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From: Thomas Gleixner <tglx@linutronix.de>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: "Pan, Jacob jun" <jacob.jun.pan@intel.com>,
	Preeti U Murthy <preeti@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Viresh Kumar <viresh.kumar@linaro.org>, LKP <lkp@01.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Zhang, Rui" <rui.zhang@intel.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Eduardo Valentin <edubezval@gmail.com>,
	"Van De Ven, Arjan" <arjan.van.de.ven@intel.com>
Subject: Re: [PATCH] tick/powerclamp: Remove tick_nohz_idle abuse
Date: Fri, 19 Dec 2014 20:56:23 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.11.1412192054130.17382@nanos> (raw)
In-Reply-To: <20141219103900.101f6c6d@jacob-VirtualBox>

On Fri, 19 Dec 2014, Jacob Pan wrote:

> On Thu, 18 Dec 2014 22:12:57 +0100 (CET)
> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > On Thu, 18 Dec 2014, Jacob Pan wrote:
> > > OK I agree, also as I mentioned earlier, Peter already has a patch
> > > for consolidated idle loop and remove tick_nohz_idle_enter/exit
> > > call from powerclamp driver. I have been working on a few tweaks to
> > > maintain the functionality and efficiency with the consolidated
> > > idle loop. We can apply the patches on top of yours.
> > 
> > No. This is equally wrong as I pointed out before. The 'unified' idle
> > loop is still fake and just pretending to be idle.
> > 
> In terms of efficiency, the consolidated idle loop will allow turning
> off sched tick during idle injection period. If we just take out the
> tick_nohz_idle_xxx call, the effectiveness of powerclamp is going down
> significantly. I am not arguing the design but from fixing regression
> perspective or short term solution.

There is no perspective. Period.

Its violates every rightful assumption of the nohz_IDLE_* code and
just ever worked by chance. There is so much subtle wreckage lurking
there that the only sane solution is to forbid it. End of story.

Thanks,

	tglx

WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: lkp@lists.01.org
Subject: Re: [PATCH] tick/powerclamp: Remove tick_nohz_idle abuse
Date: Fri, 19 Dec 2014 20:56:23 +0100	[thread overview]
Message-ID: <alpine.DEB.2.11.1412192054130.17382@nanos> (raw)
In-Reply-To: <20141219103900.101f6c6d@jacob-VirtualBox>

[-- Attachment #1: Type: text/plain, Size: 1266 bytes --]

On Fri, 19 Dec 2014, Jacob Pan wrote:

> On Thu, 18 Dec 2014 22:12:57 +0100 (CET)
> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > On Thu, 18 Dec 2014, Jacob Pan wrote:
> > > OK I agree, also as I mentioned earlier, Peter already has a patch
> > > for consolidated idle loop and remove tick_nohz_idle_enter/exit
> > > call from powerclamp driver. I have been working on a few tweaks to
> > > maintain the functionality and efficiency with the consolidated
> > > idle loop. We can apply the patches on top of yours.
> > 
> > No. This is equally wrong as I pointed out before. The 'unified' idle
> > loop is still fake and just pretending to be idle.
> > 
> In terms of efficiency, the consolidated idle loop will allow turning
> off sched tick during idle injection period. If we just take out the
> tick_nohz_idle_xxx call, the effectiveness of powerclamp is going down
> significantly. I am not arguing the design but from fixing regression
> perspective or short term solution.

There is no perspective. Period.

Its violates every rightful assumption of the nohz_IDLE_* code and
just ever worked by chance. There is so much subtle wreckage lurking
there that the only sane solution is to forbid it. End of story.

Thanks,

	tglx

  reply	other threads:[~2014-12-19 19:56 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-18 10:51 [PATCH] tick/powerclamp: Remove tick_nohz_idle abuse Thomas Gleixner
2014-12-18 10:51 ` Thomas Gleixner
2014-12-18 14:01 ` Eduardo Valentin
2014-12-18 14:01   ` Eduardo Valentin
2014-12-18 14:43   ` Thomas Gleixner
2014-12-18 14:43     ` Thomas Gleixner
2014-12-18 17:28 ` Preeti U Murthy
2014-12-18 17:28   ` Preeti U Murthy
     [not found]   ` <DD415AA12F8FF042BF4EA69DF123C1478AF91730@ORSMSX101.amr.corp.intel.com>
2014-12-18 19:52     ` Jacob Pan
2014-12-18 19:52       ` Jacob Pan
2014-12-18 21:12       ` Thomas Gleixner
2014-12-18 21:12         ` Thomas Gleixner
2014-12-19 18:39         ` Jacob Pan
2014-12-19 18:39           ` Jacob Pan
2014-12-19 19:56           ` Thomas Gleixner [this message]
2014-12-19 19:56             ` Thomas Gleixner
2014-12-20  1:31             ` Preeti U Murthy
2014-12-20  1:31               ` Preeti U Murthy
2014-12-23  2:57               ` Jacob Pan
2014-12-23  2:57                 ` Jacob Pan
2014-12-31  5:04                 ` Preeti U Murthy
2014-12-31  5:04                   ` Preeti U Murthy
2014-12-19 13:09 ` [tip:timers/urgent] " tip-bot for Thomas Gleixner
2014-12-19 13:09   ` tip-bot for Thomas Gleixner

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