diff options
author | Ingo Molnar <mingo@elte.hu> | 2008-07-13 08:50:13 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-07-13 08:50:13 +0200 |
commit | 54ef76f37bcccf8c16fbaaed13c3c40825195958 (patch) | |
tree | 59afdb95e68f2fbac2550aa42135921086649c38 | |
parent | 032f82786f9be4635acaa5f77feca175a4ac5fe1 (diff) | |
parent | 9df2fe986770bc4c76e8fe72c20b71268eec39a7 (diff) |
Merge branch 'linus' into sched/devel
136 files changed, 2315 insertions, 423 deletions
diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt new file mode 100644 index 000000000000..13e4bf054c38 --- /dev/null +++ b/Documentation/ftrace.txt @@ -0,0 +1,1353 @@ + ftrace - Function Tracer + ======================== + +Copyright 2008 Red Hat Inc. +Author: Steven Rostedt <srostedt@redhat.com> + + +Introduction +------------ + +Ftrace is an internal tracer designed to help out developers and +designers of systems to find what is going on inside the kernel. +It can be used for debugging or analyzing latencies and performance +issues that take place outside of user-space. + +Although ftrace is the function tracer, it also includes an +infrastructure that allows for other types of tracing. Some of the +tracers that are currently in ftrace is a tracer to trace +context switches, the time it takes for a high priority task to +run after it was woken up, the time interrupts are disabled, and +more. + + +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: + + # mkdir /debug + # mount -t debugfs nodev /debug + + +That's it! (assuming that you have ftrace configured into your kernel) + +After mounting the debugfs, you can see a directory called +"tracing". This directory contains the control and output files +of ftrace. Here is a list of some of the key files: + + + Note: all time values are in microseconds. + + current_tracer : This is used to set or display the current tracer + that is configured. + + available_tracers : This holds the different types of tracers that + has been compiled into the kernel. The tracers + listed here can be configured by echoing in their + name into current_tracer. + + tracing_enabled : This sets or displays whether the current_tracer + is activated and tracing or not. Echo 0 into this + file to disable the tracer or 1 (or non-zero) to + enable it. + + trace : This file holds the output of the trace in a human readable + format. + + latency_trace : This file shows the same trace but the information + is organized more to display possible latencies + in the system. + + 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 |