diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/coresight/coresight-perf.rst | 31 | ||||
| -rw-r--r-- | Documentation/trace/ftrace.rst | 13 | ||||
| -rw-r--r-- | Documentation/trace/tracepoints.rst | 17 |
3 files changed, 55 insertions, 6 deletions
diff --git a/Documentation/trace/coresight/coresight-perf.rst b/Documentation/trace/coresight/coresight-perf.rst index d087aae7d492..30be89320621 100644 --- a/Documentation/trace/coresight/coresight-perf.rst +++ b/Documentation/trace/coresight/coresight-perf.rst @@ -78,6 +78,37 @@ enabled like:: Please refer to the kernel configuration help for more information. +Fine-grained tracing with AUX pause and resume +---------------------------------------------- + +Arm CoreSight may generate a large amount of hardware trace data, which +will lead to overhead in recording and distract users when reviewing +profiling result. To mitigate the issue of excessive trace data, Perf +provides AUX pause and resume functionality for fine-grained tracing. + +The AUX pause and resume can be triggered by associated events. These +events can be ftrace tracepoints (including static and dynamic +tracepoints) or PMU events (e.g. CPU PMU cycle event). To create a perf +session with AUX pause / resume, three configuration terms are +introduced: + +- "aux-action=start-paused": it is specified for the cs_etm PMU event to + launch in a paused state. +- "aux-action=pause": an associated event is specified with this term + to pause AUX trace. +- "aux-action=resume": an associated event is specified with this term + to resume AUX trace. + +Example for triggering AUX pause and resume with ftrace tracepoints:: + + perf record -e cs_etm/aux-action=start-paused/k,syscalls:sys_enter_openat/aux-action=resume/,syscalls:sys_exit_openat/aux-action=pause/ ls + +Example for triggering AUX pause and resume with PMU event:: + + perf record -a -e cs_etm/aux-action=start-paused/k \ + -e cycles/aux-action=pause,period=10000000/ \ + -e cycles/aux-action=resume,period=1050000/ -- sleep 1 + Perf test - Verify kernel and userspace perf CoreSight work ----------------------------------------------------------- diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index c9e88bf65709..af66a05e18cc 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -1205,6 +1205,19 @@ Here are the available options: default instance. The only way the top level instance has this flag cleared, is by it being set in another instance. + copy_trace_marker + If there are applications that hard code writing into the top level + trace_marker file (/sys/kernel/tracing/trace_marker or trace_marker_raw), + and the tooling would like it to go into an instance, this option can + be used. Create an instance and set this option, and then all writes + into the top level trace_marker file will also be redirected into this + instance. + + Note, by default this option is set for the top level instance. If it + is disabled, then writes to the trace_marker or trace_marker_raw files + will not be written into the top level file. If no instance has this + option set, then a write will error with the errno of ENODEV. + annotate It is sometimes confusing when the CPU buffers are full and one CPU buffer had a lot of events recently, thus diff --git a/Documentation/trace/tracepoints.rst b/Documentation/trace/tracepoints.rst index decabcc77b56..b35c40e3abbe 100644 --- a/Documentation/trace/tracepoints.rst +++ b/Documentation/trace/tracepoints.rst @@ -71,7 +71,7 @@ In subsys/file.c (where the tracing statement must be added):: void somefct(void) { ... - trace_subsys_eventname(arg, task); + trace_subsys_eventname_tp(arg, task); ... } @@ -129,12 +129,12 @@ within an if statement with the following:: for (i = 0; i < count; i++) tot += calculate_nuggets(); - trace_foo_bar(tot); + trace_foo_bar_tp(tot); } -All trace_<tracepoint>() calls have a matching trace_<tracepoint>_enabled() +All trace_<tracepoint>_tp() calls have a matching trace_<tracepoint>_enabled() function defined that returns true if the tracepoint is enabled and -false otherwise. The trace_<tracepoint>() should always be within the +false otherwise. The trace_<tracepoint>_tp() should always be within the block of the if (trace_<tracepoint>_enabled()) to prevent races between the tracepoint being enabled and the check being seen. @@ -143,7 +143,10 @@ the static_key of the tracepoint to allow the if statement to be implemented with jump labels and avoid conditional branches. .. note:: The convenience macro TRACE_EVENT provides an alternative way to - define tracepoints. Check http://lwn.net/Articles/379903, + define tracepoints. Note, DECLARE_TRACE(foo) creates a function + "trace_foo_tp()" whereas TRACE_EVENT(foo) creates a function + "trace_foo()", and also exposes the tracepoint as a trace event in + /sys/kernel/tracing/events directory. Check http://lwn.net/Articles/379903, http://lwn.net/Articles/381064 and http://lwn.net/Articles/383362 for a series of articles with more details. @@ -159,7 +162,9 @@ In a C file:: void do_trace_foo_bar_wrapper(args) { - trace_foo_bar(args); + trace_foo_bar_tp(args); // for tracepoints created via DECLARE_TRACE + // or + trace_foo_bar(args); // for tracepoints created via TRACE_EVENT } In the header file:: |