Commit Graph

543 Commits

Author SHA1 Message Date
Ingo Molnar 6f5e3577d4 Merge branch 'tip/perf/core-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into perf/core 2012-05-21 09:44:36 +02:00
Ingo Molnar bb27f55eb9 Merge branch 'perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/core
Fixes for perf/core:

 - Rename some perf_target methods to avoid double negation, from Namhyung Kim.
 - Revert change to use per task events with inheritance, from Namhyung Kim.
 - Events should start disabled till children starts running, from David Ahern.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-21 09:17:50 +02:00
Richard Weinberger 895b67fd58 tracing: Remove kernel_lock annotations
The BKL is gone, these annotations are useless.

Link: http://lkml.kernel.org/r/1320654202-4433-1-git-send-email-richard@nod.at

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-19 08:28:51 -04:00
Vaibhav Nagarnaik a591c73f12 tracing: Fix initial buffer_size_kb state
Make sure that the state of buffer_size_kb is initialized correctly and
returns actual size of the ring buffer.

Link: http://lkml.kernel.org/r/1336066834-1673-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Laurent Chavey <chavey@google.com>
Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-19 08:28:50 -04:00
Arnaldo Carvalho de Melo 16ee6576e2 Merge remote-tracking branch 'tip/perf/urgent' into perf/core
Merge reason: We are going to queue up a dependent patch:

"perf tools: Move parse event automated tests to separated object"

That depends on:

commit e7c72d8
perf tools: Add 'G' and 'H' modifiers to event parsing

Conflicts:
	tools/perf/builtin-stat.c

Conflicted with the recent 'perf_target' patches when checking the
result of perf_evsel open routines to see if a retry is needed to cope
with older kernels where the exclude guest/host perf_event_attr bits
were not used.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2012-05-18 13:13:33 -03:00
Vaibhav Nagarnaik 71babb2705 tracing: change CPU ring buffer state from tracing_cpumask
According to Documentation/trace/ftrace.txt:

tracing_cpumask:

        This is a mask that lets the user only trace
        on specified CPUS. The format is a hex string
        representing the CPUS.

The tracing_cpumask currently doesn't affect the tracing state of
per-CPU ring buffers.

This patch enables/disables CPU recording as its corresponding bit in
tracing_cpumask is set/unset.

Link: http://lkml.kernel.org/r/1336096792-25373-3-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Laurent Chavey <chavey@google.com>
Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-16 19:50:38 -04:00
Namhyung Kim 0a3d7ce7e6 tracing: Check return value of tracing_dentry_percpu()
If tracing_dentry_percpu() failed, tracing_init_debugfs_percpu()
will try to create each cpu directories on debugfs' root directory
as d_percpu is NULL.

Link: http://lkml.kernel.org/r/1335143517-2285-1-git-send-email-namhyung.kim@lge.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-16 19:50:37 -04:00
Vaibhav Nagarnaik 83f40318da ring-buffer: Make removal of ring buffer pages atomic
This patch adds the capability to remove pages from a ring buffer
without destroying any existing data in it.

This is done by removing the pages after the tail page. This makes sure
that first all the empty pages in the ring buffer are removed. If the
head page is one in the list of pages to be removed, then the page after
the removed ones is made the head page. This removes the oldest data
from the ring buffer and keeps the latest data around to be read.

To do this in a non-racey manner, tracing is stopped for a very short
time while the pages to be removed are identified and unlinked from the
ring buffer. The pages are freed after the tracing is restarted to
minimize the time needed to stop tracing.

The context in which the pages from the per-cpu ring buffer are removed
runs on the respective CPU. This minimizes the events not traced to only
NMI trace contexts.

Link: http://lkml.kernel.org/r/1336096792-25373-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Laurent Chavey <chavey@google.com>
Cc: Justin Teravest <teravest@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-16 16:18:57 -04:00
Steven Rostedt 6edb2a8a38 tracing: Clean up tracing_mark_write()
On gcc 4.5 the function tracing_mark_write() would give a warning
of page2 being uninitialized. This is due to a bug in gcc because
the logic prevents page2 from being used uninitialized, and
gcc 4.6+ does not complain (correctly).

Instead of adding a "unitialized" around page2, which could show
a bug later on, I combined page1 and page2 into an array map_pages[].
This binds the two and the two are modified according to nr_pages
(what gcc 4.5 seems to ignore). This no longer gives a warning with
gcc 4.5 nor with gcc 4.6.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-16 16:18:57 -04:00
Steven Rostedt 68179686ac tracing: Remove ftrace_disable/enable_cpu()
The ftrace_disable_cpu() and ftrace_enable_cpu() functions were
needed back before the ring buffer was lockless. Now that the
ring buffer is lockless (and has been for some time), these functions
serve no purpose, and unnecessarily slow down operations of the tracer.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-08 21:06:26 -04:00
Jiri Olsa 50e18b94c6 tracing: Use seq_*_private interface for some seq files
It's appropriate to use __seq_open_private interface to open
some of trace seq files, because it covers all steps we are
duplicating in tracing code - zallocating the iterator and
setting it as seq_file's private.

