tracing/kprobes: Fix probe offset to be unsigned

[pandora-kernel.git] / Documentation / trace / ftrace.txt

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 7bd27f0..355d0f1 100644 (file)
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -7,7 +7,6 @@ Copyright 2008 Red Hat Inc.
                (dual licensed under the GPL v2)
 Reviewers:   Elias Oltmanns, Randy Dunlap, Andrew Morton,
             John Kacur, and David Teigland.
                (dual licensed under the GPL v2)
 Reviewers:   Elias Oltmanns, Randy Dunlap, Andrew Morton,
             John Kacur, and David Teigland.

-

 Written for: 2.6.28-rc2
 
 Introduction
 Written for: 2.6.28-rc2
 
 Introduction


@@ -33,13 +32,26 @@ The File System
 Ftrace uses the debugfs file system to hold the control files as
 well as the files to display output.
 
 Ftrace uses the debugfs file system to hold the control files as
 well as the files to display output.
 

-To mount the debugfs system:
+When debugfs is configured into the kernel (which selecting any ftrace
+option will do) the directory /sys/kernel/debug will be created. To mount
+this directory, you can add to your /etc/fstab file:
+
+ debugfs       /sys/kernel/debug          debugfs defaults        0       0
+
+Or you can mount it at run time with:
+
+ mount -t debugfs nodev /sys/kernel/debug

 
 

-  # mkdir /debug
-  # mount -t debugfs nodev /debug
+For quicker access to that directory you may want to make a soft link to
+it:

 
 

-( Note: it is more common to mount at /sys/kernel/debug, but for
-  simplicity this document will use /debug)
+ ln -s /sys/kernel/debug /debug
+
+Any selected ftrace option will also create a directory called tracing
+within the debugfs. The rest of the document will assume that you are in
+the ftrace directory (cd /sys/kernel/debug/tracing) and will only concentrate
+on the files within that directory and not distract from the content with
+the extended "/sys/kernel/debug/tracing" path name.

 
 That's it! (assuming that you have ftrace configured into your kernel)
 
 
 That's it! (assuming that you have ftrace configured into your kernel)
 


@@ -73,26 +85,19 @@ of ftrace. Here is a list of some of the key files:
        This file holds the output of the trace in a human
        readable format (described below).
 
        This file holds the output of the trace in a human
        readable format (described below).
 

-  latency_trace:
-
-       This file shows the same trace but the information
-       is organized more to display possible latencies
-       in the system (described below).
-

   trace_pipe:
 
        The output is the same as the "trace" file but this
        file is meant to be streamed with live tracing.
   trace_pipe:
 
        The output is the same as the "trace" file but this
        file is meant to be streamed with live tracing.

-       Reads from this file will block until new data
-       is retrieved. Unlike the "trace" and "latency_trace"
-       files, this file is a consumer. This means reading
-       from this file causes sequential reads to display
-       more current data. Once data is read from this
-       file, it is consumed, and will not be read
-       again with a sequential read. The "trace" and
-       "latency_trace" files are static, and if the
-       tracer is not adding more data, they will display
-       the same information every time they are read.
+       Reads from this file will block until new data is
+       retrieved.  Unlike the "trace" file, this file is a
+       consumer. This means reading from this file causes
+       sequential reads to display more current data. Once
+       data is read from this file, it is consumed, and
+       will not be read again with a sequential read. The
+       "trace" file is static, and if the tracer is not
+       adding more data,they will display the same
+       information every time they are read.

 
   trace_options:
 
 
   trace_options:
 


@@ -105,10 +110,10 @@ of ftrace. Here is a list of some of the key files:
        Some of the tracers record the max latency.
        For example, the time interrupts are disabled.
        This time is saved in this file. The max trace
        Some of the tracers record the max latency.
        For example, the time interrupts are disabled.
        This time is saved in this file. The max trace

-       will also be stored, and displayed by either
-       "trace" or "latency_trace".  A new max trace will
-       only be recorded if the latency is greater than
-       the value in this file. (in microseconds)
+       will also be stored, and displayed by "trace".
+       A new max trace will only be recorded if the
+       latency is greater than the value in this
+       file. (in microseconds)

 
   buffer_size_kb:
 
 
   buffer_size_kb:
 


@@ -198,7 +203,7 @@ Here is the list of current tracers that may be configured.
        the trace with the longest max latency.
        See tracing_max_latency. When a new max is recorded,
        it replaces the old trace. It is best to view this
        the trace with the longest max latency.
        See tracing_max_latency. When a new max is recorded,
        it replaces the old trace. It is best to view this

-       trace via the latency_trace file.
+       trace with the latency-format option enabled.

