• Frederic Weisbecker's avatar
    trace: better manage the context info for events · c4a8e8be
    Frederic Weisbecker authored
    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: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>