Using this for following files:
  trace
  available_filter_functions
  enabled_functions

Link: http://lkml.kernel.org/r/1335342219-2782-5-git-send-email-jolsa@redhat.com

Signed-off-by: Jiri Olsa <jolsa@redhat.com>

[
 Fixed warnings for:
   kernel/trace/trace.c: In function '__tracing_open':
   kernel/trace/trace.c:2418:11: warning: unused variable 'ret' [-Wunused-variable]
   kernel/trace/trace.c:2417:19: warning: unused variable 'm' [-Wunused-variable]
]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-05-08 21:04:12 -04:00
Vaibhav Nagarnaik 438ced1720 ring-buffer: Add per_cpu ring buffer control files
Add a debugfs entry under per_cpu/ folder for each cpu called
buffer_size_kb to control the ring buffer size for each CPU
independently.

If the global file buffer_size_kb is used to set size, the individual
ring buffers will be adjusted to the given size. The buffer_size_kb will
report the common size to maintain backward compatibility.

If the buffer_size_kb file under the per_cpu/ directory is used to
change buffer size for a specific CPU, only the size of the respective
ring buffer is updated. When tracing/buffer_size_kb is read, it reports
'X' to indicate that sizes of per_cpu ring buffers are not equivalent.

Link: http://lkml.kernel.org/r/1328212844-11889-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Justin Teravest <teravest@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-04-23 21:17:51 -04:00
Dan Carpenter 5a26c8f0cf tracing: Remove an unneeded check in trace_seq_buffer()
memcpy() returns a pointer to "bug".  Hopefully, it's not NULL here or
we would already have Oopsed.

Link: http://lkml.kernel.org/r/20120420063145.GA22649@elgon.mountain

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-04-23 21:16:10 -04:00
Steven Rostedt 07d777fe8c tracing: Add percpu buffers for trace_printk()
Currently, trace_printk() uses a single buffer to write into
to calculate the size and format needed to save the trace. To
do this safely in an SMP environment, a spin_lock() is taken
to only allow one writer at a time to the buffer. But this could
also affect what is being traced, and add synchronization that
would not be there otherwise.

Ideally, using percpu buffers would be useful, but since trace_printk()
is only used in development, having per cpu buffers for something
never used is a waste of space. Thus, the use of the trace_bprintk()
format section is changed to be used for static fmts as well as dynamic ones.
Then at boot up, we can check if the section that holds the trace_printk
formats is non-empty, and if it does contain something, then we
know a trace_printk() has been added to the kernel. At this time
the trace_printk per cpu buffers are allocated. A check is also
done at module load time in case a module is added that contains a
trace_printk().

Once the buffers are allocated, they are never freed. If you use
a trace_printk() then you should know what you are doing.

A buffer is made for each type of context:

  normal
  softirq
  irq
  nmi

The context is checked and the appropriate buffer is used.
This allows for totally lockless usage of trace_printk(),
and they no longer even disable interrupts.

Requested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-04-23 21:15:55 -04:00
Steven Rostedt 348f0fc238 tracing: Fix regression with tracing_on
The change to make tracing_on affect only the ftrace ring buffer, caused
a bug where it wont affect any ring buffer. The problem was that the buffer
of the trace_array was passed to the write function and not the trace array
itself.

The trace_array can change the buffer when running a latency tracer. If this
happens, then the buffer being disabled may not be the buffer currently used
by ftrace. This will cause the tracing_on file to become useless.

The simple fix is to pass the trace_array to the write function instead of
the buffer. Then the actual buffer may be changed.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-04-16 15:41:28 -04:00
Steven Rostedt 12b5da349a tracing: Fix ent_size in trace output
When reading the trace file, the records of each of the per_cpu buffers
are examined to find the next event to print out. At the point of looking
at the event, the size of the event is recorded. But if the first event is
chosen, the other events in the other CPU buffers will reset the event size
that is stored in the iterator descriptor, causing the event size passed to
the output functions to be incorrect.

In most cases this is not a problem, but for the case of stack traces, it
is. With the change to the stack tracing to record a dynamic number of
back traces, the output depends on the size of the entry instead of the
fixed 8 back traces. When the entry size is not correct, the back traces
would not be fully printed.

Note, reading from the per-cpu trace files were not affected.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-03-27 12:05:44 -04:00
Steven Rostedt b892e5c897 tracing: Keep NMI watchdog from triggering when dumping trace
As ftrace_dump() (called by ftrace_dump_on_oops) disables interrupts
as it dumps its output to the console, it can keep interrupts disabled
for long periods of time. This is likely to trigger the NMI watchdog,
and it can disrupt the output of critical data.

Add a touch_nmi_watchdog() to each event that is written to the screen
to keep the NMI watchdog from affecting the output.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-03-01 22:06:48 -05:00
Steven Rostedt 499e547057 tracing/ring-buffer: Only have tracing_on disable tracing buffers
As the ring-buffer code is being used by other facilities in the
kernel, having tracing_on file disable *all* buffers is not a desired
affect. It should only disable the ftrace buffers that are being used.

