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debugfs: Fix terminology inconsistency of dir name to mount debugfs filesystem.

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Many developers use "/debug/" or "/debugfs/" or "/sys/kernel/debug/"
directory name to mount debugfs filesystem for ftrace according to
./Documentation/tracers/ftrace.txt file.

And, three directory names(ex:/debug/, /debugfs/, /sys/kernel/debug/) is
existed in kernel source like ftrace, DRM, Wireless, Documentation,
Network[sky2]files to mount debugfs filesystem.

debugfs means debug filesystem for debugging easy to use by greg kroah
hartman. "/sys/kernel/debug/" name is suitable as directory name
of debugfs filesystem.
- debugfs related reference: http://lwn.net/Articles/334546/

Fix inconsistency of directory name to mount debugfs filesystem.

* From Steven Rostedt
  - find_debugfs() and tracing_files() in this patch.

Signed-off-by: GeunSik Lim <geunsik.lim@samsung.com>
Acked-by     : Inaky Perez-Gonzalez <inaky@linux.intel.com>
Reviewed-by  : Steven Rostedt <rostedt@goodmis.org>
Reviewed-by  : James Smart <james.smart@emulex.com>
CC: Jiri Kosina <trivial@kernel.org>
CC: David Airlie <airlied@linux.ie>
CC: Peter Osterlund <petero2@telia.com>
CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
CC: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
CC: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
GeunSik Lim
2009-06-02 15:01:37 +09:00
committed by Greg Kroah-Hartman
parent 1b713e0050
commit 156f5a7801
20 changed files with 238 additions and 191 deletions
Download Patch File Download Diff File Expand all files Collapse all files

233
Documentation/trace/ftrace.txt
View File

@@ -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.
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.
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:
# mkdir /debug
# mount -t debugfs nodev /debug
debugfs /sys/kernel/debug debugfs defaults 0 0
( Note: it is more common to mount at /sys/kernel/debug, but for
simplicity this document will use /debug)
Or you can mount it at run time with:
mount -t debugfs nodev /sys/kernel/debug
For quicker access to that directory you may want to make a soft link to
it:
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)
@@ -389,18 +401,18 @@ 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:
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".
echo noprint-parent > /debug/tracing/trace_options
echo noprint-parent > trace_options
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:
@@ -476,11 +488,11 @@ sched_switch
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
# echo 0 > /debug/tracing/tracing_enabled
# cat /debug/tracing/trace
# echo 0 > tracing_enabled
# cat trace
# tracer: sched_switch
#
@@ -583,13 +595,13 @@ new trace is saved.
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 0 > tracing_max_latency
# echo 1 > tracing_enabled
# ls -ltr
[...]
# echo 0 > /debug/tracing/tracing_enabled
# cat /debug/tracing/latency_trace
# echo 0 > tracing_enabled
# cat latency_trace
# tracer: irqsoff
#
irqsoff latency trace v1.1.5 on 2.6.26
@@ -690,13 +702,13 @@ 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.
# echo preemptoff > /debug/tracing/current_tracer
# echo 0 > /debug/tracing/tracing_max_latency
# echo 1 > /debug/tracing/tracing_enabled
# echo preemptoff > current_tracer
# echo 0 > tracing_max_latency
# echo 1 > tracing_enabled
# ls -ltr
[...]
# echo 0 > /debug/tracing/tracing_enabled
# cat /debug/tracing/latency_trace
# echo 0 > tracing_enabled
# cat latency_trace
# tracer: preemptoff
#
preemptoff latency trace v1.1.5 on 2.6.26-rc8
@@ -837,13 +849,13 @@ tracer.
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 0 > tracing_max_latency
# echo 1 > tracing_enabled
# ls -ltr
[...]
# echo 0 > /debug/tracing/tracing_enabled
# cat /debug/tracing/latency_trace
# echo 0 > tracing_enabled
# cat latency_trace
# tracer: preemptirqsoff
#
preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8
@@ -999,12 +1011,12 @@ 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.
# echo wakeup > /debug/tracing/current_tracer
# echo 0 > /debug/tracing/tracing_max_latency
# echo 1 > /debug/tracing/tracing_enabled
# echo wakeup > current_tracer
# echo 0 > tracing_max_latency
# echo 1 > tracing_enabled
# chrt -f 5 sleep 1
# echo 0 > /debug/tracing/tracing_enabled
# cat /debug/tracing/latency_trace
# echo 0 > tracing_enabled
# cat latency_trace
# tracer: wakeup
#
wakeup latency trace v1.1.5 on 2.6.26-rc8
@@ -1114,11 +1126,11 @@ 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
# echo function > /debug/tracing/current_tracer
# echo 1 > /debug/tracing/tracing_enabled
# echo function > current_tracer
# echo 1 > tracing_enabled
# 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
@@ -1155,7 +1167,7 @@ int trace_fd;
[...]
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);
@@ -1163,26 +1175,20 @@ 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
---------------------
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:
# cat /debug/tracing/set_ftrace_pid
# cat set_ftrace_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
# 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
@@ -1193,8 +1199,8 @@ 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
# 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
@@ -1216,6 +1222,51 @@ something like this simple program:
#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)
@@ -1226,12 +1277,12 @@ int main (int argc, char **argv)
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);
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);
@@ -1383,22 +1434,22 @@ want, depending on your needs.
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.
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.
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:
@@ -1427,8 +1478,8 @@ want, depending on your needs.
- 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:
@@ -1451,8 +1502,8 @@ want, depending on your needs.
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:
@@ -1549,7 +1600,7 @@ listed in:
available_filter_functions
# cat /debug/tracing/available_filter_functions
# cat available_filter_functions
put_prev_task_idle
kmem_cache_create
pick_next_task_rt
@@ -1561,12 +1612,12 @@ mutex_lock
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
# echo 0 > /debug/tracing/tracing_enabled
# cat /debug/tracing/trace
# echo 0 > tracing_enabled
# cat trace
# tracer: ftrace
#
# TASK-PID CPU# TIMESTAMP FUNCTION
@@ -1577,7 +1628,7 @@ If I am only interested in sys_nanosleep and hrtimer_interrupt:
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
@@ -1597,7 +1648,7 @@ 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.
# echo 'hrtimer_*' > /debug/tracing/set_ftrace_filter
# echo 'hrtimer_*' > set_ftrace_filter
Produces:
@@ -1618,7 +1669,7 @@ Produces:
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
@@ -1644,17 +1695,17 @@ To append to the filters, use '>>'
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.
# 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
# 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
@@ -1677,7 +1728,7 @@ hrtimer_init_sleeper
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:
@@ -1767,13 +1818,13 @@ 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.
# 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
# echo 1 > /debug/tracing/tracing_enabled
# echo 1 > tracing_enabled
# 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
@@ -1809,7 +1860,7 @@ 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.
# cat /debug/tracing/buffer_size_kb
# cat buffer_size_kb
1408 (units kilobytes)
Note, to modify this, you must have tracing completely disabled.
@@ -1817,18 +1868,18 @@ To do that, echo "nop" into the current_tracer. If the
current_tracer is not set to "nop", an EINVAL error will be
returned.
# 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.
# echo 1000000000000 > /debug/tracing/buffer_size_kb
# echo 1000000000000 > buffer_size_kb
-bash: echo: write error: Cannot allocate memory
# cat /debug/tracing/buffer_size_kb
# cat buffer_size_kb
85
-----------

