linux-kernel - Re: [PATCH]tickless: Fix tick nohz timer irq0 fail to increaase

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Message-ID: <20100104043650.6acfb056@infradead.org>
Date:	Mon, 4 Jan 2010 04:36:50 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Youquan,Song" <youquan.song@...ux.intel.com>
Cc:	hpa@...or.com, tglx@...utronix.de, akpm@...ux-foundation.org,
	venkatesh.pallipadi@...el.com, suresh.b.siddha@...el.com,
	kent.liu@...el.com, chaohong.guo@...el.com, youquan.song@...el.com,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH]tickless: Fix tick nohz timer irq0 fail to increaase

On Mon, 4 Jan 2010 05:49:05 -0500
"Youquan,Song" <youquan.song@...ux.intel.com> wrote:

> Tickless is disabled by nohz=off, which is used in OSVs.

it is? I doubt anyone wants to normally disable tickless, the power
cost is just too high....

> But in
> current kernel, if tickless is disabled, the timer irq0 will not
> increase.

why is this a problem? 

> Because the timer event handler should be
> tick_handle_periodic, but actually event handler keep as
> tick_handle_oneshot_broadcast which is used in tickless. The root
> 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...


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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