures that implement function graph also implements
HAVE_FUNCTION_GRAPH_RET_ADDR_PTR. Remove it, as it is no longer a
differentiator.

Link: https://lore.kernel.org/linux-trace-kernel/20240611031737.982047614@goodmis.org



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
      5f7fb89a
  7. May 13, 2024
  9. May 07, 2024
  11. May 02, 2024
  13. May 01, 2024
  15. Apr 02, 2024
  17. Mar 18, 2024
  19. Mar 06, 2024
  21. Jan 11, 2024
  23. Jan 03, 2024
  25. Dec 21, 2023
  27. Nov 17, 2023
  29. Nov 16, 2023
  31. Nov 10, 2023
  33. Oct 17, 2023
  35. Oct 04, 2023
  37. Sep 11, 2023
  39. Aug 23, 2023
  41. Aug 22, 2023
  43. Aug 18, 2023
  45. Jun 23, 2023
  47. Jun 22, 2023
    • Daniel Bristot de Oliveira's avatar
      tracing/timerlat: Add user-space interface · e88ed227
      Daniel Bristot de Oliveira authored 
      Going a step further, we propose a way to use any user-space
workload as the task waiting for the timerlat timer. This is done
via a per-CPU file named osnoise/cpu$id/timerlat_fd file.

The tracef_fd allows a task to open at a time. When a task reads
the file, the timerlat timer is armed for future osnoise/timerlat_period_us
time. When the timer fires, it prints the IRQ latency and
wakes up the user-space thread waiting in the timerlat_fd.

The thread then starts to run, executes the timerlat measurement, prints
the thread scheduling latency and returns to user-space.

When the thread rereads the timerlat_fd, the tracer will print the
user-ret(urn) latency, which is an additional metric.

This additional metric is also traced by the tracer and can be used, for
example of measuring the context switch overhead from kernel-to-user and
user-to-kernel, or the response time for an arbitrary execution in
user-space.

The tracer supports one thread per CPU, the thread must be pinned to
the CPU, and it cannot migrate while holding the timerlat_fd. The reason
is that the tracer is per CPU (nothing prohibits the tracer from
allowing migrations in the future). The tracer monitors the migration
of the thread and disables the tracer if detected.

The timerlat_fd is only available for opening/reading when timerlat
tracer is enabled, and NO_OSNOISE_WORKLOAD is set.

The simplest way to activate this feature from user-space is:

 -------------------------------- %< -----------------------------------
 int main(void)
 {
	char buffer[1024];
	int timerlat_fd;
	int retval;
	long cpu = 0;	/* place in CPU 0 */
	cpu_set_t set;

	CPU_ZERO(&set);
	CPU_SET(cpu, &set);

	if (sched_setaffinity(gettid(), sizeof(set), &set) == -1)
		return 1;

	snprintf(buffer, sizeof(buffer),
		"/sys/kernel/tracing/osnoise/per_cpu/cpu%ld/timerlat_fd",
		cpu);

	timerlat_fd = open(buffer, O_RDONLY);
	if (timerlat_fd < 0) {
		printf("error opening %s: %s\n", buffer, strerror(errno));
		exit(1);
	}

	for (;;) {
		retval = read(timerlat_fd, buffer, 1024);
		if (retval < 0)
			break;
	}

	close(timerlat_fd);
	exit(0);
}
 -------------------------------- >% -----------------------------------

When disabling timerlat, if there is a workload holding the timerlat_fd,
the SIGKILL will be sent to the thread.

Link: https://lkml.kernel.org/r/69fe66a863d2792ff4c3a149bf9e32e26468bb3a.1686063934.git.bristot@kernel.org



Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: William White <chwhite@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
      e88ed227
    • Jiri Olsa's avatar
      ftrace: Show all functions with addresses in available_filter_functions_addrs · 83f74441
      Jiri Olsa authored 
      Adding new available_filter_functions_addrs file that shows all available
functions (same as available_filter_functions) together with addresses,
like:

  # cat available_filter_functions_addrs | head
  ffffffff81000770 __traceiter_initcall_level
  ffffffff810007c0 __traceiter_initcall_start
  ffffffff81000810 __traceiter_initcall_finish
  ffffffff81000860 trace_initcall_finish_cb
  ...

Note displayed address is the patch-site address and can differ from
/proc/kallsyms address.

It's useful to have address avilable for traceable symbols, so we don't
need to allways cross check kallsyms with available_filter_functions
(or the other way around) and have all the data in single file.

For backwards compatibility reasons we can't change the existing
available_filter_functions file output, but we need to add new file.

The problem is that we need to do 2 passes:

 - through available_filter_functions and find out if the function is traceable
 - through /proc/kallsyms to get the address for traceable function

Having available_filter_functions symbols together with addresses allow
us to skip the kallsyms step and we are ok with the address in
available_filter_functions_addr not being the function entry, because
kprobe_multi uses fprobe and that handles both entry and patch-site
address properly.

We have 2 interfaces how to create kprobe_multi link:

  a) passing symbols to kernel

     1) user gathers symbols and need to ensure that they are
        trace-able -> pass through available_filter_functions file

     2) kernel takes those symbols and translates them to addresses
        through kallsyms api

     3) addresses are passed to fprobe/ftrace through:

         register_fprobe_ips
         -> ftrace_set_filter_ips

  b) passing addresses to kernel

     1) user gathers symbols and needs to ensure that they are
        trace-able -> pass through available_filter_functions file

     2) user takes those symbols and translates them to addresses
       through /proc/kallsyms

     3) addresses are passed to the kernel and kernel calls:

         register_fprobe_ips
         -> ftrace_set_filter_ips

The new available_filter_functions_addrs file helps us with option b),
because we can make 'b 1' and 'b 2' in one step - while filtering traceable
functions, we get the address directly.

Link: https://lore.kernel.org/linux-trace-kernel/20230611130029.1202298-1-jolsa@kernel.org



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Tested-by: Jackie Liu <liuyun01@kylinos.cn> # x86
Suggested-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Suggested-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
      83f74441
  49. Jun 21, 2023
  51. Jun 20, 2023
  53. Jun 15, 2023
  55. Jun 14, 2023
  57. Jun 06, 2023