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| author |   Changbin Du <changbin.du@gmail.com> | 2019-01-01 23:46:14 +0800 |
|---|---|---|
| committer |   Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-02-06 11:56:19 -0500 |
| commit | 88d380eb0668b7fe76834c1febef4165508098b6 (patch) | |
| tree | 33874077c4483cbb7bd676682a09c654f1db81dd /Documentation/trace | |
| parent | tracing: Put a margin between flags and duration for wakeup tracers (diff) | |
| download | linux-dev-88d380eb0668b7fe76834c1febef4165508098b6.tar.xz linux-dev-88d380eb0668b7fe76834c1febef4165508098b6.zip | |
tracing/doc: Add latency tracer funcgraph example
This add an example about how to use funcgraph with latency tracers.
Link: http://lkml.kernel.org/r/20190101154614.8887-6-changbin.du@gmail.com
Signed-off-by: Changbin Du <changbin.du@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 51 |
1 files changed, 51 insertions, 0 deletions
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 ---------- |