From: Andi Kleen <andi@firstfloor.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Mike Galbraith <efault@gmx.de>,
Dmitry Adamushko <dmitry.adamushko@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 3/6] sched: high-res preemption tick
Date: Wed, 31 Oct 2007 22:53:04 +0100 [thread overview]
Message-ID: <p73bqaf2bpb.fsf@bingen.suse.de> (raw)
In-Reply-To: <20071031211249.142859000@chello.nl> (Peter Zijlstra's message of "Wed\, 31 Oct 2007 22\:10\:33 +0100")
Peter Zijlstra <a.p.zijlstra@chello.nl> writes:
> Use HR-timers (when available) to deliver an accurate preemption tick.
>
> The regular scheduler tick that runs at 1/HZ can be too coarse when nice
> level are used. The fairness system will still keep the cpu utilisation 'fair'
> by then delaying the task that got an excessive amount of CPU time but try to
> minimize this by delivering preemption points spot-on.
This might be costly when hrtimers happen to use an more expensive
to reprogram time source. Even an APIC timer access is fairly slow.
And you'll potentially add the to lots of context switces.
Not sure that is a good idea for performance in general.
-Andi
next prev parent reply other threads:[~2007-10-31 21:53 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-31 21:10 [PATCH 0/6] various scheduler patches Peter Zijlstra
2007-10-31 21:10 ` [PATCH 1/6] sched: move the group scheduling primitives around Peter Zijlstra
2007-10-31 21:10 ` [PATCH 2/6] sched: make sched_slice() group scheduling savvy Peter Zijlstra
2007-11-01 11:31 ` Srivatsa Vaddagiri
2007-11-01 11:51 ` Peter Zijlstra
2007-11-01 11:58 ` Peter Zijlstra
2007-11-01 12:03 ` Peter Zijlstra
2007-11-01 12:20 ` Peter Zijlstra
2007-11-01 16:31 ` Srivatsa Vaddagiri
2007-11-01 16:55 ` Peter Zijlstra
2007-10-31 21:10 ` [PATCH 3/6] sched: high-res preemption tick Peter Zijlstra
2007-10-31 21:53 ` Andi Kleen [this message]
2007-10-31 22:04 ` Peter Zijlstra
2007-11-01 10:12 ` Peter Zijlstra
2007-10-31 21:10 ` [PATCH 4/6] sched: sched_rt_entity Peter Zijlstra
2007-10-31 21:10 ` [PATCH 5/6] sched: SCHED_FIFO/SCHED_RR watchdog timer Peter Zijlstra
2007-10-31 21:49 ` Andi Kleen
2007-10-31 22:03 ` Peter Zijlstra
2007-11-03 18:16 ` Andi Kleen
2007-10-31 21:10 ` [PATCH 6/6] sched: place_entity() comments Peter Zijlstra
2007-11-01 8:29 ` [PATCH 0/6] various scheduler patches Ingo Molnar
2007-11-01 10:08 ` Peter Zijlstra
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