linux-kernel - Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support

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Date:	Wed, 02 Apr 2014 16:35:17 -0400
From:	Waiman Long <waiman.long@...com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Marcos Matsunaga <Marcos.Matsunaga@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	xen-devel@...ts.xenproject.org, kvm@...r.kernel.org,
	Paolo Bonzini <paolo.bonzini@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Scott J Norton <scott.norton@...com>,
	Chegu Vinod <chegu_vinod@...com>, boris.ostrovsky@...cle.com
Subject: Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support

On 04/02/2014 10:32 AM, Konrad Rzeszutek Wilk wrote:
> On Wed, Apr 02, 2014 at 09:27:29AM -0400, Waiman Long wrote:
>> N.B. Sorry for the duplicate. This patch series were resent as the
>>       original one was rejected by the vger.kernel.org list server
>>       due to long header. There is no change in content.
>>
>> v7->v8:
>>    - Remove one unneeded atomic operation from the slowpath, thus
>>      improving performance.
>>    - Simplify some of the codes and add more comments.
>>    - Test for X86_FEATURE_HYPERVISOR CPU feature bit to enable/disable
>>      unfair lock.
>>    - Reduce unfair lock slowpath lock stealing frequency depending
>>      on its distance from the queue head.
>>    - Add performance data for IvyBridge-EX CPU.
> FYI, your v7 patch with 32 VCPUs (on a 32 cpu socket machine) on an
> HVM guest under Xen after a while stops working. The workload
> is doing 'make -j32' on the Linux kernel.
>
> Completely unresponsive. Thoughts?
>

Thank for reporting that. I haven't done that much testing on Xen. My 
focus was in KVM. I will perform more test on Xen to see if I can 
reproduce the problem.

-Longman
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