SYNOPSIS

#include <tracefs.h>

enum tracefs_option_id {
        TRACEFS_OPTION_INVALID,
        TRACEFS_OPTION_ANNOTATE,
        TRACEFS_OPTION_BIN,
        TRACEFS_OPTION_BLK_CGNAME,
        TRACEFS_OPTION_BLK_CGROUP,
        TRACEFS_OPTION_BLK_CLASSIC,
        TRACEFS_OPTION_BLOCK,
        TRACEFS_OPTION_CONTEXT_INFO,
        TRACEFS_OPTION_DISABLE_ON_FREE,
        TRACEFS_OPTION_DISPLAY_GRAPH,
        TRACEFS_OPTION_EVENT_FORK,
        TRACEFS_OPTION_FGRAPH_ABSTIME,
        TRACEFS_OPTION_FGRAPH_CPU,
        TRACEFS_OPTION_FGRAPH_DURATION,
        TRACEFS_OPTION_FGRAPH_IRQS,
        TRACEFS_OPTION_FGRAPH_OVERHEAD,
        TRACEFS_OPTION_FGRAPH_OVERRUN,
        TRACEFS_OPTION_FGRAPH_PROC,
        TRACEFS_OPTION_FGRAPH_TAIL,
        TRACEFS_OPTION_FUNC_STACKTRACE,
        TRACEFS_OPTION_FUNCTION_FORK,
        TRACEFS_OPTION_FUNCTION_TRACE,
        TRACEFS_OPTION_GRAPH_TIME,
        TRACEFS_OPTION_HEX,
        TRACEFS_OPTION_IRQ_INFO,
        TRACEFS_OPTION_LATENCY_FORMAT,
        TRACEFS_OPTION_MARKERS,
        TRACEFS_OPTION_OVERWRITE,
        TRACEFS_OPTION_PAUSE_ON_TRACE,
        TRACEFS_OPTION_PRINTK_MSG_ONLY,
        TRACEFS_OPTION_PRINT_PARENT,
        TRACEFS_OPTION_RAW,
        TRACEFS_OPTION_RECORD_CMD,
        TRACEFS_OPTION_RECORD_TGID,
        TRACEFS_OPTION_SLEEP_TIME,
        TRACEFS_OPTION_STACKTRACE,
        TRACEFS_OPTION_SYM_ADDR,
        TRACEFS_OPTION_SYM_OFFSET,
        TRACEFS_OPTION_SYM_USEROBJ,
        TRACEFS_OPTION_TRACE_PRINTK,
        TRACEFS_OPTION_USERSTACKTRACE,
        TRACEFS_OPTION_VERBOSE,
};

DESCRIPTION

This enum contains all ftrace options, that can be manipulated using tracefs library. More detailed information about each option is available in Documentation/trace/ftrace.rst from the Linux kernel tree, in the trace_options section. Note that some ftrace options cannot be manipulated by this library, as they are intended for internal, debug purposes. These options control the tracers or the trace output. All options have two states - on and off, the default state is different for each of them.