 
   "preemptoff"
 
 
   "preemptoff"
 


@@ -295,8 +300,8 @@ the lowest priority thread (pid 0).
 Latency trace format
 --------------------
 
 Latency trace format
 --------------------
 

-For traces that display latency times, the latency_trace file
-gives somewhat more information to see why a latency happened.
+When the latency-format option is enabled, the trace file gives
+somewhat more information to see why a latency happened.

 Here is a typical trace.
 
 # tracer: irqsoff
 Here is a typical trace.
 
 # tracer: irqsoff


@@ -368,9 +373,10 @@ explains which is which.
 
 The above is mostly meaningful for kernel developers.
 
 
 The above is mostly meaningful for kernel developers.
 

-  time: This differs from the trace file output. The trace file output
-       includes an absolute timestamp. The timestamp used by the
-       latency_trace file is relative to the start of the trace.
+  time: When the latency-format option is enabled, the trace file
+       output includes a timestamp relative to the start of the
+       trace. This differs from the output when latency-format
+       is disabled, which includes an absolute timestamp.

 
   delay: This is just to help catch your eye a bit better. And
         needs to be fixed to be only relative to the same CPU.
 
   delay: This is just to help catch your eye a bit better. And
         needs to be fixed to be only relative to the same CPU.


@@ -389,18 +395,18 @@ trace_options
 The trace_options file is used to control what gets printed in
 the trace output. To see what is available, simply cat the file:
 
 The trace_options file is used to control what gets printed in
 the trace output. To see what is available, simply cat the file:
 

-  cat /debug/tracing/trace_options
+  cat trace_options

   print-parent nosym-offset nosym-addr noverbose noraw nohex nobin \
   noblock nostacktrace nosched-tree nouserstacktrace nosym-userobj
 
 To disable one of the options, echo in the option prepended with
 "no".
 
   print-parent nosym-offset nosym-addr noverbose noraw nohex nobin \
   noblock nostacktrace nosched-tree nouserstacktrace nosym-userobj
 
 To disable one of the options, echo in the option prepended with
 "no".
 

-  echo noprint-parent > /debug/tracing/trace_options
+  echo noprint-parent > trace_options

 
 To enable an option, leave off the "no".
 
 
 To enable an option, leave off the "no".
 

-  echo sym-offset > /debug/tracing/trace_options
+  echo sym-offset > trace_options

 
 Here are the available options:
 
 
 Here are the available options:
 


@@ -428,7 +434,8 @@ Here are the available options:
   sym-addr:
    bash-4000  [01]  1477.606694: simple_strtoul <c0339346>
 
   sym-addr:
    bash-4000  [01]  1477.606694: simple_strtoul <c0339346>
 

-  verbose - This deals with the latency_trace file.
+  verbose - This deals with the trace file when the
+            latency-format option is enabled.

 
     bash  4000 1 0 00000000 00010a95 [58127d26] 1720.415ms \
     (+0.000ms): simple_strtoul (strict_strtoul)
 
     bash  4000 1 0 00000000 00010a95 [58127d26] 1720.415ms \
     (+0.000ms): simple_strtoul (strict_strtoul)


@@ -460,7 +467,7 @@ Here are the available options:
                the app is no longer running
 
                The lookup is performed when you read
                the app is no longer running
 
                The lookup is performed when you read

-               trace,trace_pipe,latency_trace. Example:
+               trace,trace_pipe. Example:

 
                a.out-1623  [000] 40874.465068: /root/a.out[+0x480] <-/root/a.out[+0
 x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
 
                a.out-1623  [000] 40874.465068: /root/a.out[+0x480] <-/root/a.out[+0
 x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]


@@ -469,6 +476,11 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
               every scheduling event. Will add overhead if
               there's a lot of tasks running at once.
 
               every scheduling event. Will add overhead if
               there's a lot of tasks running at once.
 

