linux-kernel - Re: [PATCH] sky2: Use deferrable timer for watchdog

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Message-ID: <Pine.LNX.4.64.0712202115320.5453@bizon.gios.gov.pl>
Date:	Thu, 20 Dec 2007 21:17:45 +0100 (CET)
From:	Krzysztof Oledzki <olel@....pl>
To:	Parag Warudkar <parag.warudkar@...il.com>
cc:	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	netdev@...r.kernel.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sky2: Use deferrable timer for watchdog



On Thu, 20 Dec 2007, Parag Warudkar wrote:

> On Dec 20, 2007 2:22 PM, Kok, Auke <auke-jan.h.kok@...el.com> wrote:
>> ok, that's just bad and if there's no user-defineable limit to the deferral I
>> definately don't like this change.
>>
>> Can I safely assume that any irq will cause all deferred timers to run?
>
> I think even other causes for wakeup like process related ones will
> cause the CPU to go busy and run the timers.
> This, coupled with the fact that no one is yet able to reach 0 wakeups
> per second makes it pretty unlikely that deferrable timers will be
> deferred indefinitely.
>
>>
>> If this is the case then for e1000 this patch is still OK since the watchdog needs
>> to run (1) after a link up/down interrupt or (2) to update statistics. Those
>> statistics won't increase if there is no traffic of course...
>>
>
> I think it is reasonable for Network driver watchdogs to use a
> deferrable timer - if the machine is 100% IDLE there is no one needing
> the network to be up.

Please note tha being connected to a network does not only mean to send 
but also to receive.

Best regards,

 				Krzysztof Oledzki
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