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    sched/core: Fix incorrect utilization accounting when switching to fair class · a399d233
    Vincent Guittot 提交于
    When a task switches to fair scheduling class, the period between now
    and the last update of its utilization is accounted as running time
    whatever happened during this period. This incorrect accounting applies
    to the task and also to the task group branch.
    
    When changing the property of a running task like its list of allowed
    CPUs or its scheduling class, we follow the sequence:
    
     - dequeue task
     - put task
     - change the property
     - set task as current task
     - enqueue task
    
    The end of the sequence doesn't follow the normal sequence (as per
    __schedule()) which is:
    
     - enqueue a task
     - then set the task as current task.
    
    This incorrectordering is the root cause of incorrect utilization accounting.
    Update the sequence to follow the right one:
    
     - dequeue task
     - put task
     - change the property
     - enqueue task
     - set task as current task
    Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
    Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Morten.Rasmussen@arm.com
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: bsegall@google.com
    Cc: dietmar.eggemann@arm.com
    Cc: linaro-kernel@lists.linaro.org
    Cc: pjt@google.com
    Cc: yuyang.du@intel.com
    Link: http://lkml.kernel.org/r/1473666472-13749-8-git-send-email-vincent.guittot@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
    a399d233
core.c 216.3 KB