diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 8 | ||||
| -rw-r--r-- | Documentation/trace/timerlat-tracer.rst | 12 |
2 files changed, 14 insertions, 6 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index aef674df3afd..d1f313a5f4ad 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -366,6 +366,14 @@ of ftrace. Here is a list of some of the key files: for each function. The displayed address is the patch-site address and can differ from /proc/kallsyms address. + syscall_user_buf_size: + + Some system call trace events will record the data from a user + space address that one of the parameters point to. The amount of + data per event is limited. This file holds the max number of bytes + that will be recorded into the ring buffer to hold this data. + The max value is currently 165. + dyn_ftrace_total_info: This file is for debugging purposes. The number of functions that diff --git a/Documentation/trace/timerlat-tracer.rst b/Documentation/trace/timerlat-tracer.rst index 53a56823e903..68d429d454a5 100644 --- a/Documentation/trace/timerlat-tracer.rst +++ b/Documentation/trace/timerlat-tracer.rst @@ -43,12 +43,12 @@ It is possible to follow the trace by reading the trace file:: <...>-868 [001] .... 54.030347: #2 context thread timer_latency 4351 ns -The tracer creates a per-cpu kernel thread with real-time priority that -prints two lines at every activation. The first is the *timer latency* -observed at the *hardirq* context before the activation of the thread. -The second is the *timer latency* observed by the thread. The ACTIVATION -ID field serves to relate the *irq* execution to its respective *thread* -execution. +The tracer creates a per-cpu kernel thread with real-time priority +SCHED_FIFO:95 that prints two lines at every activation. The first is +the *timer latency* observed at the *hardirq* context before the activation +of the thread. The second is the *timer latency* observed by the thread. +The ACTIVATION ID field serves to relate the *irq* execution to its +respective *thread* execution. The *irq*/*thread* splitting is important to clarify in which context the unexpected high value is coming from. The *irq* context can be |