Common options for all tracers:
        TRACEFS_OPTION_INVALID Not a valid ftrace option, used by the API to indicate an error.
        TRACEFS_OPTION_ANNOTATE Display when a new CPU buffer started.
        TRACEFS_OPTION_BIN Display the formats in raw binary.
        TRACEFS_OPTION_CONTEXT_INFO Show only the event data. Hides the comm, PID, timestamp, CPU, and other useful data.
        TRACEFS_OPTION_BLOCK When set, reading trace_pipe will not block when polled.
        TRACEFS_OPTION_DISABLE_ON_FREE When the free_buffer is closed, tracing will stop.
        TRACEFS_OPTION_DISPLAY_GRAPH When set, the latency tracers will use function graph tracing instead of function tracing.
        TRACEFS_OPTION_EVENT_FORK When set, tasks with PIDs listed in set_event_pid will have the PIDs of their children added to set_event_pid when those tasks fork.
        TRACEFS_OPTION_FUNCTION_FORK When set, tasks with PIDs listed in set_ftrace_pid will have the PIDs of their children added to set_ftrace_pid when those tasks fork.
        TRACEFS_OPTION_FUNCTION_TRACE When enabled, the latency tracers will trace functions.
        TRACEFS_OPTION_HEX Display numbers in a hexadecimal format.
        TRACEFS_OPTION_IRQ_INFO Display the interrupt, preempt count, need resched data.
        TRACEFS_OPTION_LATENCY_FORMAT Display additional information about the latency.
        TRACEFS_OPTION_MARKERS When set, the trace_marker is enabled - writable (only by root).
        TRACEFS_OPTION_OVERWRITE Controls what happens when the trace buffer is full. If set, the oldest events are discarded and overwritten. If disabled, then the newest events are discarded.
        TRACEFS_OPTION_PAUSE_ON_TRACE When set, opening the trace file for read, will pause writing to the ring buffer. When the file is closed, tracing will be enabled again.
        TRACEFS_OPTION_PRINTK_MSG_ONLY When set, trace_printk()s will only show the format and not their parameters.
        TRACEFS_OPTION_PRINT_PARENT On function traces, display the calling (parent) function as well as the function being traced.
        TRACEFS_OPTION_RAW Display raw numbers.
        TRACEFS_OPTION_RECORD_CMD Save a mapping with a pid and corresponding command.
        TRACEFS_OPTION_RECORD_TGID Save a mapping with a pid and corresponding Thread Group IDs.
        TRACEFS_OPTION_STACKTRACE Record a stack trace after any trace event.
        TRACEFS_OPTION_SYM_ADDR Display the function address as well as the function name.
        TRACEFS_OPTION_SYM_OFFSET Display not only the function name, but also the offset in the function.
        TRACEFS_OPTION_SYM_USEROBJ When TRACEFS_OPTION_USERSTACKTRACE is set, look up which object the address belongs to, and print the object and a relative address.
        TRACEFS_OPTION_TRACE_PRINTK Disable trace_printk() from writing into the buffer.
        TRACEFS_OPTION_USERSTACKTRACE Records a stack trace of the current user space thread after each trace event.
        TRACEFS_OPTION_VERBOSE When TRACEFS_OPTION_LATENCY_FORMAT is enabled, print more detailed information.

Options, specific to function tracer:
        TRACEFS_OPTION_FUNC_STACKTRACE Record a stack trace after every function.

Options, specific to function_graph tracer:
        TRACEFS_OPTION_FGRAPH_ABSTIME Display the timestamp at each line.
        TRACEFS_OPTION_FGRAPH_CPU Display the CPU number of the CPU where the trace occurred.
        TRACEFS_OPTION_FGRAPH_DURATION Display the duration of the amount of time at the end of each function, in microseconds.
        TRACEFS_OPTION_FGRAPH_IRQS Trace functions that happen inside an interrupt.
        TRACEFS_OPTION_FGRAPH_OVERHEAD Display a marker if a function takes longer than a certain amount of time.
        TRACEFS_OPTION_FGRAPH_OVERRUN Display "overrun" of the call graph, in the case of functions missed due to big callstack.
        TRACEFS_OPTION_FGRAPH_PROC Display the command of each process at every line.
        TRACEFS_OPTION_FGRAPH_TAIL Display the function name on its return.
        TRACEFS_OPTION_SLEEP_TIME Account time the task has been scheduled out as part of the function call.
        TRACEFS_OPTION_GRAPH_TIME Display the time to call nested functions, if function profiler is enabled.

Options, specific to blk tracer:
        TRACEFS_OPTION_BLK_CGNAME
        TRACEFS_OPTION_BLK_CGROUP
        TRACEFS_OPTION_BLK_CLASSIC Display a more minimalistic output.

FILES

tracefs.h
        Header file to include in order to have access to the library APIs.
-ltracefs
        Linker switch to add when building a program that uses the library.

SEE ALSO

libtracefs(3), libtraceevent(3), trace-cmd(1), Documentation/trace/ftrace.rst from the Linux kernel tree.

AUTHOR

Steven Rostedt <rostedt@goodmis.org>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com>

REPORTING BUGS

LICENSE

libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES

COPYING

Copyright (C) 2021 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).