Subject: Re: [PATCH]tickless: Fix tick nohz timer irq0 fail to increaase
From: Peter Zijlstra <peterz@infradead.org>
To: Arjan van de Ven <arjan@infradead.org>
Cc: "Youquan,Song" <youquan.song@linux.intel.com>, hpa@zytor.com,
       tglx@linutronix.de, akpm@linux-foundation.org,
       venkatesh.pallipadi@intel.com, suresh.b.siddha@intel.com,
       kent.liu@intel.com, chaohong.guo@intel.com, youquan.song@intel.com,
       linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
       "jens.axboe" <jens.axboe@oracle.com>
In-Reply-To: <20100104043650.6acfb056@infradead.org>
References: <20091214130233.GA3898@youquan-linux.bj.intel.com>
	 <20100104104905.GA30574@youquan-linux.bj.intel.com>
	 <20100104043650.6acfb056@infradead.org>
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Date: Mon, 04 Jan 2010 15:00:49 +0100
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On Mon, 2010-01-04 at 04:36 -0800, Arjan van de Ven wrote:
> > cause is that it is default to enable high resolution timer which
> > will force to oneshot broadcast mode.
> 
> using local apic in one shot mode is not a problem, I'd in fact call it
> a feature... 

lapic yes, broadcast not so much.

He mentioned he was using Nehelem-EX which is known broken in that it
stops the lapic in deeper C states and thus reverts to HPET broadcast
since there's not enough HPET timers to go around.

Something like processor.max_cstate=2 should fix that IIRC.

Jens ran into this on his shiny new box.

Disabling nohz is funny indeed, one wonders why he does that.

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