diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace-uses.rst | 4 | ||||
| -rw-r--r-- | Documentation/trace/ftrace.rst | 17 |
2 files changed, 18 insertions, 3 deletions
diff --git a/Documentation/trace/ftrace-uses.rst b/Documentation/trace/ftrace-uses.rst index f7d98ae5b885..e198854ace79 100644 --- a/Documentation/trace/ftrace-uses.rst +++ b/Documentation/trace/ftrace-uses.rst @@ -182,7 +182,7 @@ FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED FTRACE_OPS_FL_RECURSION By default, it is expected that the callback can handle recursion. - But if the callback is not that worried about overehead, then + But if the callback is not that worried about overhead, then setting this bit will add the recursion protection around the callback by calling a helper function that will do the recursion protection and only call the callback if it did not recurse. @@ -190,7 +190,7 @@ FTRACE_OPS_FL_RECURSION Note, if this flag is not set, and recursion does occur, it could cause the system to crash, and possibly reboot via a triple fault. - Not, if this flag is set, then the callback will always be called + Note, if this flag is set, then the callback will always be called with preemption disabled. If it is not set, then it is possible (but not guaranteed) that the callback will be called in preemptable context. diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 23572f6697c0..16122a8895ba 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -180,6 +180,21 @@ of ftrace. Here is a list of some of the key files: Only active when the file contains a number greater than 0. (in microseconds) + buffer_percent: + + This is the watermark for how much the ring buffer needs to be filled + before a waiter is woken up. That is, if an application calls a + blocking read syscall on one of the per_cpu trace_pipe_raw files, it + will block until the given amount of data specified by buffer_percent + is in the ring buffer before it wakes the reader up. This also + controls how the splice system calls are blocked on this file:: + + 0 - means to wake up as soon as there is any data in the ring buffer. + 50 - means to wake up when roughly half of the ring buffer sub-buffers + are full. + 100 - means to block until the ring buffer is totally full and is + about to start overwriting the older data. + buffer_size_kb: This sets or displays the number of kilobytes each CPU @@ -2574,7 +2589,7 @@ want, depending on your needs. - The cpu number on which the function executed is default enabled. It is sometimes better to only trace one cpu (see - tracing_cpu_mask file) or you might sometimes see unordered + tracing_cpumask file) or you might sometimes see unordered function calls while cpu tracing switch. - hide: echo nofuncgraph-cpu > trace_options |