From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Andi Kleen <andi@firstfloor.org>
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 23:04:31 +0100 [thread overview]
Message-ID: <1193868271.5911.5.camel@lappy> (raw)
In-Reply-To: <p73bqaf2bpb.fsf@bingen.suse.de>
On Wed, 2007-10-31 at 22:53 +0100, Andi Kleen wrote:
> 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.
Well, me neither, it was just an idea, and a challenge to get
working :-)
next prev parent reply other threads:[~2007-10-31 22:05 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
2007-10-31 22:04 ` Peter Zijlstra [this message]
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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