linux-kernel - Re: [ckrm-tech] [RFC] [PATCH 0/3] Add group fairness to CFS

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Message-ID: <20070531085600.GA9826@in.ibm.com>
Date:	Thu, 31 May 2007 14:26:00 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	William Lee Irwin III <wli@...omorphy.com>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	ckrm-tech@...ts.sourceforge.net, efault@....de,
	linux-kernel@...r.kernel.org, tingy@...umass.edu,
	Peter Williams <pwil3058@...pond.net.au>, kernel@...ivas.org,
	tong.n.li@...el.com, containers@...ts.osdl.org,
	Ingo Molnar <mingo@...e.hu>, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, Guillaume Chazarain <guichaz@...oo.fr>
Subject: Re: [ckrm-tech] [RFC] [PATCH 0/3] Add group fairness to CFS

On Thu, May 31, 2007 at 02:03:53PM +0530, Srivatsa Vaddagiri wrote:
> Its ->wait_runtime will drop less significantly, which lets it be
> inserted in rb-tree much to the left of those 1000 tasks (and which indirectly
> lets it gain back its fair share during subsequent schedule cycles).
> 
> Hmm ..is that the theory?

My only concern is the time needed to converge to this fair
distribution, especially in face of fluctuating workloads. For ex: a
container who does a fork bomb can have a very adverse impact on other
container's fair share under this scheme compared to other schemes which 
dedicate separate rb-trees for differnet containers (and which also support two 
level hierarchical scheduling inside the core scheduler).

I am inclined to have the core scheduler support atleast two levels of 
hierarchy (to better isolate each container) and resort to the flattening 
trick for higher levels.

-- 
Regards,
vatsa
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