From: Rik van Riel <riel@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <Waiman.Long@hp.com>,
linux-arch@vger.kernel.org,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Oleg Nesterov <oleg@redhat.com>,
kvm@vger.kernel.org,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Daniel J Blueman <daniel@numascale.com>,
x86@kernel.org, Paolo Bonzini <paolo.bonzini@gmail.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Scott J Norton <scott.norton@hp.com>,
Ingo Molnar <mingo@redhat.com>,
David Vrabel <david.vrabel@citrix.com>,
"H. Peter Anvin" <hpa@zytor.com>,
xen-devel@lists.xenproject.org,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Douglas Hatch <doug.hatch@hp.com>
Subject: Re: [PATCH v15 16/16] unfair qspinlock: a queue based unfair lock
Date: Thu, 09 Apr 2015 10:30:02 -0400 [thread overview]
Message-ID: <55268CEA.70303@redhat.com> (raw)
In-Reply-To: <20150409141348.GX5029@twins.programming.kicks-ass.net>
On 04/09/2015 10:13 AM, Peter Zijlstra wrote:
> On Thu, Apr 09, 2015 at 09:16:24AM -0400, Rik van Riel wrote:
>> On 04/09/2015 03:01 AM, Peter Zijlstra wrote:
>>> 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?
>>
>> There are some people out there running guests with dozens
>> of vCPUs. If the code exists to make those setups run better,
>> is there a good reason not to use it?
>
> Well use paravirt, !paravirt stuff sucks performance wise anyhow.
>
> The question really is: is the added complexity worth the maintenance
> burden. And I'm just not convinced !paravirt virt is a performance
> critical target.
Fair enough.
next prev parent reply other threads:[~2015-04-09 14:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-08 18:32 [PATCH v15 16/16] unfair qspinlock: a queue based unfair lock Waiman Long
2015-04-09 7:01 ` Peter Zijlstra
[not found] ` <20150409070146.GL27490@worktop.programming.kicks-ass.net>
2015-04-09 13:16 ` Rik van Riel
[not found] ` <55267BA8.9060009@redhat.com>
2015-04-09 14:13 ` Peter Zijlstra
2015-04-09 14:30 ` Rik van Riel [this message]
2015-04-09 21:52 ` Waiman Long
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