+  latency-format - This option changes the trace. When
+                   it is enabled, the trace displays
+                   additional information about the
+                   latencies, as described in "Latency
+                   trace format".

 
 sched_switch
 ------------
 
 sched_switch
 ------------


@@ -476,11 +488,11 @@ sched_switch
 This tracer simply records schedule switches. Here is an example
 of how to use it.
 
 This tracer simply records schedule switches. Here is an example
 of how to use it.
 

- # echo sched_switch > /debug/tracing/current_tracer
- # echo 1 > /debug/tracing/tracing_enabled
+ # echo sched_switch > current_tracer
+ # echo 1 > tracing_enabled

  # sleep 1
  # sleep 1

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/trace
+ # echo 0 > tracing_enabled
+ # cat trace

 
 # tracer: sched_switch
 #
 
 # tracer: sched_switch
 #


@@ -583,13 +595,14 @@ new trace is saved.
 To reset the maximum, echo 0 into tracing_max_latency. Here is
 an example:
 
 To reset the maximum, echo 0 into tracing_max_latency. Here is
 an example:
 

- # echo irqsoff > /debug/tracing/current_tracer
- # echo 0 > /debug/tracing/tracing_max_latency
- # echo 1 > /debug/tracing/tracing_enabled
+ # echo irqsoff > current_tracer
+ # echo latency-format > trace_options
+ # echo 0 > tracing_max_latency
+ # echo 1 > tracing_enabled

  # ls -ltr
  [...]
  # ls -ltr
  [...]

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/latency_trace
+ # echo 0 > tracing_enabled
+ # cat trace

 # tracer: irqsoff
 #
 irqsoff latency trace v1.1.5 on 2.6.26
 # tracer: irqsoff
 #
 irqsoff latency trace v1.1.5 on 2.6.26


@@ -690,13 +703,14 @@ Like the irqsoff tracer, it records the maximum latency for
 which preemption was disabled. The control of preemptoff tracer
 is much like the irqsoff tracer.
 
 which preemption was disabled. The control of preemptoff tracer
 is much like the irqsoff tracer.
 

- # echo preemptoff > /debug/tracing/current_tracer
- # echo 0 > /debug/tracing/tracing_max_latency
- # echo 1 > /debug/tracing/tracing_enabled
+ # echo preemptoff > current_tracer
+ # echo latency-format > trace_options
+ # echo 0 > tracing_max_latency
+ # echo 1 > tracing_enabled

  # ls -ltr
  [...]
  # ls -ltr
  [...]

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/latency_trace
+ # echo 0 > tracing_enabled
+ # cat trace

 # tracer: preemptoff
 #
 preemptoff latency trace v1.1.5 on 2.6.26-rc8
 # tracer: preemptoff
 #
 preemptoff latency trace v1.1.5 on 2.6.26-rc8


@@ -837,13 +851,14 @@ tracer.
 Again, using this trace is much like the irqsoff and preemptoff
 tracers.
 
 Again, using this trace is much like the irqsoff and preemptoff
 tracers.
 

- # echo preemptirqsoff > /debug/tracing/current_tracer
- # echo 0 > /debug/tracing/tracing_max_latency
- # echo 1 > /debug/tracing/tracing_enabled
+ # echo preemptirqsoff > current_tracer
+ # echo latency-format > trace_options
+ # echo 0 > tracing_max_latency
+ # echo 1 > tracing_enabled

  # ls -ltr
  [...]
  # ls -ltr
  [...]

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/latency_trace
+ # echo 0 > tracing_enabled
+ # cat trace

 # tracer: preemptirqsoff
 #
 preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8
 # tracer: preemptirqsoff
 #
 preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8


@@ -999,12 +1014,13 @@ slightly differently than we did with the previous tracers.
 Instead of performing an 'ls', we will run 'sleep 1' under
 'chrt' which changes the priority of the task.
 
 Instead of performing an 'ls', we will run 'sleep 1' under
 'chrt' which changes the priority of the task.
 

