5091faa449
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: Mike Galbraith <efault@gmx.de> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Peter 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: Ingo Molnar <mingo@elte.hu> LKML-Reference: <1290281700.28711.9.camel@maggy.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
33 lines
712 B
C
33 lines
712 B
C
#ifdef CONFIG_SCHED_AUTOGROUP
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struct autogroup {
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struct kref kref;
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struct task_group *tg;
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struct rw_semaphore lock;
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unsigned long id;
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int nice;
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};
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static inline struct task_group *
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autogroup_task_group(struct task_struct *p, struct task_group *tg);
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#else /* !CONFIG_SCHED_AUTOGROUP */
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static inline void autogroup_init(struct task_struct *init_task) { }
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static inline void autogroup_free(struct task_group *tg) { }
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static inline struct task_group *
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autogroup_task_group(struct task_struct *p, struct task_group *tg)
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{
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return tg;
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}
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#ifdef CONFIG_SCHED_DEBUG
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static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
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{
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return 0;
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}
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#endif
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#endif /* CONFIG_SCHED_AUTOGROUP */
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