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Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS
From: Peter Zijlstra <peterz@infradead.org>
To: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Avi Kivity <avi@redhat.com>,
        Rik van Riel <riel@redhat.com>, linux-kernel@vger.kernel.org,
        vatsa@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com
Date: Mon, 20 Feb 2012 11:51:13 +0100
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On Mon, 2012-02-20 at 13:38 +0530, Nikunj A Dadhania wrote:
> +#ifdef CONFIG_PARAVIRT_FLUSH_TLB
> +               while (!cpumask_empty(to_cpumask(f->flush_cpumask)) && --loop)
> +                       cpu_relax();
> +               if (!loop && !cpumask_empty(to_cpumask(f->flush_cpumask)))
> +                       halt();


That's just vile, you don't need to wait for it, all you need to make
sure is that when that vcpu wakes up it does the flush.

But yeah, the results are a good hint that you're on the right track.