linux/Documentation/trace
Steven Rostedt 94d529a325 ftrace: Document that multiple function_graph tracing may have different times
The function graph tracer now calculates the calltime internally and for
each instance. If there are two instances that are running function graph
tracer and are tracing the same functions, the timings of the length of
those functions may be slightly different:

 # trace-cmd record -B foo -p function_graph -B bar -p function_graph sleep 5
 # trace-cmd report
[..]
bar:            sleep-981   [000] ...1.  1101.109027: funcgraph_entry:        0.764 us   |          mutex_unlock(); (ret=0xffff8abcc256c300)
foo:            sleep-981   [000] ...1.  1101.109028: funcgraph_entry:        0.748 us   |          mutex_unlock(); (ret=0xffff8abcc256c300)
bar:            sleep-981   [000] .....  1101.109029: funcgraph_exit:         2.456 us   |        } (ret=0xffff8abcc256c300)
foo:            sleep-981   [000] .....  1101.109029: funcgraph_exit:         2.403 us   |        } (ret=0xffff8abcc256c300)
bar:            sleep-981   [000] d..1.  1101.109031: funcgraph_entry:        0.844 us   |  fpregs_assert_state_consistent(); (ret=0x0)
foo:            sleep-981   [000] d..1.  1101.109032: funcgraph_entry:        0.803 us   |  fpregs_assert_state_consistent(); (ret=0x0)

Link: https://lore.kernel.org/all/20250114101806.b2778cb01f34f5be9d23ad98@kernel.org/

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/20250114101202.02e7bc68@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2025-01-14 10:45:24 -05:00
..
coresight Documentation: coresight: Add cc_threshold tunable 2023-11-16 11:35:09 +00:00
postprocess
rv
boottime-trace.rst
debugging.rst tracing/Documentation: Start a document on how to debug with tracing 2024-08-26 13:54:08 -04:00
events-kmem.rst
events-msr.rst
events-nmi.rst
events-power.rst
events.rst
fprobe.rst
fprobetrace.rst Documentation: tracing: Fix spelling mistakes 2024-05-07 08:00:25 -06:00
ftrace-design.rst function_graph: Everyone uses HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, remove it 2024-06-11 11:18:24 -04:00
ftrace-uses.rst Documentation/trace: Fixed typos in the ftrace FLAGS section 2024-01-03 14:15:53 -07:00
ftrace.rst ftrace: Document that multiple function_graph tracing may have different times 2025-01-14 10:45:24 -05:00
function-graph-fold.vim
hisi-ptt.rst Documentation: ABI + trace: hisi_ptt: update paths to bus/event_source 2024-05-02 11:36:11 +01:00
histogram-design.rst
histogram.rst tracing: doc: Fix typo in ftrace histogram 2024-10-07 11:50:54 -06:00
hwlat_detector.rst
index.rst docs: fix WARNING document not included in any toctree 2024-10-07 11:50:54 -06:00
intel_th.rst
kprobes.rst docs, kprobes: Add riscv as supported architecture 2024-05-02 10:05:25 -06:00
kprobetrace.rst Probes updates for v6.10: 2024-05-17 18:29:30 -07:00
mmiotrace.rst
osnoise-tracer.rst rtla/osnoise: set the default threshold to 1us 2024-07-01 18:54:31 -04:00
ring-buffer-design.rst
ring-buffer-map.rst Documentation: tracing: Add ring-buffer mapping 2024-05-13 18:09:56 -04:00
stm.rst
sys-t.rst
timerlat-tracer.rst
tracepoint-analysis.rst
tracepoints.rst trace doc: Minor grammatical correction 2024-04-02 10:07:51 -06:00
uprobetracer.rst
user_events.rst tracing/user_events: Document multi-format flag 2024-03-18 10:13:16 -04:00