linux-kernel - Re: [PATCH 1/5] Revert recent removal of set_curr

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Date:	Mon, 24 Sep 2007 18:35:25 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Cc:	akpm@...ux-foundation.org, dmitry.adamushko@...il.com,
	linux-kernel@...r.kernel.org, dhaval@...ux.vnet.ibm.com,
	containers@...ts.osdl.org, kamezawa.hiroyu@...fujitsu.com,
	menage@...gle.com, efault@....de
Subject: Re: [PATCH 1/5] Revert recent removal of set_curr_task()


* Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> wrote:

> > (3) rework enqueue/dequeue_entity() to get rid of
> > sched_class::set_curr_task()
> 
> Dmitry/Ingo,
> 	I am sorry for not having reviewed this change properly, but I 
> think we need to revert this.

ah, i was wondering about that already. We can certainly skip that 
optimization.

> In theory its possible to solve these problems w/o reintroducing 
> set_curr_task(). I tried doing so, but found it clutters 
> dequeue_entity and enqueue_entity a lot and makes it less readable. It 
> will duplicate what put_prev_entity() and set_next_entity() are 
> supposed to do. Moreoever it is slightly inefficient to do all these 
> in dequeue_entity() if we consider that dequeue_entity can be called 
> on current task for other reasons as well (like when it is abt to 
> sleep or change its nice value).

yeah, it's not worth it. I'd go for keeping the code unified even if 
adds a few instructions runtime overhead, as i'd expect most distros to 
enable fair-group-scheduling by default in the future. (once all the 
containers infrastructure and tools has trickled down to them)

	Ingo
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