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From: Peter Zijlstra <peterz@infradead.org>
To: Venki Pallipadi <venki@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Suresh Siddha <suresh.b.siddha@intel.com>,
	Aaron Durbin <adurbin@google.com>, Paul Turner <pjt@google.com>,
	Yong Zhang <yong.zhang0@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Extend mwait idle to optimize away CAL and RES interrupts to an idle CPU -v1
Date: Mon, 27 Feb 2012 09:45:54 +0100	[thread overview]
Message-ID: <1330332354.11248.32.camel@twins> (raw)
In-Reply-To: <CABeCy1a0U8Hk3Yfp54M-U80t2fbPrFQw=GnNQ_V082e9VxJQow@mail.gmail.com>

On Thu, 2012-02-23 at 11:34 -0800, Venki Pallipadi wrote:

> > > +             local_bh_disable();
> > > +             local_irq_disable();
> >
> > That local_bh_disable() is completely superfluous, disabling IRQs
> > already kills bh.
> 
> The reason for local_bh_disable/enable was to check for potential
> softirqs after these interrupt.

Why is that needed? We never wrap local_irq_disable() in bh muck?


> > Why doesn't ipiless_idle_exit() call this? That would keep it isolated
> > to just those idle routines that actually use mwait instead of bothering
> > the generic idle paths with this.
> 
> ipiless_idle_exit is called in the inner most part of idle entry exit.
> In mwait case we may not even have interrupts enabled at that time and
> there is code that does idle residency timing etc which will get
> impacted if we start doing the pending ipi work there. Doing it at
> higher level along with things like enter-exit tickless felt nicer.

But but but, an actual interrupt can be handled before the instruction
after mwait, so why would this be a problem?


  parent reply	other threads:[~2012-02-27  8:46 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-23  0:36 [PATCH] Extend mwait idle to optimize away CAL and RES interrupts to an idle CPU -v1 Venkatesh Pallipadi
2012-02-23  7:50 ` Ingo Molnar
2012-02-23  9:08   ` Peter Zijlstra
2012-02-23 20:04     ` Venki Pallipadi
2012-02-23 20:03   ` Venki Pallipadi
2012-03-02  0:33   ` Venki Pallipadi
2012-03-02  1:28     ` Suresh Siddha
2012-03-02  1:35       ` Venki Pallipadi
2012-03-02  1:37         ` Suresh Siddha
2012-03-02  2:00           ` Venki Pallipadi
2012-03-02  7:21             ` Ingo Molnar
2012-03-02 17:41               ` Suresh Siddha
2012-03-06 21:41                 ` fork_idle from wq cleanup Venkatesh Pallipadi
2012-03-06 21:41                   ` [PATCH 1/5] x86: Move fork_idle from wq and idle caching to common code Venkatesh Pallipadi
2012-03-06 21:41                   ` [PATCH 2/5] ia64: Use common fork_idle_from_wq in smpboot Venkatesh Pallipadi
2012-03-06 21:41                   ` [PATCH 3/5] mips: " Venkatesh Pallipadi
2012-03-06 22:51                     ` Ralf Baechle
2012-03-06 21:41                   ` [PATCH 4/5] powerpc: " Venkatesh Pallipadi
2012-03-06 21:41                   ` [PATCH 5/5] s390: " Venkatesh Pallipadi
2012-03-07  7:00                     ` Heiko Carstens
2012-03-07  6:06                   ` fork_idle from wq cleanup Suresh Siddha
2012-02-23  9:30 ` [PATCH] Extend mwait idle to optimize away CAL and RES interrupts to an idle CPU -v1 Peter Zijlstra
2012-02-23 19:34   ` Venki Pallipadi
2012-02-24  5:41     ` Yong Zhang
2012-02-24  6:13       ` Yong Zhang
2012-02-27  8:38         ` Peter Zijlstra
2012-02-27  9:08           ` Yong Zhang
2012-02-27  9:30             ` Peter Zijlstra
2012-02-27  9:51               ` Yong Zhang
2012-02-26  1:32       ` Paul E. McKenney
2012-02-27  9:06         ` Yong Zhang
2012-02-27 17:05           ` Paul E. McKenney
2012-02-28  7:12             ` Yong Zhang
2012-02-28 13:05               ` Paul E. McKenney
2012-02-29  6:36                 ` Yong Zhang
2012-02-27  8:45     ` Peter Zijlstra [this message]
2012-02-27 18:17       ` Venki Pallipadi

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