Move the code into the trace.c file and use the buffer disabling
for tracing_on() and tracing_off(). This way only the ftrace buffers
will be affected by them and other kernel utilities will not be
confused to why their output suddenly stopped.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-02-22 15:50:28 -05:00
Geunsik Lim 1e42e83fde ftrace: sched_switch plugin is deprecated
Actually, sched_switch function tracer is merged into wakeup/wakeup_rt
Update 'mini-HOWTO' for ftrace(Kernel function tracer).
If we want to trace "sched:sched_switch" to trace sched_switch func,
We may utilize event option.(e.g: trace-cmd list -e | grep sched)
This patch is based on Linux-3.3.rc2-SMP-PREEMPT

Link: http://lkml.kernel.org/r/1328695537-15081-1-git-send-email-geunsik.lim@gmail.com

Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Geunsik Lim <geunsik.lim@samsung.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-02-13 09:14:47 -05:00
Linus Torvalds 972b2c7199 Merge branch 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
* 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (165 commits)
  reiserfs: Properly display mount options in /proc/mounts
  vfs: prevent remount read-only if pending removes
  vfs: count unlinked inodes
  vfs: protect remounting superblock read-only
  vfs: keep list of mounts for each superblock
  vfs: switch ->show_options() to struct dentry *
  vfs: switch ->show_path() to struct dentry *
  vfs: switch ->show_devname() to struct dentry *
  vfs: switch ->show_stats to struct dentry *
  switch security_path_chmod() to struct path *
  vfs: prefer ->dentry->d_sb to ->mnt->mnt_sb
  vfs: trim includes a bit
  switch mnt_namespace ->root to struct mount
  vfs: take /proc/*/mounts and friends to fs/proc_namespace.c
  vfs: opencode mntget() mnt_set_mountpoint()
  vfs: spread struct mount - remaining argument of next_mnt()
  vfs: move fsnotify junk to struct mount
  vfs: move mnt_devname
  vfs: move mnt_list to struct mount
  vfs: switch pnode.h macros to struct mount *
  ...
2012-01-08 12:19:57 -08:00
Linus Torvalds 35b740e466 Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (106 commits)
  perf kvm: Fix copy & paste error in description
  perf script: Kill script_spec__delete
  perf top: Fix a memory leak
  perf stat: Introduce get_ratio_color() helper
  perf session: Remove impossible condition check
  perf tools: Fix feature-bits rework fallout, remove unused variable
  perf script: Add generic perl handler to process events
  perf tools: Use for_each_set_bit() to iterate over feature flags
  perf tools: Unify handling of features when writing feature section
  perf report: Accept fifos as input file
  perf tools: Moving code in some files
  perf tools: Fix out-of-bound access to struct perf_session
  perf tools: Continue processing header on unknown features
  perf tools: Improve macros for struct feature_ops
  perf: builtin-record: Document and check that mmap_pages must be a power of two.
  perf: builtin-record: Provide advice if mmap'ing fails with EPERM.
  perf tools: Fix truncated annotation
  perf script: look up thread using tid instead of pid
  perf tools: Look up thread names for system wide profiling
  perf tools: Fix comm for processes with named threads
  ...
2012-01-06 08:02:58 -08:00
Al Viro f4ae40a6a5 switch debugfs to umode_t
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:54:56 -05:00
Paul E. McKenney a8eecf2248 trace: Allow ftrace_dump() to be called from modules
Add an EXPORT_SYMBOL_GPL() so that rcutorture can dump the trace buffer
upon detection of an RCU error.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2011-12-11 10:31:25 -08:00
Steven Rostedt 39eaf7ef88 tracing: Add entries in buffer and total entries to default output header
Knowing the number of event entries in the ring buffer compared
to the total number that were written is useful information. The
latency format gives this information and there's no reason that the
default format does not.

This information is now added to the default header, along with the
number of online CPUs:

 # tracer: nop
 #
 # entries-in-buffer/entries-written: 159836/64690869   #P:4
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
           <idle>-0     [000] ...2    49.442971: local_touch_nmi <-cpu_idle
           <idle>-0     [000] d..2    49.442973: enter_idle <-cpu_idle
           <idle>-0     [000] d..2    49.442974: atomic_notifier_call_chain <-enter_idle
           <idle>-0     [000] d..2    49.442976: __atomic_notifier_call_chain <-atomic_notifier

The above shows that the trace contains 159836 entries, but
64690869 were written. One could figure out that there were
64531033 entries that were dropped.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-11-17 11:10:43 -05:00
Steven Rostedt 77271ce4b2 tracing: Add irq, preempt-count and need resched info to default trace output
People keep asking how to get the preempt count, irq, and need resched info
and we keep telling them to enable the latency format. Some developers think
that traces without this info is completely useless, and for a lot of tasks
it is useless.

The first option was to enable the latency trace as the default format, but
the header for the latency format is pretty useless for most tracers and
it also does the timestamp in straight microseconds from the time the trace
started. This is sometimes more difficult to read as the default trace is
seconds from the start of boot up.

Latency format:

 # tracer: nop
 #
 # nop latency trace v1.1.5 on 3.2.0-rc1-test+
 # --------------------------------------------------------------------
 # latency: 0 us, #159771/64234230, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:4)
 #    -----------------
 #    | task: -0 (uid:0 nice:0 policy:0 rt_prio:0)
 #    -----------------
 #
 #                  _------=> CPU#
 #                 / _-----=> irqs-off
 #                | / _----=> need-resched
 #                || / _---=> hardirq/softirq
 #                ||| / _--=> preempt-depth
 #                |||| /     delay
 #  cmd     pid   ||||| time  |   caller
 #     \   /      |||||  \    |   /
 migratio-6       0...2 41778231us+: rcu_note_context_switch <-__schedule
 migratio-6       0...2 41778233us : trace_rcu_utilization <-rcu_note_context_switch
 migratio-6       0...2 41778235us+: rcu_sched_qs <-rcu_note_context_switch
 migratio-6       0d..2 41778236us+: rcu_preempt_qs <-rcu_note_context_switch
 migratio-6       0...2 41778238us : trace_rcu_utilization <-rcu_note_context_switch
 migratio-6       0...2 41778239us+: debug_lockdep_rcu_enabled <-__schedule

default format:

