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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 04 Apr 2014 14:14:26 -0400
From:	"Marcos E. Matsunaga" <Marcos.Matsunaga@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Waiman Long <waiman.long@...com>
CC:	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

Attached is the .config I used.

On 04/04/2014 12:55 PM, Konrad Rzeszutek Wilk wrote:
> On Thu, Apr 03, 2014 at 10:57:18PM -0400, Waiman Long wrote:
>> On 04/03/2014 01:23 PM, Konrad Rzeszutek Wilk wrote:
>>> On Wed, Apr 02, 2014 at 10:10:17PM -0400, Waiman Long wrote:
>>>> On 04/02/2014 04:35 PM, Waiman Long wrote:
>>>>> 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.
>>>>>
>>>> BTW, does the halting and sending IPI mechanism work in HVM? I saw
>>> Yes.
>>>> that in RHEL7, PV spinlock was explicitly disabled when in HVM mode.
>>>> However, this piece of code isn't in upstream code. So I wonder if
>>>> there is problem with that.
>>> The PV ticketlock fixed it for HVM. It was disabled before because
>>> the PV guests were using bytelocks while the HVM were using ticketlocks
>>> and you couldnt' swap in PV bytelocks for ticketlocks during startup.
>> The RHEL7 code has used PV ticketlock already. RHEL7 uses a single
>> kernel for all configurations. So PV ticketlock as well as Xen and
>> KVM support was compiled in. I think booting the kernel on bare
>> metal will cause the Xen code to work in HVM mode thus activating
>> the PV spinlock code which has a negative impact on performance.
> Huh? -EPARSE
>
>> That may be why it was disabled so that the bare metal performance
>> will not be impacted.
> I am not following you.
>> BTW, could you send me more information about the configuration of
>> the machine, like the .config file that you used?
> Marcos, could you please send that information to Peter. Thanks!
>> -Longman

-- 

Regards,

Marcos Eduardo Matsunaga

Oracle USA
Linux Engineering

“The statements and opinions expressed here are my own and do not
necessarily represent those of Oracle Corporation.”


View attachment "config-3.14.0-qspinlockV8+" of type "text/plain" (125954 bytes)