From: Changbin Du <changbin.du@gmail.com>
To: rostedt@goodmis.org
Cc: mingo@redhat.com, corbet@lwn.net, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, Changbin Du <changbin.du@gmail.com>
Subject: [PATCH 5/5] trace/doc: Add latency tracer funcgraph example
Date: Tue, 1 Jan 2019 23:46:14 +0800 [thread overview]
Message-ID: <20190101154614.8887-6-changbin.du@gmail.com> (raw)
In-Reply-To: <20190101154614.8887-1-changbin.du@gmail.com>
This add an example about how to use funcgraph with latency tracers.
Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
Documentation/trace/ftrace.rst | 51 ++++++++++++++++++++++++++++++++++
1 file changed, 51 insertions(+)
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index 0131df7f5968..6ce2763a2a3e 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -1396,6 +1396,57 @@ enabling function tracing, we incur an added overhead. This
overhead may extend the latency times. But nevertheless, this
trace has provided some very helpful debugging information.
+If we prefer function graph output instead of function, we can set
+display-graph option::
+ with echo 1 > options/display-graph
+
+ # tracer: irqsoff
+ #
+ # irqsoff latency trace v1.1.5 on 4.20.0-rc6+
+ # --------------------------------------------------------------------
+ # latency: 3751 us, #274/274, CPU#0 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4)
+ # -----------------
+ # | task: bash-1507 (uid:0 nice:0 policy:0 rt_prio:0)
+ # -----------------
+ # => started at: free_debug_processing
+ # => ended at: return_to_handler
+ #
+ #
+ # _-----=> irqs-off
+ # / _----=> need-resched
+ # | / _---=> hardirq/softirq
+ # || / _--=> preempt-depth
+ # ||| /
+ # REL TIME CPU TASK/PID |||| DURATION FUNCTION CALLS
+ # | | | | |||| | | | | | |
+ 0 us | 0) bash-1507 | d... | 0.000 us | _raw_spin_lock_irqsave();
+ 0 us | 0) bash-1507 | d..1 | 0.378 us | do_raw_spin_trylock();
+ 1 us | 0) bash-1507 | d..2 | | set_track() {
+ 2 us | 0) bash-1507 | d..2 | | save_stack_trace() {
+ 2 us | 0) bash-1507 | d..2 | | __save_stack_trace() {
+ 3 us | 0) bash-1507 | d..2 | | __unwind_start() {
+ 3 us | 0) bash-1507 | d..2 | | get_stack_info() {
+ 3 us | 0) bash-1507 | d..2 | 0.351 us | in_task_stack();
+ 4 us | 0) bash-1507 | d..2 | 1.107 us | }
+ [...]
+ 3750 us | 0) bash-1507 | d..1 | 0.516 us | do_raw_spin_unlock();
+ 3750 us | 0) bash-1507 | d..1 | 0.000 us | _raw_spin_unlock_irqrestore();
+ 3764 us | 0) bash-1507 | d..1 | 0.000 us | tracer_hardirqs_on();
+ bash-1507 0d..1 3792us : <stack trace>
+ => free_debug_processing
+ => __slab_free
+ => kmem_cache_free
+ => vm_area_free
+ => remove_vma
+ => exit_mmap
+ => mmput
+ => flush_old_exec
+ => load_elf_binary
+ => search_binary_handler
+ => __do_execve_file.isra.32
+ => __x64_sys_execve
+ => do_syscall_64
+ => entry_SYSCALL_64_after_hwframe
preemptoff
----------
--
2.17.1
next prev parent reply other threads:[~2019-01-01 15:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-01 15:46 [PATCH 0/5] Improve the latency tracers Changbin Du
2019-01-01 15:46 ` [PATCH 1/5] function_graph: Support displaying relative timestamp Changbin Du
2019-01-01 15:46 ` [PATCH 2/5] sched/tracing: Show more info for funcgraph wakeup tracers Changbin Du
2019-01-01 15:46 ` [PATCH 3/5] sched/tracing: Put a margin between flags and duration for " Changbin Du
2019-01-01 15:46 ` [PATCH 4/5] sched/tracing: Show stacktrace " Changbin Du
2019-01-16 3:25 ` Steven Rostedt
2019-01-16 16:04 ` Changbin Du
2019-01-01 15:46 ` Changbin Du [this message]
2019-01-12 4:05 ` [PATCH 0/5] Improve the latency tracers Changbin Du
2019-01-14 15:00 ` Steven Rostedt
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