Re: [RFC][PATCH 0/5] Reduce runqueue lock contention -v2

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From: Frank Rowand
Date: Thursday, December 16, 2010 - 1:45 pm

On 12/16/10 11:42, Peter Zijlstra wrote:

Yes.  (This is the answer when only the first patch is applied.)

The wakeup is bounced to the previous task cpu.  The bounce adds extra
overhead (including an IRQ on the previous task cpu) in return for a
reduction in the number of rq->lock contentions.

Then the try_to_wake_up() on the previous task cpu may wake the task
on a different cpu, but the bias should be the cpu that try_to_wake_up()
is now running on.

The second patch in my series instead feeds the waking cpu number to
select_task_rq(), so the bias will be to wake the task on the waking
cpu.

-Frank

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Messages in current thread:
[RFC][PATCH 0/5] Reduce runqueue lock contention -v2, Peter Zijlstra, (Thu Dec 16, 7:56 am)
[RFC][PATCH 1/5] sched: Always provide p->oncpu, Peter Zijlstra, (Thu Dec 16, 7:56 am)
[RFC][PATCH 3/5] sched: Change the ttwu success details, Peter Zijlstra, (Thu Dec 16, 7:56 am)
[RFC][PATCH 4/5] sched: Clean up ttwu stats, Peter Zijlstra, (Thu Dec 16, 7:56 am)
[RFC][PATCH 5/5] sched: Reduce ttwu rq->lock contention, Peter Zijlstra, (Thu Dec 16, 7:56 am)
Re: [RFC][PATCH 3/5] sched: Change the ttwu success details, Frederic Weisbecker, (Thu Dec 16, 8:23 am)
Re: [RFC][PATCH 5/5] sched: Reduce ttwu rq->lock contention, Frederic Weisbecker, (Thu Dec 16, 8:31 am)
Re: [RFC][PATCH 3/5] sched: Change the ttwu success details, Frederic Weisbecker, (Thu Dec 16, 8:35 am)
Re: [RFC][PATCH 3/5] sched: Change the ttwu success details, Frederic Weisbecker, (Thu Dec 16, 8:45 am)
Re: [RFC][PATCH 0/5] Reduce runqueue lock contention -v2, Frank Rowand, (Thu Dec 16, 12:12 pm)
Re: [RFC][PATCH 0/5] Reduce runqueue lock contention -v2, Frank Rowand, (Thu Dec 16, 12:36 pm)
Re: [RFC][PATCH 0/5] Reduce runqueue lock contention -v2, Frank Rowand, (Thu Dec 16, 12:36 pm)
Re: [RFC][PATCH 0/5] Reduce runqueue lock contention -v2, Frank Rowand, (Thu Dec 16, 12:39 pm)
Re: [RFC][PATCH 0/5] Reduce runqueue lock contention -v2, Peter Zijlstra, (Thu Dec 16, 12:42 pm)
Re: [RFC][PATCH 0/5] Reduce runqueue lock contention -v2, Frank Rowand, (Thu Dec 16, 1:45 pm)
Re: [RFC][PATCH 1/5] sched: Always provide p->oncpu, Frank Rowand, (Fri Dec 17, 6:03 pm)
Re: [RFC][PATCH 4/5] sched: Clean up ttwu stats, Frank Rowand, (Fri Dec 17, 6:09 pm)