 # tracer: nop
 #
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
      migration/0-6     [000]    50.025810: rcu_note_context_switch <-__schedule
      migration/0-6     [000]    50.025812: trace_rcu_utilization <-rcu_note_context_switch
      migration/0-6     [000]    50.025813: rcu_sched_qs <-rcu_note_context_switch
      migration/0-6     [000]    50.025815: rcu_preempt_qs <-rcu_note_context_switch
      migration/0-6     [000]    50.025817: trace_rcu_utilization <-rcu_note_context_switch
      migration/0-6     [000]    50.025818: debug_lockdep_rcu_enabled <-__schedule
      migration/0-6     [000]    50.025820: debug_lockdep_rcu_enabled <-__schedule

The latency format header has latency information that is pretty meaningless
for most tracers. Although some of the header is useful, and we can add that
later to the default format as well.

What is really useful with the latency format is the irqs-off, need-resched
hard/softirq context and the preempt count.

This commit adds the option irq-info which is on by default that adds this
information:

 # tracer: nop
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
           <idle>-0     [000] d..2    49.309305: cpuidle_get_driver <-cpuidle_idle_call
           <idle>-0     [000] d..2    49.309307: mwait_idle <-cpu_idle
           <idle>-0     [000] d..2    49.309309: need_resched <-mwait_idle
           <idle>-0     [000] d..2    49.309310: test_ti_thread_flag <-need_resched
           <idle>-0     [000] d..2    49.309312: trace_power_start.constprop.13 <-mwait_idle
           <idle>-0     [000] d..2    49.309313: trace_cpu_idle <-mwait_idle
           <idle>-0     [000] d..2    49.309315: need_resched <-mwait_idle

If a user wants the old format, they can disable the 'irq-info' option:

 # tracer: nop
 #
 #           TASK-PID   CPU#      TIMESTAMP  FUNCTION
 #              | |       |          |         |
           <idle>-0     [000]     49.309305: cpuidle_get_driver <-cpuidle_idle_call
           <idle>-0     [000]     49.309307: mwait_idle <-cpu_idle
           <idle>-0     [000]     49.309309: need_resched <-mwait_idle
           <idle>-0     [000]     49.309310: test_ti_thread_flag <-need_resched
           <idle>-0     [000]     49.309312: trace_power_start.constprop.13 <-mwait_idle
           <idle>-0     [000]     49.309313: trace_cpu_idle <-mwait_idle
           <idle>-0     [000]     49.309315: need_resched <-mwait_idle

Requested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-11-17 09:58:48 -05:00
Ingo Molnar efc96737bd Merge branch 'tip/perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into perf/core 2011-11-11 08:19:37 +01:00
Jiri Olsa 7e9a49ef54 tracing/latency: Fix header output for latency tracers
In case the the graph tracer (CONFIG_FUNCTION_GRAPH_TRACER) or even the
function tracer (CONFIG_FUNCTION_TRACER) are not set, the latency tracers
do not display proper latency header.

The involved/fixed latency tracers are:
        wakeup_rt
        wakeup
        preemptirqsoff
        preemptoff
        irqsoff

The patch adds proper handling of tracer configuration options for latency
tracers, and displaying correct header info accordingly.

* The current output (for wakeup tracer) with both graph and function
  tracers disabled is:

  # tracer: wakeup
  #
    <idle>-0       0d.h5    1us+:      0:120:R   + [000]     7:  0:R watchdog/0
    <idle>-0       0d.h5    3us+: ttwu_do_activate.clone.1 <-try_to_wake_up
    ...

* The fixed output is:

  # tracer: wakeup
  #
  # wakeup latency trace v1.1.5 on 3.1.0-tip+
  # --------------------------------------------------------------------
  # latency: 55 us, #4/4, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
  #    -----------------
  #    | task: migration/0-6 (uid:0 nice:0 policy:1 rt_prio:99)
  #    -----------------
  #
  #                  _------=> CPU#
  #                 / _-----=> irqs-off
  #                | / _----=> need-resched
  #                || / _---=> hardirq/softirq
  #                ||| / _--=> preempt-depth
  #                |||| /     delay
  #  cmd     pid   ||||| time  |   caller
  #     \   /      |||||  \    |   /
       cat-1129    0d..4    1us :   1129:120:R   + [000]     6:  0:R migration/0
       cat-1129    0d..4    2us+: ttwu_do_activate.clone.1 <-try_to_wake_up

* The current output (for wakeup tracer) with only function
  tracer enabled is:

  # tracer: wakeup
  #
       cat-1140    0d..4    1us+:   1140:120:R   + [000]     6:  0:R migration/0
       cat-1140    0d..4    2us : ttwu_do_activate.clone.1 <-try_to_wake_up

* The fixed output is:
  # tracer: wakeup
  #
  # wakeup latency trace v1.1.5 on 3.1.0-tip+
  # --------------------------------------------------------------------
  # latency: 207 us, #109/109, CPU#1 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:2)
  #    -----------------
  #    | task: watchdog/1-12 (uid:0 nice:0 policy:1 rt_prio:99)
  #    -----------------
  #
  #                  _------=> CPU#
  #                 / _-----=> irqs-off
  #                | / _----=> need-resched
  #                || / _---=> hardirq/softirq
  #                ||| / _--=> preempt-depth
  #                |||| /     delay
  #  cmd     pid   ||||| time  |   caller
  #     \   /      |||||  \    |   /
    <idle>-0       1d.h5    1us+:      0:120:R   + [001]    12:  0:R watchdog/1
    <idle>-0       1d.h5    3us : ttwu_do_activate.clone.1 <-try_to_wake_up