26
Documentation/trace/mmiotrace.txt
View File

@@ -32,41 +32,41 @@ is no way to automatically detect if you are losing events due to CPUs racing.
Usage Quick Reference
---------------------
$ mount -t debugfs debugfs /debug
$ echo mmiotrace > /debug/tracing/current_tracer
$ cat /debug/tracing/trace_pipe > mydump.txt &
$ mount -t debugfs debugfs /sys/kernel/debug
$ echo mmiotrace > /sys/kernel/debug/tracing/current_tracer
$ cat /sys/kernel/debug/tracing/trace_pipe > mydump.txt &
Start X or whatever.
$ echo "X is up" > /debug/tracing/trace_marker
$ echo nop > /debug/tracing/current_tracer
$ echo "X is up" > /sys/kernel/debug/tracing/trace_marker
$ echo nop > /sys/kernel/debug/tracing/current_tracer
Check for lost events.
Usage
-----
Make sure debugfs is mounted to /debug. If not, (requires root privileges)
$ mount -t debugfs debugfs /debug
Make sure debugfs is mounted to /sys/kernel/debug. If not, (requires root privileges)
$ mount -t debugfs debugfs /sys/kernel/debug
Check that the driver you are about to trace is not loaded.
Activate mmiotrace (requires root privileges):
$ echo mmiotrace > /debug/tracing/current_tracer
$ echo mmiotrace > /sys/kernel/debug/tracing/current_tracer
Start storing the trace:
$ cat /debug/tracing/trace_pipe > mydump.txt &
$ cat /sys/kernel/debug/tracing/trace_pipe > mydump.txt &
The 'cat' process should stay running (sleeping) in the background.
Load the driver you want to trace and use it. Mmiotrace will only catch MMIO
accesses to areas that are ioremapped while mmiotrace is active.
During tracing you can place comments (markers) into the trace by
$ echo "X is up" > /debug/tracing/trace_marker
$ echo "X is up" > /sys/kernel/debug/tracing/trace_marker
This makes it easier to see which part of the (huge) trace corresponds to
which action. It is recommended to place descriptive markers about what you
do.
Shut down mmiotrace (requires root privileges):
$ echo nop > /debug/tracing/current_tracer
$ echo nop > /sys/kernel/debug/tracing/current_tracer
The 'cat' process exits. If it does not, kill it by issuing 'fg' command and
pressing ctrl+c.
@@ -78,10 +78,10 @@ to view your kernel log and look for "mmiotrace has lost events" warning. If
events were lost, the trace is incomplete. You should enlarge the buffers and
try again. Buffers are enlarged by first seeing how large the current buffers
are:
$ cat /debug/tracing/buffer_size_kb
$ cat /sys/kernel/debug/tracing/buffer_size_kb
gives you a number. Approximately double this number and write it back, for
instance:
$ echo 128000 > /debug/tracing/buffer_size_kb
$ echo 128000 > /sys/kernel/debug/tracing/buffer_size_kb
Then start again from the top.
If you are doing a trace for a driver project, e.g. Nouveau, you should also