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authorIngo Molnar <mingo@elte.hu>2011-02-17 08:11:15 -0500
committerIngo Molnar <mingo@elte.hu>2011-02-17 08:11:15 -0500
commit5beda5f6e4e4523e8dbe596bf163a01b45776808 (patch)
tree61d1551430687b712325cdfec81b7800aa759076 /Documentation/trace
parentba3dd36c6775264ee6e7354ba1aabcd6e86d7298 (diff)
parent6752ab4a9c30d5411b2dfdb251a3f1cb18aae487 (diff)
Merge branch 'tip/perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/core
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/ftrace-design.txt7
-rw-r--r--Documentation/trace/ftrace.txt148
2 files changed, 26 insertions, 129 deletions
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index dc52bd442c92..79fcafc7fd64 100644
--- a/Documentation/trace/ftrace-design.txt
+++ b/Documentation/trace/ftrace-design.txt
@@ -247,6 +247,13 @@ You need very few things to get the syscalls tracing in an arch.
247- Support the TIF_SYSCALL_TRACEPOINT thread flags. 247- Support the TIF_SYSCALL_TRACEPOINT thread flags.
248- Put the trace_sys_enter() and trace_sys_exit() tracepoints calls from ptrace 248- Put the trace_sys_enter() and trace_sys_exit() tracepoints calls from ptrace
249 in the ptrace syscalls tracing path. 249 in the ptrace syscalls tracing path.
250- If the system call table on this arch is more complicated than a simple array
251 of addresses of the system calls, implement an arch_syscall_addr to return
252 the address of a given system call.
253- If the symbol names of the system calls do not match the function names on
254 this arch, define ARCH_HAS_SYSCALL_MATCH_SYM_NAME in asm/ftrace.h and
255 implement arch_syscall_match_sym_name with the appropriate logic to return
256 true if the function name corresponds with the symbol name.
250- Tag this arch as HAVE_SYSCALL_TRACEPOINTS. 257- Tag this arch as HAVE_SYSCALL_TRACEPOINTS.
251 258
252 259
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 557c1edeccaf..67f1cc473257 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -80,11 +80,11 @@ of ftrace. Here is a list of some of the key files:
80 tracers listed here can be configured by 80 tracers listed here can be configured by
81 echoing their name into current_tracer. 81 echoing their name into current_tracer.
82 82
83 tracing_enabled: 83 tracing_on:
84 84
85 This sets or displays whether the current_tracer 85 This sets or displays whether writing to the trace
86 is activated and tracing or not. Echo 0 into this 86 ring buffer is enabled. Echo 0 into this file to disable
87 file to disable the tracer or 1 to enable it. 87 the tracer or 1 to enable it.
88 88
89 trace: 89 trace:
90 90
@@ -202,10 +202,6 @@ Here is the list of current tracers that may be configured.
202 to draw a graph of function calls similar to C code 202 to draw a graph of function calls similar to C code
203 source. 203 source.
204 204
205 "sched_switch"
206
207 Traces the context switches and wakeups between tasks.
208
209 "irqsoff" 205 "irqsoff"
210 206
211 Traces the areas that disable interrupts and saves 207 Traces the areas that disable interrupts and saves
@@ -273,39 +269,6 @@ format, the function name that was traced "path_put" and the
273parent function that called this function "path_walk". The 269parent function that called this function "path_walk". The
274timestamp is the time at which the function was entered. 270timestamp is the time at which the function was entered.
275 271
276The sched_switch tracer also includes tracing of task wakeups
277and context switches.
278
279 ksoftirqd/1-7 [01] 1453.070013: 7:115:R + 2916:115:S
280 ksoftirqd/1-7 [01] 1453.070013: 7:115:R + 10:115:S
281 ksoftirqd/1-7 [01] 1453.070013: 7:115:R ==> 10:115:R
282 events/1-10 [01] 1453.070013: 10:115:S ==> 2916:115:R
283 kondemand/1-2916 [01] 1453.070013: 2916:115:S ==> 7:115:R
284 ksoftirqd/1-7 [01] 1453.070013: 7:115:S ==> 0:140:R
285
286Wake ups are represented by a "+" and the context switches are
287shown as "==>". The format is:
288
289 Context switches:
290
291 Previous task Next Task
292
293 <pid>:<prio>:<state> ==> <pid>:<prio>:<state>
294
295 Wake ups:
296
297 Current task Task waking up
298
299 <pid>:<prio>:<state> + <pid>:<prio>:<state>
300
301The prio is the internal kernel priority, which is the inverse
302of the priority that is usually displayed by user-space tools.
