linux-kernel - Re: [PATCH 09/12] irq: implement IRQ expecting

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Date:	Mon, 14 Jun 2010 11:46:23 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Jiri Slaby <jirislaby@...il.com>
CC:	mingo@...e.hu, tglx@...utronix.de, bphilips@...e.de,
	yinghai@...nel.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	jeff@...zik.org, linux-ide@...r.kernel.org,
	stern@...land.harvard.edu, gregkh@...e.de, khali@...ux-fr.org
Subject: Re: [PATCH 09/12] irq: implement IRQ expecting

On 06/14/2010 11:43 AM, Tejun Heo wrote:
> Hello,
> 
> On 06/14/2010 11:21 AM, Jiri Slaby wrote:
>> On 06/13/2010 05:31 PM, Tejun Heo wrote:
>>> --- a/kernel/irq/spurious.c
>>> +++ b/kernel/irq/spurious.c
>> ...
>>
>>> @@ -25,9 +26,43 @@ enum {
>>>  	/* IRQ polling common parameters */
>>>  	IRQ_POLL_SLOW_INTV		= 3 * HZ,	/* not too slow for ppl, slow enough for machine */
>>>  	IRQ_POLL_INTV			= HZ / 100,	/* from the good ol' 100HZ tick */
>>> +	IRQ_POLL_QUICK_INTV		= HZ / 1000,	/* pretty quick but not too taxing */
>>>  
>>>  	IRQ_POLL_SLOW_SLACK		= HZ,
>>>  	IRQ_POLL_SLACK			= HZ / 1000,	/* 10% slack */
>>> +	IRQ_POLL_QUICK_SLACK		= HZ / 10000,	/* 10% slack */
>>
>> Hi. These are zeros on most systems (assuming distros set HZ=100 and
>> 250), what is their purpose then?
> 
> On every tick and no slack.  :-)

Hmmm... but yeah, it would be better to make IRQ_POLL_SLACK HZ / 250
so that we at least have one tick slack on 250HZ configs which are
pretty common these days.

Thanks.

-- 
tejun
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