linux-kernel - Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice (was: Pre-emption control for userspace)

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Date:	Mon, 24 Nov 2014 22:30:50 -0800
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Rik van Riel <riel@...hat.com>
Cc:	Khalid Aziz <khalid.aziz@...cle.com>, tglx@...utronix.de,
	corbet@....net, mingo@...hat.com, hpa@...or.com,
	peterz@...radead.org, akpm@...ux-foundation.org,
	rientjes@...gle.com, ak@...ux.intel.com, mgorman@...e.de,
	liwanp@...ux.vnet.ibm.com, raistlin@...ux.it,
	kirill.shutemov@...ux.intel.com, atomlin@...hat.com,
	avagin@...nvz.org, gorcunov@...nvz.org, serge.hallyn@...onical.com,
	athorlton@....com, oleg@...hat.com, vdavydov@...allels.com,
	daeseok.youn@...il.com, keescook@...omium.org,
	yangds.fnst@...fujitsu.com, sbauer@....utah.edu,
	vishnu.ps@...sung.com, axboe@...com, paulmck@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a
 timeslice (was: Pre-emption control for userspace)

On Mon, 2014-11-24 at 21:03 -0500, Rik van Riel wrote:
> I can see this "solution" help mostly with userspace spinlocks,
> which are relics of a past era that need to die. There is no
> way userspace spinlocks will not fail miserably on virtual
> machines, and it is time to get rid of them.

No, not really. Spinlocks are still very useful on bare metal.
Virtualization is not the only thing out there.

Thanks,
Davidlohr

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