Link: http://lkml.kernel.org/r/20111107150849.GE1807@m.brq.redhat.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-11-07 13:48:35 -05:00
Linus Torvalds 7115e3fcf4 Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (121 commits)
  perf symbols: Increase symbol KSYM_NAME_LEN size
  perf hists browser: Refuse 'a' hotkey on non symbolic views
  perf ui browser: Use libslang to read keys
  perf tools: Fix tracing info recording
  perf hists browser: Elide DSO column when it is set to just one DSO, ditto for threads
  perf hists: Don't consider filtered entries when calculating column widths
  perf hists: Don't decay total_period for filtered entries
  perf hists browser: Honour symbol_conf.show_{nr_samples,total_period}
  perf hists browser: Do not exit on tab key with single event
  perf annotate browser: Don't change selection line when returning from callq
  perf tools: handle endianness of feature bitmap
  perf tools: Add prelink suggestion to dso update message
  perf script: Fix unknown feature comment
  perf hists browser: Apply the dso and thread filters when merging new batches
  perf hists: Move the dso and thread filters from hist_browser
  perf ui browser: Honour the xterm colors
  perf top tui: Give color hints just on the percentage, like on --stdio
  perf ui browser: Make the colors configurable and change the defaults
  perf tui: Remove unneeded call to newtCls on startup
  perf hists: Don't format the percentage on hist_entry__snprintf
  ...

Fix up conflicts in arch/x86/kernel/kprobes.c manually.

Ingo's tree did the insane "add volatile to const array", which just
doesn't make sense ("volatile const"?).  But we could remove the const
*and* make the array volatile to make doubly sure that gcc doesn't
optimize it away..

Also fix up kernel/trace/ring_buffer.c non-data-conflicts manually: the
reader_lock has been turned into a raw lock by the core locking merge,
and there was a new user of it introduced in this perf core merge.  Make
sure that new use also uses the raw accessor functions.
2011-10-26 17:03:38 +02:00
Steven Rostedt 436fc28026 tracing: Fix returning of duplicate data after EOF in trace_pipe_raw
The trace_pipe_raw handler holds a cached page from the time the file
is opened to the time it is closed. The cached page is used to handle
the case of the user space buffer being smaller than what was read from
the ring buffer. The left over buffer is held in the cache so that the
next read will continue where the data left off.

After EOF is returned (no more data in the buffer), the index of
the cached page is set to zero. If a user app reads the page again
after EOF, the check in the buffer will see that the cached page
is less than page size and will return the cached page again. This
will cause reading the trace_pipe_raw again after EOF to return
duplicate data, making the output look like the time went backwards
but instead data is just repeated.

The fix is to not reset the index right after all data is read
from the cache, but to reset it after all data is read and more
data exists in the ring buffer.

Cc: stable <stable@kernel.org>
Reported-by: Jeremy Eder <jeder@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-10-14 10:44:25 -04:00
Geunsik Lim 9b5f8b31af ftrace: Fix README to state tracing_on to start/stop tracing
tracing_enabled option is deprecated.
To start/stop tracing, write to /sys/kernel/debug/tracing/tracing_on
without tracing_enabled. This patch is based on Linux 3.1.0-rc1

Signed-off-by: Geunsik Lim <geunsik.lim@samsung.com>
Link: http://lkml.kernel.org/r/1313127022-23830-1-git-send-email-leemgs1@gmail.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-10-14 10:41:33 -04:00
Steven Rostedt d696b58ca2 tracing: Do not allocate buffer for trace_marker
When doing intense tracing, the kmalloc inside trace_marker can
introduce side effects to what is being traced.

As trace_marker() is used by userspace to inject data into the
kernel ring buffer, it needs to do so with the least amount
of intrusion to the operations of the kernel or the user space
application.

As the ring buffer is designed to write directly into the buffer
without the need to make a temporary buffer, and userspace already
went through the hassle of knowing how big the write will be,
we can simply pin the userspace pages and write the data directly
into the buffer. This improves the impact of tracing via trace_marker
tremendously!

Thanks to Peter Zijlstra and Thomas Gleixner for pointing out the
use of get_user_pages_fast() and kmap_atomic().

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-10-11 09:13:53 -04:00
Steven Rostedt e0a413f619 tracing: Warn on output if the function tracer was found corrupted
As the function tracer is very intrusive, lots of self checks are
performed on the tracer and if something is found to be strange
it will shut itself down keeping it from corrupting the rest of the
kernel. This shutdown may still allow functions to be traced, as the
tracing only stops new modifications from happening. Trying to stop
the function tracer itself can cause more harm as it requires code
modification.

Although a WARN_ON() is executed, a user may not notice it. To help
the user see that something isn't right with the tracing of the system
a big warning is added to the output of the tracer that lets the user
know that their data may be incomplete.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-10-11 09:13:25 -04:00
Steven Rostedt 6249687f76 tracing: Add a counter clock for those that do not trust clocks
When debugging tight race conditions, it can be helpful to have a
synchronized tracing method. Although in most cases the global clock
provides this functionality, if timings is not the issue, it is more
comforting to know that the order of events really happened in a precise
order.

Instead of using a clock, add a "counter" that is simply an incrementing
atomic 64bit counter that orders the events as they are perceived to
happen.

