linux-kernel - Re: [RFC PATCH 0/4] Gang scheduling in CFS

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Message-ID: <874nww2egt.fsf@abhimanyu.in.ibm.com>
Date:	Tue, 20 Dec 2011 07:26:18 +0530
From:	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org,
	vatsa@...ux.vnet.ibm.com, bharata@...ux.vnet.ibm.com,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	paulus <paulus@...ba.org>
Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS

On Mon, 19 Dec 2011 16:51:41 +0100, Peter Zijlstra <peterz@...radead.org> wrote:
> 
> Anyway, I had a look at your patches and I don't see how could ever
> work. You gang-schedule cgroup entities, but there's no guarantee the
> load-balancer will have at least one task for each group on every cpu.
>
As stated earlier:

    The gang scheduling problem can be broken into two parts:
    a) Placement of the tasks to be gang scheduled 
    b) Synchronized scheduling of the tasks across a subset of cpu.

In the patch, I have (b) implemented and placement is done by pinning
the vcpu of a VM in userspace. Yes, thats not the right way. 

Effectively, no trouble to the load-balancer here.

Nikunj

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