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Date: Thu, 9 Apr 2015 09:01:46 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <Waiman.Long@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, linux-arch@vger.kernel.org,
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        Linus Torvalds <torvalds@linux-foundation.org>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
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        Douglas Hatch <doug.hatch@hp.com>
Subject: Re: [PATCH v15 16/16] unfair qspinlock: a queue based unfair lock
Message-ID: <20150409070146.GL27490@worktop.programming.kicks-ass.net>
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On Wed, Apr 08, 2015 at 02:32:19PM -0400, Waiman Long wrote:
> For a virtual guest with the qspinlock patch, a simple unfair byte lock
> will be used if PV spinlock is not configured in or the hypervisor
> isn't either KVM or Xen. The byte lock works fine with small guest
> of just a few vCPUs. On a much larger guest, however, byte lock can
> have serious performance problem.

Who cares?