- # echo wakeup > /debug/tracing/current_tracer
- # echo 0 > /debug/tracing/tracing_max_latency
- # echo 1 > /debug/tracing/tracing_enabled
+ # echo wakeup > current_tracer
+ # echo latency-format > trace_options
+ # echo 0 > tracing_max_latency
+ # echo 1 > tracing_enabled

  # chrt -f 5 sleep 1
  # chrt -f 5 sleep 1

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/latency_trace
+ # echo 0 > tracing_enabled
+ # cat trace

 # tracer: wakeup
 #
 wakeup latency trace v1.1.5 on 2.6.26-rc8
 # tracer: wakeup
 #
 wakeup latency trace v1.1.5 on 2.6.26-rc8


@@ -1114,11 +1130,11 @@ can be done from the debug file system. Make sure the
 ftrace_enabled is set; otherwise this tracer is a nop.
 
  # sysctl kernel.ftrace_enabled=1
 ftrace_enabled is set; otherwise this tracer is a nop.
 
  # sysctl kernel.ftrace_enabled=1

- # echo function > /debug/tracing/current_tracer
- # echo 1 > /debug/tracing/tracing_enabled
+ # echo function > current_tracer
+ # echo 1 > tracing_enabled

  # usleep 1
  # usleep 1

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/trace
+ # echo 0 > tracing_enabled
+ # cat trace

 # tracer: function
 #
 #           TASK-PID   CPU#    TIMESTAMP  FUNCTION
 # tracer: function
 #
 #           TASK-PID   CPU#    TIMESTAMP  FUNCTION


@@ -1155,7 +1171,7 @@ int trace_fd;
 [...]
 int main(int argc, char *argv[]) {
        [...]
 [...]
 int main(int argc, char *argv[]) {
        [...]

-       trace_fd = open("/debug/tracing/tracing_enabled", O_WRONLY);
+       trace_fd = open(tracing_file("tracing_enabled"), O_WRONLY);

        [...]
        if (condition_hit()) {
                write(trace_fd, "0", 1);
        [...]
        if (condition_hit()) {
                write(trace_fd, "0", 1);


@@ -1163,26 +1179,20 @@ int main(int argc, char *argv[]) {
        [...]
 }
 
        [...]
 }
 

-Note: Here we hard coded the path name. The debugfs mount is not
-guaranteed to be at /debug (and is more commonly at
-/sys/kernel/debug). For simple one time traces, the above is
-sufficent. For anything else, a search through /proc/mounts may
-be needed to find where the debugfs file-system is mounted.
-

 
 Single thread tracing
 ---------------------
 
 
 Single thread tracing
 ---------------------
 

-By writing into /debug/tracing/set_ftrace_pid you can trace a
+By writing into set_ftrace_pid you can trace a

 single thread. For example:
 
 single thread. For example:
 

-# cat /debug/tracing/set_ftrace_pid
+# cat set_ftrace_pid

 no pid
 no pid

-# echo 3111 > /debug/tracing/set_ftrace_pid
-# cat /debug/tracing/set_ftrace_pid
+# echo 3111 > set_ftrace_pid
+# cat set_ftrace_pid

 3111
 3111

-# echo function > /debug/tracing/current_tracer
-# cat /debug/tracing/trace | head
+# echo function > current_tracer
+# cat trace | head

  # tracer: function
  #
  #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
  # tracer: function
  #
  #           TASK-PID    CPU#    TIMESTAMP  FUNCTION


@@ -1193,8 +1203,8 @@ no pid
      yum-updatesd-3111  [003]  1637.254683: lock_hrtimer_base <-hrtimer_try_to_cancel
      yum-updatesd-3111  [003]  1637.254685: fget_light <-do_sys_poll
      yum-updatesd-3111  [003]  1637.254686: pipe_poll <-do_sys_poll
      yum-updatesd-3111  [003]  1637.254683: lock_hrtimer_base <-hrtimer_try_to_cancel
      yum-updatesd-3111  [003]  1637.254685: fget_light <-do_sys_poll
      yum-updatesd-3111  [003]  1637.254686: pipe_poll <-do_sys_poll