303Zero represents the highest priority (99). Prio 100 starts the
304"nice" priorities with 100 being equal to nice -20 and 139 being
305nice 19. The prio "140" is reserved for the idle task which is
306the lowest priority thread (pid 0).
307
308
309Latency trace format 272Latency trace format
310-------------------- 273--------------------
311 274
@@ -491,79 +454,6 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
491 latencies, as described in "Latency 454 latencies, as described in "Latency
492 trace format". 455 trace format".
493 456
494sched_switch
495------------
496
497This tracer simply records schedule switches. Here is an example
498of how to use it.
499
500 # echo sched_switch > current_tracer
501 # echo 1 > tracing_enabled
502 # sleep 1
503 # echo 0 > tracing_enabled
504 # cat trace
505
506# tracer: sched_switch
507#
508# TASK-PID CPU# TIMESTAMP FUNCTION
509# | | | | |
510 bash-3997 [01] 240.132281: 3997:120:R + 4055:120:R
511 bash-3997 [01] 240.132284: 3997:120:R ==> 4055:120:R
512 sleep-4055 [01] 240.132371: 4055:120:S ==> 3997:120:R
513 bash-3997 [01] 240.132454: 3997:120:R + 4055:120:S
514 bash-3997 [01] 240.132457: 3997:120:R ==> 4055:120:R
515 sleep-4055 [01] 240.132460: 4055:120:D ==> 3997:120:R
516 bash-3997 [01] 240.132463: 3997:120:R + 4055:120:D
517 bash-3997 [01] 240.132465: 3997:120:R ==> 4055:120:R
518 <idle>-0 [00] 240.132589: 0:140:R + 4:115:S
519 <idle>-0 [00] 240.132591: 0:140:R ==> 4:115:R
520 ksoftirqd/0-4 [00] 240.132595: 4:115:S ==> 0:140:R
521 <idle>-0 [00] 240.132598: 0:140:R + 4:115:S
522 <idle>-0 [00] 240.132599: 0:140:R ==> 4:115:R
523 ksoftirqd/0-4 [00] 240.132603: 4:115:S ==> 0:140:R
524 sleep-4055 [01] 240.133058: 4055:120:S ==> 3997:120:R
525 [...]
526
527
528As we have discussed previously about this format, the header
529shows the name of the trace and points to the options. The
530"FUNCTION" is a misnomer since here it represents the wake ups
531and context switches.
532
533The sched_switch file only lists the wake ups (represented with
534'+') and context switches ('==>') with the previous task or
535current task first followed by the next task or task waking up.
536The format for both of these is PID:KERNEL-PRIO:TASK-STATE.
537Remember that the KERNEL-PRIO is the inverse of the actual
538priority with zero (0) being the highest priority and the nice
539values starting at 100 (nice -20). Below is a quick chart to map
540the kernel priority to user land priorities.
541
542 Kernel Space User Space
543 ===============================================================
544 0(high) to 98(low) user RT priority 99(high) to 1(low)
545 with SCHED_RR or SCHED_FIFO
546 ---------------------------------------------------------------
547 99 sched_priority is not used in scheduling
548 decisions(it must be specified as 0)
549 ---------------------------------------------------------------
550 100(high) to 139(low) user nice -20(high) to 19(low)
551 ---------------------------------------------------------------
552 140 idle task priority
553 ---------------------------------------------------------------
554
555The task states are:
556
557 R - running : wants to run, may not actually be running
558 S - sleep : process is waiting to be woken up (handles signals)
559 D - disk sleep (uninterruptible sleep) : process must be woken up
560 (ignores signals)
561 T - stopped : process suspended
562 t - traced : process is being traced (with something like gdb)
563 Z - zombie : process waiting to be cleaned up
564 X - unknown
565
566
567ftrace_enabled 457ftrace_enabled
568-------------- 458--------------
569 459
@@ -607,10 +497,10 @@ an example:
607 # echo irqsoff > current_tracer 497 # echo irqsoff > current_tracer
608 # echo latency-format > trace_options 498 # echo latency-format > trace_options
609 # echo 0 > tracing_max_latency 499 # echo 0 > tracing_max_latency
610 # echo 1 > tracing_enabled 500 # echo 1 > tracing_on