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authorIngo Molnar <mingo@elte.hu>2009-09-06 06:27:40 +0200
committerIngo Molnar <mingo@elte.hu>2009-09-06 06:27:40 +0200
commitd28daf923ac5e4a0d7cecebae56f3e339189366b (patch)
tree8c8dff978e186bcd91ad60caa484480d3ed4ac11
parented011b22ce567eabefa9ea571d3721c10ecd0553 (diff)
parent4a88d44ab17da5f8a238050d1b43dfd2e204bc2f (diff)
Merge branch 'tracing/core' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing into tracing/core
-rw-r--r--Documentation/trace/ftrace.txt68
-rw-r--r--kernel/trace/trace_events_filter.c11
2 files changed, 42 insertions, 37 deletions
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index a39b3c749de5..355d0f1f8c50 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -85,26 +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).
- 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.
- 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:
@@ -117,10 +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
- 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:
@@ -210,7 +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
- trace via the latency_trace file.
+ trace with the latency-format option enabled.
"preemptoff"
@@ -307,8 +300,8 @@ the lowest priority thread (pid 0).
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
@@ -380,9 +373,10 @@ explains which is which.
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.
@@ -440,7 +434,8 @@ Here are the available options:
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)
@@ -472,7 +467,7 @@ Here are the available options:
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]
@@ -481,6 +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.
+ 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
------------
@@ -596,12 +596,13 @@ To reset the maximum, echo 0 into tracing_max_latency. Here is
an example:
# echo irqsoff > current_tracer
+ # echo latency-format > trace_options
# echo 0 > tracing_max_latency
# echo 1 > tracing_enabled
# ls -ltr
[...]
# echo 0 > tracing_enabled
- # cat latency_trace
+ # cat trace
# tracer: irqsoff
#
irqsoff latency trace v1.1.5 on 2.6.26
@@ -703,12 +704,13 @@ which preemption was disabled. The control of preemptoff tracer
is much like the irqsoff tracer.
# echo preemptoff > current_tracer
+ # echo latency-format > trace_options
# echo 0 > tracing_max_latency
# echo 1 > tracing_enabled
# ls -ltr
[...]
# echo 0 > tracing_enabled
- # cat latency_trace
+ # cat trace
# tracer: preemptoff
#
preemptoff latency trace v1.1.5 on 2.6.26-rc8
@@ -850,12 +852,13 @@ Again, using this trace is much like the irqsoff and preemptoff
tracers.
# echo preemptirqsoff > current_tracer
+ # echo latency-format > trace_options
# echo 0 > tracing_max_latency
# echo 1 > tracing_enabled
# ls -ltr
[...]
# echo 0 > tracing_enabled
- # cat latency_trace
+ # cat trace
# tracer: preemptirqsoff
#
preemptirqsoff latency trace v1.1.5 on 2.6.26-rc8
@@ -1012,11 +1015,12 @@ Instead of performing an 'ls', we will run 'sleep 1' under
'chrt' which changes the priority of the task.
# echo wakeup > current_tracer
+ # echo latency-format > trace_options
# echo 0 > tracing_max_latency
# echo 1 > tracing_enabled
# chrt -f 5 sleep 1
# echo 0 > tracing_enabled
- # cat latency_trace
+ # cat trace
# tracer: wakeup
#
wakeup latency trace v1.1.5 on 2.6.26-rc8
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index c6b2edfb7fe9..93660fbbf629 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -409,6 +409,9 @@ static int init_preds(struct ftrace_event_call *call)
struct filter_pred *pred;
int i;
+ if (call->filter)
+ return 0;
+
filter = call->filter = kzalloc(sizeof(*filter), GFP_KERNEL);
if (!call->filter)
return -ENOMEM;
@@ -447,11 +450,9 @@ static int init_subsystem_preds(struct event_subsystem *system)
if (strcmp(call->system, system->name) != 0)
continue;
- if (!call->filter) {
- err = init_preds(call);
- if (err)
- return err;
- }
+ err = init_preds(call);
+ if (err)
+ return err;
}
return 0;

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