linux-kernel - Re: [RFC v4 PATCH 6/7] sched: Rebalance cfs runtimes

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Message-ID: <1259942998.17907.897.camel@laptop>
Date:	Fri, 04 Dec 2009 17:09:58 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	bharata@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Avi Kivity <avi@...hat.com>,
	Chris Friesen <cfriesen@...tel.com>,
	Paul Menage <menage@...gle.com>,
	Mike Waychison <mikew@...gle.com>
Subject: Re: [RFC v4 PATCH 6/7] sched: Rebalance cfs runtimes

On Tue, 2009-11-17 at 20:07 +0530, Bharata B Rao wrote:
> sched: CFS runtime borrowing
> 
> From: Bharata B Rao <bharata@...ux.vnet.ibm.com>
> 
> Before throttling a group, try to borrow runtime from groups that have excess.
> 
> To start with, a group will get equal runtime on every cpu. If the group doesn't
> have tasks on all cpus, it might get throttled on some cpus while it still has
> runtime left on other cpus where it doesn't have any tasks to consume that
> runtime. Hence there is a chance to borrow runtimes from such cpus/cfs_rqs to
> cpus/cfs_rqs where it is required.
> 
> CHECK: RT seems to be handling runtime initialization/reclaim during hotplug
> from multiple places (migration_call, update_runtime). Need to check if CFS
> also needs to do the same.
> 
> Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
> ---
>  kernel/sched.c      |   26 ++++++++
>  kernel/sched_fair.c |  172 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  kernel/sched_rt.c   |   26 +-------
>  3 files changed, 202 insertions(+), 22 deletions(-)

I think that if we unify the se/rq bandwidth structures a lot of copy
and paste can be avoided, resulting in an over-all much easier to
maintain code-base.

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