Message-ID: <5474863A.6010307@redhat.com>
Date: Tue, 25 Nov 2014 08:38:02 -0500
From: Rik van Riel <riel@redhat.com>
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To: Davidlohr Bueso <dave@stgolabs.net>
CC: Khalid Aziz <khalid.aziz@oracle.com>, tglx@linutronix.de, corbet@lwn.net,
        mingo@redhat.com, hpa@zytor.com, peterz@infradead.org,
        akpm@linux-foundation.org, rientjes@google.com, ak@linux.intel.com,
        mgorman@suse.de, liwanp@linux.vnet.ibm.com, raistlin@linux.it,
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Subject: Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice
 (was: Pre-emption control for userspace)
References: <1416862595-24513-1-git-send-email-khalid.aziz@oracle.com>	 <5473E388.6000605@redhat.com> <1416897050.20575.18.camel@linux-t7sj.site>
In-Reply-To: <1416897050.20575.18.camel@linux-t7sj.site>
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On 11/25/2014 01:30 AM, Davidlohr Bueso wrote:
> 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.

How many people are going to build two different binaries,
one for bare metal, and one for virtualized environments?

I suspect the vast majority of applications will only be
built once, and it would be nice if it wasn't using a
locking scheme that broke horribly on a significant part
of the deployments...

- -- 
All rights reversed
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