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
2024-09-01 20:43:24 -07:00
2022-09-28 09:02:20 +02:00
2025-01-12 14:37:56 -08:00
2024-03-18 03:36:32 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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