-# echo -1 > /debug/tracing/set_ftrace_pid
-# cat /debug/tracing/trace |head
+# echo -1 > set_ftrace_pid
+# cat trace |head

  # tracer: function
  #
  #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
  # tracer: function
  #
  #           TASK-PID    CPU#    TIMESTAMP  FUNCTION


@@ -1216,6 +1226,51 @@ something like this simple program:
 #include <fcntl.h>
 #include <unistd.h>
 
 #include <fcntl.h>
 #include <unistd.h>
 

+#define _STR(x) #x
+#define STR(x) _STR(x)
+#define MAX_PATH 256
+
+const char *find_debugfs(void)
+{
+       static char debugfs[MAX_PATH+1];
+       static int debugfs_found;
+       char type[100];
+       FILE *fp;
+
+       if (debugfs_found)
+               return debugfs;
+
+       if ((fp = fopen("/proc/mounts","r")) == NULL) {
+               perror("/proc/mounts");
+               return NULL;
+       }
+
+       while (fscanf(fp, "%*s %"
+                     STR(MAX_PATH)
+                     "s %99s %*s %*d %*d\n",
+                     debugfs, type) == 2) {
+               if (strcmp(type, "debugfs") == 0)
+                       break;
+       }
+       fclose(fp);
+
+       if (strcmp(type, "debugfs") != 0) {
+               fprintf(stderr, "debugfs not mounted");
+               return NULL;
+       }
+
+       debugfs_found = 1;
+
+       return debugfs;
+}
+
+const char *tracing_file(const char *file_name)
+{
+       static char trace_file[MAX_PATH+1];
+       snprintf(trace_file, MAX_PATH, "%s/%s", find_debugfs(), file_name);
+       return trace_file;
+}
+

 int main (int argc, char **argv)
 {
         if (argc < 1)
 int main (int argc, char **argv)
 {
         if (argc < 1)


@@ -1226,12 +1281,12 @@ int main (int argc, char **argv)
                 char line[64];
                 int s;
 
                 char line[64];
                 int s;
 

-                ffd = open("/debug/tracing/current_tracer", O_WRONLY);
+                ffd = open(tracing_file("current_tracer"), O_WRONLY);

                 if (ffd < 0)
                         exit(-1);
                 write(ffd, "nop", 3);
 
                 if (ffd < 0)
                         exit(-1);
                 write(ffd, "nop", 3);
 

-                fd = open("/debug/tracing/set_ftrace_pid", O_WRONLY);
+                fd = open(tracing_file("set_ftrace_pid"), O_WRONLY);

                 s = sprintf(line, "%d\n", getpid());
                 write(fd, line, s);
 
                 s = sprintf(line, "%d\n", getpid());
                 write(fd, line, s);
 


@@ -1383,22 +1438,22 @@ want, depending on your needs.
   tracing_cpu_mask file) or you might sometimes see unordered
   function calls while cpu tracing switch.
 
   tracing_cpu_mask file) or you might sometimes see unordered
   function calls while cpu tracing switch.
 

-       hide: echo nofuncgraph-cpu > /debug/tracing/trace_options
-       show: echo funcgraph-cpu > /debug/tracing/trace_options
+       hide: echo nofuncgraph-cpu > trace_options
+       show: echo funcgraph-cpu > trace_options

 
 - The duration (function's time of execution) is displayed on
   the closing bracket line of a function or on the same line
   than the current function in case of a leaf one. It is default
   enabled.
 
 
 - The duration (function's time of execution) is displayed on
   the closing bracket line of a function or on the same line
   than the current function in case of a leaf one. It is default
   enabled.
 

-       hide: echo nofuncgraph-duration > /debug/tracing/trace_options
-       show: echo funcgraph-duration > /debug/tracing/trace_options
+       hide: echo nofuncgraph-duration > trace_options
+       show: echo funcgraph-duration > trace_options

 
 - The overhead field precedes the duration field in case of
   reached duration thresholds.
 
 
 - The overhead field precedes the duration field in case of
   reached duration thresholds.
 

