Re: [PATCH] Documentation/scheduler/sched-deadline.txt: correct definition of density as C_i/min{D_i,P_i}

From: Juri Lelli <juri.lelli@arm.com>
To: Luca Abeni <luca.abeni@unitn.it>,
	Zhiqiang Zhang <zhangzhiqiang.zhang@huawei.com>
Cc: "henrik@austad.us" <henrik@austad.us>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>
Subject: Re: [PATCH] Documentation/scheduler/sched-deadline.txt: correct definition of density as C_i/min{D_i,P_i}
Date: Wed, 08 Apr 2015 10:31:46 +0100	[thread overview]
Message-ID: <5524F582.5020201@arm.com> (raw)
In-Reply-To: <20150403125237.45b38a71@luca-1225C>

Hi Luca,

On 03/04/15 11:52, Luca Abeni wrote:
> Hi,
> 
> On Fri, 3 Apr 2015 16:18:33 +0800
> Zhiqiang Zhang <zhangzhiqiang.zhang@huawei.com> wrote:
> 
>> >From the contex,the definition of the destiny of a task
>> C_i/min{D_i,T_i},where T_i is not referred before, should be
>> substituted by C_i/min{D_i,P_i}.
> You are right, "T_i" should be substituted with "P_i"...
> But now that I look at it more carefully, I think that "C_i" is also
> wrong... It should be "WCET_i".
> 
> 
> BTW, speaking about documentation: I still have some SCHED_DEADLINE
> documentation patches in my local tree... I'll update and send them in
> next week. Juri, should I send the patches to you, or submit directly
> to the mailing list?
> 

As you prefer, I'll review them anyway :). I guess you can just
send them on the list if you like, so that you'll receive more
comments in one go.

Thanks a lot,

- Juri

> 			Thanks,
> 				Luca
>>
>> ----------------------------------------
>>
>> Signed-off-by: Zhiqiang Zhang <zhangzhiqiang.zhang@huawei.com>
>> ---
>>  Documentation/scheduler/sched-deadline.txt | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/scheduler/sched-deadline.txt
>> b/Documentation/scheduler/sched-deadline.txt index 21461a0..194664b
>> 100644 --- a/Documentation/scheduler/sched-deadline.txt
>> +++ b/Documentation/scheduler/sched-deadline.txt
>> @@ -169,8 +169,8 @@ CONTENTS
>>   of all the tasks executing on a CPU if and only if the total
>> utilisation of the tasks running on such a CPU is smaller or equal
>> than 1. If D_i != P_i for some task, then it is possible to define
>> the density of
>> - a task as C_i/min{D_i,T_i}, and EDF is able to respect all the
>> deadlines
>> - of all the tasks running on a CPU if the sum sum_i C_i/min{D_i,T_i}
>> of the
>> + a task as C_i/min{D_i,P_i}, and EDF is able to respect all the
>> deadlines
>> + of all the tasks running on a CPU if the sum sum_i C_i/min{D_i,P_i}
>> of the densities of the tasks running on such a CPU is smaller or
>> equal than 1 (notice that this condition is only sufficient, and not
>> necessary). 
> 