linux-kernel - Re: [PATCH RFC] sched: deferred set priority (dprio)

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Message-ID: <20140803173031.GQ18735@two.firstfloor.org>
Date:	Sun, 3 Aug 2014 19:30:31 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Sergey Oboguev <oboguev.public@...il.com>
Cc:	Mike Galbraith <umgwanakikbuti@...il.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	khalid.aziz@...cle.com
Subject: Re: [PATCH RFC] sched: deferred set priority (dprio)

> (One example might be virtual machine that runs guest operating system that is
> not paravirtualized or can be paravirtualized only to a limited extent. The VM
> might guess that preemption of VCPU thread that is processing events such as
> IPI interrupts, clock interrupts or certain device interrupts is likely to
> cause overall performance degradation due to other VCPUs spinning for an IPI
> response or spinning waiting for a spinlock, and thought the general kinds of
> these dependencies may be foreseen, but actual dependency chains between VCPUs
> cannot be established at run time.)

PAUSE loop exiting (PLE) can handle it in limited fashion on VMs
even without paravirtualization.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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