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trace: better manage the context info for events

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Impact: make trace_event more convenient for tracers

All tracers (for the moment) that use the struct trace_event want to
have the context info printed before their own output: the pid/cmdline,
cpu, and timestamp.

But some other tracers that want to implement their trace_event
callbacks will not necessary need these information or they may want to
format them as they want.

This patch adds a new default-enabled trace option:
TRACE_ITER_CONTEXT_INFO When disabled through:

echo nocontext-info > /debugfs/tracing/trace_options

The pid, cpu and timestamps headers will not be printed.

IE with the sched_switch tracer with context-info (default):

     bash-2935 [001] 100.356561: 2935:120:S ==> [001]  0:140:R <idle>
   <idle>-0    [000] 100.412804:    0:140:R   + [000] 11:115:S events/0
   <idle>-0    [000] 100.412816:    0:140:R ==> [000] 11:115:R events/0
 events/0-11   [000] 100.412829:   11:115:S ==> [000]  0:140:R <idle>

Without context-info:

 2935:120:S ==> [001]  0:140:R <idle>
    0:140:R   + [000] 11:115:S events/0
    0:140:R ==> [000] 11:115:R events/0
   11:115:S ==> [000]  0:140:R <idle>

A tracer can disable it at runtime by clearing the bit
TRACE_ITER_CONTEXT_INFO in trace_flags.

The print routines were renamed to trace_print_context and
trace_print_lat_context, so that they can be used by tracers if they
want to use them for one of the trace_event callbacks.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2009-02-02 20:29:21 -02:00 • committed by Ingo Molnar
parent dc573f9b20
commit c4a8e8be2d
4 changed files with 151 additions and 115 deletions
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3
kernel/trace/trace_output.h
View file

@ -33,6 +33,9 @@ int seq_print_userip_objs(const struct userstack_entry *entry,
int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm,
unsigned long ip, unsigned long sym_flags);
int trace_print_context(struct trace_iterator *iter);
int trace_print_lat_context(struct trace_iterator *iter);
struct trace_event *ftrace_find_event(int type);
int register_ftrace_event(struct trace_event *event);
int unregister_ftrace_event(struct trace_event *event);