linux-kernel - Re: a bug in AS scheduler?

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Message-ID: <45E5A0E4.2000301@cse.ohio-state.edu>
Date:	Wed, 28 Feb 2007 10:33:56 -0500
From:	Xiaoning Ding <dingxn@....ohio-state.edu>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	Benoit Boissinot <bboissin@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: a bug in AS scheduler?

Jens Axboe wrote:
> On Wed, Feb 28 2007, Benoit Boissinot wrote:
>> On 2/28/07, Jens Axboe <jens.axboe@...cle.com> wrote:
>>> On Tue, Feb 27 2007, Xiaoning Ding wrote:
>>>> Hi,
>>>>
>>>> I am reading the source code AS scheduler in 2.6.18(as-ioscheduler.c).
>>>> In function as_close_req, variable delay is in millisecond, while
>>>> ad->antic_expire is in jiffies. Doesn't the comparison of delay and
>>>> ad->antic_expire make any problem?
>>>> The related source code is quoted blow:
>>>>
>>>>       if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
>>>>               delay = 0;
>>>>       else
>>>>               delay = ((jiffies - ad->antic_start) * 1000) / HZ;
>>> antic_start is in jiffies, the difference is here multiplied by 1000 and
>>> divided by HZ to turn it into msecs. so delay is in msecs.
>>>
>> I am pretty sure Xiaoning was talking about antic_expire, particularly
>> this comparison:
>>
>>     else if (delay <= 20 && delay <= ad->antic_expire)
> 
> Ah, I misread the name. That does look like a bug, antic_expire is in
> jiffies.

You got it.

Xiaoning

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