Messages in this thread | | | Subject | [PATCH 0/5] sched: Add on_rq states and remove several double rq locks | From | Kirill Tkhai <> | Date | Tue, 22 Jul 2014 15:30:01 +0400 |
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This series aims to get rid of some places where locks of two RQs are held at the same time.
Patch [1/5] is a preparation/cleanup. It replaces old (.on_rq == 1) with new (.on_rq == ONRQ_QUEUED) everywhere. No functional changes.
Patch [2/5] is main in the series. It introduces new state: ONRQ_MIGRATING and teaches scheduler to understand it (we need a little changes predominantly in try_to_wake_up()). This will be used in the following way:
(we are changing task's rq)
raw_spin_lock(&src_rq->lock); dequeue_task(src_rq, p, 0); p->on_rq = ONRQ_MIGRATING; set_task_cpu(p, dst_cpu); raw_spin_unlock(&src_rq->lock);
raw_spin_lock(&dst_rq->lock); p->on_rq = ONRQ_QUEUED; enqueue_task(dst_rq, p, 0); raw_spin_unlock(&dst_rq->lock);
Patches [3-5/5] remove double locks and use new ONRQ_MIGRATING state. They allow unlocked using of 3-4 function, which looks safe for me.
The series doesn't add any overhead, and it shouldn't worsen performance, I think. It improves granularity, and it's possible to imagine situations, which will be happier without double rq lock.
I tested the reliability for 2-3 week (in sum, with breaks) on my work laptop, and bugs did not happen. Looks like, it's ready for people's review.
Commentaries are welcome. Thanks!
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Kirill Tkhai (5): sched: Wrapper for checking task_struct's .on_rq sched: Teach scheduler to understand ONRQ_MIGRATING state sched: Remove double_rq_lock() from __migrate_task() sched/fair: Remove double_lock_balance() from active_load_balance_cpu_stop() sched/fair: Remove double_lock_balance() from load_balance()
kernel/sched/core.c | 109 +++++++++++++++++++------------- kernel/sched/deadline.c | 14 ++-- kernel/sched/fair.c | 156 +++++++++++++++++++++++++++++----------------- kernel/sched/rt.c | 16 ++--- kernel/sched/sched.h | 8 ++ kernel/sched/stop_task.c | 2 - 6 files changed, 187 insertions(+), 118 deletions(-)
-- Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
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