• Peter Zijlstra's avatar
    sched: Introduce the 'trace_sched_waking' tracepoint · fbd705a0
    Peter Zijlstra authored
    Mathieu reported that since 317f3941 ("sched: Move the second half
    of ttwu() to the remote cpu") trace_sched_wakeup() can happen out of
    context of the waker.
    
    This is a problem when you want to analyse wakeup paths because it is
    now very hard to correlate the wakeup event to whoever issued the
    wakeup.
    
    OTOH trace_sched_wakeup() is issued at the point where we set
    p->state = TASK_RUNNING, which is right were we hand the task off to
    the scheduler, so this is an important point when looking at
    scheduling behaviour, up to here its been the wakeup path everything
    hereafter is due to scheduler policy.
    
    To bridge this gap, introduce a second tracepoint: trace_sched_waking.
    It is guaranteed to be called in the waker context.
    Reported-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Francis Giraldeau <francis.giraldeau@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/20150609091336.GQ3644@twins.programming.kicks-ass.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    fbd705a0
trace_sched_wakeup.c 18.9 KB