• Steven Rostedt's avatar
    workqueue: It is likely that WORKER_NOT_RUNNING is true · 2d64672e
    Steven Rostedt authored
    Running the annotate branch profiler on three boxes, including my
    main box that runs firefox, evolution, xchat, and is part of the distcc farm,
    showed this with the likelys in the workqueue code:
    
     correct incorrect  %        Function                  File              Line
     ------- ---------  -        --------                  ----              ----
          96   996253  99 wq_worker_sleeping             workqueue.c          703
          96   996247  99 wq_worker_waking_up            workqueue.c          677
    
    The likely()s in this case were assuming that WORKER_NOT_RUNNING will
    most likely be false. But this is not the case. The reason is
    (and shown by adding trace_printks and testing it) that most of the time
    WORKER_PREP is set.
    
    In worker_thread() we have:
    
    	worker_clr_flags(worker, WORKER_PREP);
    
    	[ do work stuff ]
    
    	worker_set_flags(worker, WORKER_PREP, false);
    
    (that 'false' means not to wake up an idle worker)
    
    The wq_worker_sleeping() is called from schedule when a worker thread
    is putting itself to sleep. Which happens most of the time outside
    of that [ do work stuff ].
    
    The wq_worker_waking_up is called by the wakeup worker code, which
    is also callod outside that [ do work stuff ].
    
    Thus, the likely and unlikely used by those two functions are actually
    backwards.
    
    Remove the annotation and let gcc figure it out.
    Acked-by: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    2d64672e
workqueue.c 100 KB