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Date: Wed, 15 Nov 2017 13:11:52 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Quan Xu <quan.xu03@gmail.com>
Cc: kvm@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
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        Tobias Klauser <tklauser@distanz.ch>
Subject: Re: [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter
 real idle path
Message-ID: <20171115121152.gqug5wzerlo3eimd@hirez.programming.kicks-ass.net>
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On Mon, Nov 13, 2017 at 06:06:02PM +0800, Quan Xu wrote:
> From: Yang Zhang <yang.zhang.wz@gmail.com>
> 
> Implement a generic idle poll which resembles the functionality
> found in arch/. Provide weak arch_cpu_idle_poll function which
> can be overridden by the architecture code if needed.

No, we want less of those magic hooks, not more.

> Interrupts arrive which may not cause a reschedule in idle loops.
> In KVM guest, this costs several VM-exit/VM-entry cycles, VM-entry
> for interrupts and VM-exit immediately. Also this becomes more
> expensive than bare metal. Add a generic idle poll before enter
> real idle path. When a reschedule event is pending, we can bypass
> the real idle path.

Why not do a HV specific idle driver?