-       hide: echo nofuncgraph-overhead > /debug/tracing/trace_options
-       show: echo funcgraph-overhead > /debug/tracing/trace_options
+       hide: echo nofuncgraph-overhead > trace_options
+       show: echo funcgraph-overhead > trace_options

        depends on: funcgraph-duration
 
   ie:
        depends on: funcgraph-duration
 
   ie:


@@ -1427,8 +1482,8 @@ want, depending on your needs.
 - The task/pid field displays the thread cmdline and pid which
   executed the function. It is default disabled.
 
 - The task/pid field displays the thread cmdline and pid which
   executed the function. It is default disabled.
 

-       hide: echo nofuncgraph-proc > /debug/tracing/trace_options
-       show: echo funcgraph-proc > /debug/tracing/trace_options
+       hide: echo nofuncgraph-proc > trace_options
+       show: echo funcgraph-proc > trace_options

 
   ie:
 
 
   ie:
 


@@ -1451,8 +1506,8 @@ want, depending on your needs.
   system clock since it started. A snapshot of this time is
   given on each entry/exit of functions
 
   system clock since it started. A snapshot of this time is
   given on each entry/exit of functions
 

-       hide: echo nofuncgraph-abstime > /debug/tracing/trace_options
-       show: echo funcgraph-abstime > /debug/tracing/trace_options
+       hide: echo nofuncgraph-abstime > trace_options
+       show: echo funcgraph-abstime > trace_options

 
   ie:
 
 
   ie:
 


@@ -1549,7 +1604,7 @@ listed in:
 
    available_filter_functions
 
 
    available_filter_functions
 

- # cat /debug/tracing/available_filter_functions
+ # cat available_filter_functions

 put_prev_task_idle
 kmem_cache_create
 pick_next_task_rt
 put_prev_task_idle
 kmem_cache_create
 pick_next_task_rt


@@ -1561,12 +1616,12 @@ mutex_lock
 If I am only interested in sys_nanosleep and hrtimer_interrupt:
 
  # echo sys_nanosleep hrtimer_interrupt \
 If I am only interested in sys_nanosleep and hrtimer_interrupt:
 
  # echo sys_nanosleep hrtimer_interrupt \

-               > /debug/tracing/set_ftrace_filter
- # echo ftrace > /debug/tracing/current_tracer
- # echo 1 > /debug/tracing/tracing_enabled
+               > set_ftrace_filter
+ # echo ftrace > current_tracer
+ # echo 1 > tracing_enabled

  # usleep 1
  # usleep 1

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/trace
+ # echo 0 > tracing_enabled
+ # cat trace

 # tracer: ftrace
 #
 #           TASK-PID   CPU#    TIMESTAMP  FUNCTION
 # tracer: ftrace
 #
 #           TASK-PID   CPU#    TIMESTAMP  FUNCTION


@@ -1577,7 +1632,7 @@ If I am only interested in sys_nanosleep and hrtimer_interrupt:
 
 To see which functions are being traced, you can cat the file:
 
 
 To see which functions are being traced, you can cat the file:
 

- # cat /debug/tracing/set_ftrace_filter
+ # cat set_ftrace_filter

 hrtimer_interrupt
 sys_nanosleep
 
 hrtimer_interrupt
 sys_nanosleep
 


@@ -1597,7 +1652,7 @@ Note: It is better to use quotes to enclose the wild cards,
       otherwise the shell may expand the parameters into names
       of files in the local directory.
 
       otherwise the shell may expand the parameters into names
       of files in the local directory.
 

- # echo 'hrtimer_*' > /debug/tracing/set_ftrace_filter
+ # echo 'hrtimer_*' > set_ftrace_filter

 
 Produces:
 
 
 Produces:
 


@@ -1618,7 +1673,7 @@ Produces:
 
 Notice that we lost the sys_nanosleep.
 
 
 Notice that we lost the sys_nanosleep.
 

- # cat /debug/tracing/set_ftrace_filter
+ # cat set_ftrace_filter

 hrtimer_run_queues
 hrtimer_run_pending
 hrtimer_init
 hrtimer_run_queues
 hrtimer_run_pending
 hrtimer_init


@@ -1644,17 +1699,17 @@ To append to the filters, use '>>'
 To clear out a filter so that all functions will be recorded
 again:
 
 To clear out a filter so that all functions will be recorded
 again:
 

- # echo > /debug/tracing/set_ftrace_filter
- # cat /debug/tracing/set_ftrace_filter
+ # echo > set_ftrace_filter
+ # cat set_ftrace_filter

  #
 
 Again, now we want to append.
 