The trace_clock_counter() is added from the attempt by Peter Zijlstra
trying to convert the trace_clock_global() to it. I took Peter's counter
code and made trace_clock_counter() instead, and added it to the choice
of clocks. Just echo counter > /debug/tracing/trace_clock to activate
it.

Requested-by: Thomas Gleixner <tglx@linutronix.de>
Requested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-By: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-09-19 11:35:58 -04:00
Thomas Gleixner 5389f6fad2 locking, tracing: Annotate tracing locks as raw
The tracing locks can be taken in atomic context and therefore
cannot be preempted on -rt - annotate it.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-09-13 11:11:52 +02:00
Vaibhav Nagarnaik c64e148a3b trace: Add ring buffer stats to measure rate of events
The stats file under per_cpu folder provides the number of entries,
overruns and other statistics about the CPU ring buffer. However, the
numbers do not provide any indication of how full the ring buffer is in
bytes compared to the overall size in bytes. Also, it is helpful to know
the rate at which the cpu buffer is filling up.

This patch adds an entry "bytes: " in printed stats for per_cpu ring
buffer which provides the actual bytes consumed in the ring buffer. This
field includes the number of bytes used by recorded events and the
padding bytes added when moving the tail pointer to next page.

It also adds the following time stamps:
"oldest event ts:" - the oldest timestamp in the ring buffer
"now ts:"  - the timestamp at the time of reading

The field "now ts" provides a consistent time snapshot to the userspace
when being read. This is read from the same trace clock used by tracing
event timestamps.

Together, these values provide the rate at which the buffer is filling
up, from the formula:
bytes / (now_ts - oldest_event_ts)

Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Link: http://lkml.kernel.org/r/1313531179-9323-3-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-08-30 12:27:45 -04:00
Vaibhav Nagarnaik f81ab074c3 trace: Add a new readonly entry to report total buffer size
The current file "buffer_size_kb" reports the size of per-cpu buffer and
not the overall memory allocated which could be misleading. A new file
"buffer_total_size_kb" adds up all the enabled CPU buffer sizes and
reports it. This is only a readonly entry.

Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Link: http://lkml.kernel.org/r/1313531179-9323-2-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-08-30 12:27:44 -04:00
Steven Rostedt 4a9bd3f134 tracing: Have dynamic size event stack traces
Currently the stack trace per event in ftace is only 8 frames.
This can be quite limiting and sometimes useless. Especially when
the "ignore frames" is wrong and we also use up stack frames for
the event processing itself.

Change this to be dynamic by adding a percpu buffer that we can
write a large stack frame into and then copy into the ring buffer.

For interrupts and NMIs that come in while another event is being
process, will only get to use the 8 frame stack. That should be enough
as the task that it interrupted will have the full stack frame anyway.

Requested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-07-14 16:36:53 -04:00
Masami Hiramatsu 1fd8df2c39 tracing/kprobes: Fix kprobe-tracer to support stack trace
Fix to support kernel stack trace correctly on kprobe-tracer.
Since the execution path of kprobe-based dynamic events is different
from other tracepoint-based events, normal ftrace_trace_stack() doesn't
work correctly. To fix that, this introduces ftrace_trace_stack_regs()
which traces stack via pt_regs instead of current stack register.

e.g.

 # echo p schedule+4 > /sys/kernel/debug/tracing/kprobe_events
 # echo 1 > /sys/kernel/debug/tracing/options/stacktrace
 # echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
 # head -n 20 /sys/kernel/debug/tracing/trace
            bash-2968  [000] 10297.050245: p_schedule_4: (schedule+0x4/0x4ca)
            bash-2968  [000] 10297.050247: <stack trace>
 => schedule_timeout
 => n_tty_read
 => tty_read
 => vfs_read
 => sys_read
 => system_call_fastpath
     kworker/0:1-2940  [000] 10297.050265: p_schedule_4: (schedule+0x4/0x4ca)
     kworker/0:1-2940  [000] 10297.050266: <stack trace>
 => worker_thread
 => kthread
 => kernel_thread_helper
            sshd-1132  [000] 10297.050365: p_schedule_4: (schedule+0x4/0x4ca)
            sshd-1132  [000] 10297.050365: <stack trace>
 => sysret_careful

Note: Even with this fix, the first entry will be skipped
if the probe is put on the function entry area before
the frame pointer is set up (usually, that is 4 bytes
 (push %bp; mov %sp %bp) on x86), because stack unwinder
depends on the frame pointer.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@gmail.com>
Link: http://lkml.kernel.org/r/20110608070934.17777.17116.stgit@fedora15
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-06-14 22:48:53 -04:00
Peter Huewe 22fe9b54d8 tracing: Convert to kstrtoul_from_user
This patch replaces the code for getting an unsigned long from a
userspace buffer by a simple call to kstroul_from_user.
This makes it easier to read and less error prone.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Link: http://lkml.kernel.org/r/1307476707-14762-1-git-send-email-peterhuewe@gmx.de
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-06-14 22:48:50 -04:00
Jiri Olsa f56e7f8efb tracing, function: Fix trace header to follow context-info option
The header display of function tracer does not follow
the context-info option, so field names are displayed even
if this option is off.

Added check for TRACE_ITER_CONTEXT_INFO trace_flags.

With following commands:
	# echo function > ./current_tracer
	# echo 0 > options/context-info
	# cat trace

This is what it looked like before:
# tracer: function
#
#           TASK-PID    CPU#    TIMESTAMP  FUNCTION
#              | |       |          |         |
add_preempt_count <-schedule
rcu_note_context_switch <-schedule
...

