• M
    sched: Add 'autogroup' scheduling feature: automated per session task groups · 5091faa4
    Mike Galbraith 提交于
    A recurring complaint from CFS users is that parallel kbuild has
    a negative impact on desktop interactivity.  This patch
    implements an idea from Linus, to automatically create task
    groups.  Currently, only per session autogroups are implemented,
    but the patch leaves the way open for enhancement.
    
    Implementation: each task's signal struct contains an inherited
    pointer to a refcounted autogroup struct containing a task group
    pointer, the default for all tasks pointing to the
    init_task_group.  When a task calls setsid(), a new task group
    is created, the process is moved into the new task group, and a
    reference to the preveious task group is dropped.  Child
    processes inherit this task group thereafter, and increase it's
    refcount.  When the last thread of a process exits, the
    process's reference is dropped, such that when the last process
    referencing an autogroup exits, the autogroup is destroyed.
    
    At runqueue selection time, IFF a task has no cgroup assignment,
    its current autogroup is used.
    
    Autogroup bandwidth is controllable via setting it's nice level
    through the proc filesystem:
    
      cat /proc/<pid>/autogroup
    
    Displays the task's group and the group's nice level.
    
      echo <nice level> > /proc/<pid>/autogroup
    
    Sets the task group's shares to the weight of nice <level> task.
    Setting nice level is rate limited for !admin users due to the
    abuse risk of task group locking.
    
    The feature is enabled from boot by default if
    CONFIG_SCHED_AUTOGROUP=y is selected, but can be disabled via
    the boot option noautogroup, and can also be turned on/off on
    the fly via:
    
      echo [01] > /proc/sys/kernel/sched_autogroup_enabled
    
    ... which will automatically move tasks to/from the root task group.
    Signed-off-by: NMike Galbraith <efault@gmx.de>
    Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
    Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Markus Trippelsdorf <markus@trippelsdorf.de>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Cc: Paul Turner <pjt@google.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    [ Removed the task_group_path() debug code, and fixed !EVENTFD build failure. ]
    Signed-off-by: NIngo Molnar <mingo@elte.hu>
    LKML-Reference: <1290281700.28711.9.camel@maggy.simson.net>
    Signed-off-by: NIngo Molnar <mingo@elte.hu>
    5091faa4
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