NAME
perf-ftrace - simple wrapper for kernel's ftrace functionalitySYNOPSIS
perf ftrace {trace|latency} <command>
DESCRIPTION
The perf ftrace command provides a collection of subcommands which use kernel’s ftrace infrastructure.'perf ftrace trace' is a simple wrapper of the ftrace. It only supports single thread tracing currently and just reads trace_pipe in text and then write it to stdout.
'perf ftrace latency' calculates execution latency of a given function (optionally with BPF) and display it as a histogram.
COMMON OPTIONS
-p, --pid=Trace on existing process id (comma separated
list).
Trace on existing thread id (comma separated
list).
Force system-wide collection. Scripts run
without a <command> normally use -a by default, while scripts run with a
<command> normally don’t - this option allows the latter to be
run in system-wide mode.
Only trace for the list of CPUs provided.
Multiple CPUs can be provided as a comma separated list with no space like:
0,1. Ranges of CPUs are specified with -: 0-2. Default is to trace on all
online CPUs.
Increase the verbosity level.
OPTIONS FOR PERF FTRACE TRACE
-t, --tracer=Tracer to use when neither -G nor -F option is
not specified: function_graph or function.
List available functions to trace. It accepts
a pattern to only list interested functions.
Time (ms) to wait before starting tracing
after program start.
Set the size of per-cpu tracing buffer,
<size> is expected to be a number with appended unit character -
B/K/M/G.
Trace children processes spawned by our
target.
Select function tracer and set function filter
on the given function (or a glob pattern). Multiple functions can be given by
using this option more than once. The function argument also can be a glob
pattern. It will be passed to set_ftrace_filter in tracefs.
Select function tracer and do not trace
functions given by the argument. Like -T option, this can be used more than
once to specify multiple functions (or glob patterns). It will be passed to
set_ftrace_notrace in tracefs.
List of options allowed to set: call-graph -
Display kernel stack trace for function tracer. irq-info - Display irq context
info for function tracer.
Select function_graph tracer and set graph
filter on the given function (or a glob pattern). This is useful to trace for
functions executed from the given function. This can be used more than once to
specify multiple functions. It will be passed to set_graph_function in
tracefs.
Select function_graph tracer and set graph
notrace filter on the given function (or a glob pattern). Like -G option, this
is useful for the function_graph tracer only and disables tracing for function
executed from the given function. This can be used more than once to specify
multiple functions. It will be passed to set_graph_notrace in
tracefs.
List of options allowed to set: nosleep-time -
Measure on-CPU time only for function_graph tracer. noirqs - Ignore functions
that happen inside interrupt. verbose - Show process names, PIDs, timestamps,
etc. thresh=<n> - Setup trace duration threshold in microseconds.
depth=<n> - Set max depth for function graph tracer to follow.
OPTIONS FOR PERF FTRACE LATENCY
-T, --trace-funcs=Set the function name to get the histogram.
Unlike perf ftrace trace, it only allows single function to calculate the
histogram.
Use BPF to measure function latency instead of
using the ftrace (it uses function_graph tracer internally).
Use nano-second instead of micro-second as a
base unit of the histogram.
SEE ALSO
perf-record(1), perf-trace(1)2024-06-21 | perf |