This is what it looks like now:
# tracer: function
#
_raw_spin_unlock_irqrestore <-hrtimer_try_to_cancel
...

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1307113131-10045-4-git-send-email-jolsa@redhat.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-06-14 22:48:48 -04:00
Steven Rostedt cf30cf67d6 tracing: Add disable_on_free option
Add a trace option to disable tracing on free. When this option is
set, a write into the free_buffer file will not only shrink the
ring buffer down to zero, but it will also disable tracing.

Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-06-14 22:48:45 -04:00
Vaibhav Nagarnaik 4f271a2a60 tracing: Add a proc file to stop tracing and free buffer
The proc file entry buffer_size_kb is used to set the size of tracing
buffer. The memory to expand the buffer size is kernel memory. Consider
a use case where tracing is handled by a user space utility, which acts
as a gate keeper for tracing requests. In an OOM condition, tracing is
considered a low priority task and if the utility gets killed the ring
buffer memory cannot be released back to the kernel.

This patch adds a proc file called "free_buffer" whose purpose is to
stop tracing and free up the ring buffer when it is closed.

The user space process can then set the desired size in buffer_size_kb
file and open the fd to the "free_buffer" file. Under OOM condition, if
the process gets killed, the kernel closes the file descriptor. The
release handler stops the tracing and releases the kernel memory
automatically.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Link: http://lkml.kernel.org/r/1308012717-11148-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-06-14 22:48:37 -04:00
Vaibhav Nagarnaik 7ea5906405 tracing: Use NUMA allocation for per-cpu ring buffer pages
The tracing ring buffer is a group of per-cpu ring buffers where
allocation and logging is done on a per-cpu basis. The events that are
generated on a particular CPU are logged in the corresponding buffer.
This is to provide wait-free writes between CPUs and good NUMA node
locality while accessing the ring buffer.

However, the allocation routines consider NUMA locality only for buffer
page metadata and not for the actual buffer page. This causes the pages
to be allocated on the NUMA node local to the CPU where the allocation
routine is running at the time.

This patch fixes the problem by using a NUMA node specific allocation
routine so that the pages are allocated from a NUMA node local to the
logging CPU.

I tested with the getuid_microbench from autotest. It is a simple binary
that calls getuid() in a loop and measures the average time for the
syscall to complete. The following command was used to test:
$ getuid_microbench 1000000

Compared the numbers found on kernel with and without this patch and
found that logging latency decreases by 30-50 ns/call.
tracing with non-NUMA allocation - 569 ns/call
tracing with NUMA allocation     - 512 ns/call

Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Link: http://lkml.kernel.org/r/1304470602-20366-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-06-14 22:04:39 -04:00
Vaibhav Nagarnaik e7e2ee89a9 tracing: Schedule a delayed work to call wakeup()
In using syscall tracing by concurrent processes, the wakeup() that is
called in the event commit function causes contention on the spin lock
of the waitqueue. I enabled sys_enter_getuid and sys_exit_getuid
tracepoints, and by running getuid_microbench from autotest in parallel
I found that the contention causes exponential latency increase in the
tracing path.

The autotest binary getuid_microbench calls getuid() in a tight loop for
the given number of iterations and measures the average time required to
complete a single invocation of syscall.

The patch schedules a delayed work after 2 ms once an event commit calls
to wake up the trace wait_queue. This removes the delay caused by
contention on spin lock in wakeup() and amortizes the wakeup() calls
scheduled over the 2 ms period.

In the following example, the script enables the sys_enter_getuid and
sys_exit_getuid tracepoints and runs the getuid_microbench in parallel
with the given number of processes. The output clearly shows the latency
increase caused by contentions.

$ ~/getuid.sh 1
1000000 calls in 0.720974253 s (720.974253 ns/call)

$ ~/getuid.sh 2
1000000 calls in 1.166457554 s (1166.457554 ns/call)
1000000 calls in 1.168933765 s (1168.933765 ns/call)

$ ~/getuid.sh 3
1000000 calls in 1.783827516 s (1783.827516 ns/call)
1000000 calls in 1.795553270 s (1795.553270 ns/call)
1000000 calls in 1.796493376 s (1796.493376 ns/call)

$ ~/getuid.sh 4
1000000 calls in 4.483041796 s (4483.041796 ns/call)
1000000 calls in 4.484165388 s (4484.165388 ns/call)
1000000 calls in 4.484850762 s (4484.850762 ns/call)
1000000 calls in 4.485643576 s (4485.643576 ns/call)

$ ~/getuid.sh 5
1000000 calls in 6.497521653 s (6497.521653 ns/call)
1000000 calls in 6.502000236 s (6502.000236 ns/call)
1000000 calls in 6.501709115 s (6501.709115 ns/call)
1000000 calls in 6.502124100 s (6502.124100 ns/call)
1000000 calls in 6.502936358 s (6502.936358 ns/call)

After the patch, the latencies scale better.
1000000 calls in 0.728720455 s (728.720455 ns/call)

1000000 calls in 0.842782857 s (842.782857 ns/call)
1000000 calls in 0.883803135 s (883.803135 ns/call)

1000000 calls in 0.902077764 s (902.077764 ns/call)
1000000 calls in 0.902838202 s (902.838202 ns/call)
1000000 calls in 0.908896885 s (908.896885 ns/call)