  #
 
 Again, now we want to append.
 

- # echo sys_nanosleep > /debug/tracing/set_ftrace_filter
- # cat /debug/tracing/set_ftrace_filter
+ # echo sys_nanosleep > set_ftrace_filter
+ # cat set_ftrace_filter

 sys_nanosleep
 sys_nanosleep

- # echo 'hrtimer_*' >> /debug/tracing/set_ftrace_filter
- # cat /debug/tracing/set_ftrace_filter
+ # echo 'hrtimer_*' >> set_ftrace_filter
+ # cat set_ftrace_filter

 hrtimer_run_queues
 hrtimer_run_pending
 hrtimer_init
 hrtimer_run_queues
 hrtimer_run_pending
 hrtimer_init


@@ -1677,7 +1732,7 @@ hrtimer_init_sleeper
 The set_ftrace_notrace prevents those functions from being
 traced.
 
 The set_ftrace_notrace prevents those functions from being
 traced.
 

- # echo '*preempt*' '*lock*' > /debug/tracing/set_ftrace_notrace
+ # echo '*preempt*' '*lock*' > set_ftrace_notrace

 
 Produces:
 
 
 Produces:
 


@@ -1767,13 +1822,13 @@ the effect on the tracing is different. Every read from
 trace_pipe is consumed. This means that subsequent reads will be
 different. The trace is live.
 
 trace_pipe is consumed. This means that subsequent reads will be
 different. The trace is live.
 

- # echo function > /debug/tracing/current_tracer
- # cat /debug/tracing/trace_pipe > /tmp/trace.out &
+ # echo function > current_tracer
+ # cat trace_pipe > /tmp/trace.out &

 [1] 4153
 [1] 4153

- # echo 1 > /debug/tracing/tracing_enabled
+ # echo 1 > tracing_enabled

  # usleep 1
  # usleep 1

- # echo 0 > /debug/tracing/tracing_enabled
- # cat /debug/tracing/trace
+ # echo 0 > tracing_enabled
+ # cat trace

 # tracer: function
 #
 #           TASK-PID   CPU#    TIMESTAMP  FUNCTION
 # tracer: function
 #
 #           TASK-PID   CPU#    TIMESTAMP  FUNCTION


@@ -1809,7 +1864,7 @@ number listed is the number of entries that can be recorded per
 CPU. To know the full size, multiply the number of possible CPUS
 with the number of entries.
 
 CPU. To know the full size, multiply the number of possible CPUS
 with the number of entries.
 

- # cat /debug/tracing/buffer_size_kb
+ # cat buffer_size_kb

 1408 (units kilobytes)
 
 Note, to modify this, you must have tracing completely disabled.
 1408 (units kilobytes)
 
 Note, to modify this, you must have tracing completely disabled.


@@ -1817,18 +1872,18 @@ To do that, echo "nop" into the current_tracer. If the
 current_tracer is not set to "nop", an EINVAL error will be
 returned.
 
 current_tracer is not set to "nop", an EINVAL error will be
 returned.
 

- # echo nop > /debug/tracing/current_tracer
- # echo 10000 > /debug/tracing/buffer_size_kb
- # cat /debug/tracing/buffer_size_kb
+ # echo nop > current_tracer
+ # echo 10000 > buffer_size_kb
+ # cat buffer_size_kb

 10000 (units kilobytes)
 
 The number of pages which will be allocated is limited to a
 percentage of available memory. Allocating too much will produce
 an error.
 
 10000 (units kilobytes)
 
 The number of pages which will be allocated is limited to a
 percentage of available memory. Allocating too much will produce
 an error.
 

- # echo 1000000000000 > /debug/tracing/buffer_size_kb
+ # echo 1000000000000 > buffer_size_kb

 -bash: echo: write error: Cannot allocate memory
 -bash: echo: write error: Cannot allocate memory

- # cat /debug/tracing/buffer_size_kb
+ # cat buffer_size_kb

 85
 
 -----------
 85
 
 -----------