linux-kernel - Re: [patch] CFS scheduler, -v14

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Message-ID: <20070601192142.GA10039@elte.hu>
Date:	Fri, 1 Jun 2007 21:21:42 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Li Yu <raise.sail@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [patch] CFS scheduler, -v14


* Li Yu <raise.sail@...il.com> wrote:

> Also, I have want to know what's real meaning of
> 
>    add_wait_runtime(rq, curr, delta_mine - delta_exec);
> 
> in update_curr(), IMHO, it should be
> 
>    add_wait_runtime(rq, curr, delta_mine - delta_fair);
> 
> Is this just another heuristics? or my opinion is wrong again? :-)

well, ->wait_runtime is in real time units. If a task executes 
delta_exec time on the CPU, we deduct "-delta_exec" 1:1. But during that 
time the task also got entitled to a bit more CPU time, that is 
+delta_mine. The calculation above expresses this. I'm not sure what 
sense '-delta_fair' would make - "delta_fair" is the amount of time a 
nice-0 task would be entitled to - but this task might not be a nice-0 
task. Furthermore, even for a nice-0 task why deduct -delta_fair - it 
spent delta_exec on the CPU.

	Ingo
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