1000000 calls in 0.932523515 s (932.523515 ns/call)
1000000 calls in 0.958009672 s (958.009672 ns/call)
1000000 calls in 0.986188020 s (986.188020 ns/call)
1000000 calls in 0.989771102 s (989.771102 ns/call)

1000000 calls in 0.933518391 s (933.518391 ns/call)
1000000 calls in 0.958897947 s (958.897947 ns/call)
1000000 calls in 1.031038897 s (1031.038897 ns/call)
1000000 calls in 1.089516025 s (1089.516025 ns/call)
1000000 calls in 1.141998347 s (1141.998347 ns/call)

Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1305059241-7629-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-06-14 21:59:41 -04:00
Ingo Molnar 932fed4e2e Merge commit 'v2.6.39-rc7' into perf/core
Merge reason: pull in the latest fixes.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-05-10 17:05:45 +02:00
Arjan van de Ven a3a4a5acd3 Regression: partial revert "tracing: Remove lock_depth from event entry"
This partially reverts commit e6e1e25935.

That commit changed the structure layout of the trace structure, which
in turn broke PowerTOP (1.9x generation) quite badly.

I appreciate not wanting to expose the variable in question, and
PowerTOP was not using it, so I've replaced the variable with just a
padding field - that way if in the future a new field is needed it can
just use this padding field.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-05-06 13:20:59 -07:00
Ingo Molnar 32673822e4 Merge branch 'tip/perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/core
Conflicts:
	include/linux/perf_event.h

Merge reason: pick up the latest jump-label enhancements, they are cooked ready.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-27 10:40:21 +02:00
Jiri Olsa ee5e51f51b tracing: Avoid soft lockup in trace_pipe
running following commands:

  # enable the binary option
  echo 1 > ./options/bin
  # disable context info option
  echo 0 > ./options/context-info
  # tracing only events
  echo 1 > ./events/enable
  cat trace_pipe

plus forcing system to generate many tracing events,
is causing lockup (in NON preemptive kernels) inside
tracing_read_pipe function.

The issue is also easily reproduced by running ltp stress test.
(ftrace_stress_test.sh)

The reasons are:
 - bin/hex/raw output functions for events are set to
   trace_nop_print function, which prints nothing and
   returns TRACE_TYPE_HANDLED value
 - LOST EVENT trace do not handle trace_seq overflow

These reasons force the while loop in tracing_read_pipe
function never to break.

The attached patch fixies handling of lost event trace, and
changes trace_nop_print to print minimal info, which is needed
for the correct tracing_read_pipe processing.

v2 changes:
 - omit the cond_resched changes by trace_nop_print changes
 - WARN changed to WARN_ONCE and added info to be able
   to find out the culprit

v3 changes:
 - make more accurate patch comment

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
LKML-Reference: <20110325110518.GC1922@jolsa.brq.redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-04-04 12:18:24 -04:00
Lucas De Marchi 25985edced Fix common misspellings
Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
2011-03-31 11:26:23 -03:00
Steven Rostedt 4a0b1665db tracing: Fix irqoff selftest expanding max buffer
If the kernel command line declares a tracer "ftrace=sometracer" and
that tracer is either not defined or is enabled after irqsoff,
then the irqs off selftest will fail with the following error:

Testing tracer irqsoff:
------------[ cut here ]------------
WARNING: at /home/rostedt/work/autotest/nobackup/linux-test.git/kernel/trace/tra
ce.c:713 update_max_tr_single+0xfa/0x11b()
Hardware name:
Modules linked in:
Pid: 1, comm: swapper Not tainted 2.6.38-rc8-test #1
Call Trace:
 [<c0441d9d>] ? warn_slowpath_common+0x65/0x7a
 [<c049adb2>] ? update_max_tr_single+0xfa/0x11b
 [<c0441dc1>] ? warn_slowpath_null+0xf/0x13
 [<c049adb2>] ? update_max_tr_single+0xfa/0x11b
 [<c049e454>] ? stop_critical_timing+0x154/0x204
 [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
 [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
 [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
 [<c049e529>] ? time_hardirqs_on+0x25/0x28
 [<c0468bca>] ? trace_hardirqs_on_caller+0x18/0x12f
 [<c0468cec>] ? trace_hardirqs_on+0xb/0xd
 [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
 [<c049b6b8>] ? register_tracer+0xf8/0x1a3
 [<c14e93fe>] ? init_irqsoff_tracer+0xd/0x11
 [<c040115e>] ? do_one_initcall+0x71/0x121
 [<c14e93f1>] ? init_irqsoff_tracer+0x0/0x11
 [<c14ce3a9>] ? kernel_init+0x13a/0x1b6
 [<c14ce26f>] ? kernel_init+0x0/0x1b6
 [<c0403842>] ? kernel_thread_helper+0x6/0x10
---[ end trace e93713a9d40cd06c ]---
.. no entries found ..FAILED!

What happens is the "ftrace=..." will expand the ring buffer to its
default size (from its minimum size) but it will not expand the
max ring buffer (the ring buffer to store maximum latencies).
When the irqsoff test runs, it will call the ring buffer swap routine
that checks if the max ring buffer is the same size as the normal
ring buffer, and will fail if it is not. This causes the test to fail.

The solution is to expand the max ring buffer before running the self
test if the max ring buffer is used by that tracer and the normal ring
buffer is expanded. The max ring buffer should be shrunk again after
the test is done to save space.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-03-10 10:34:58 -05:00