From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH] x86 kconfig: Add recommendation to enable paravirt spinlock Date: Mon, 21 Oct 2013 12:30:38 -0400 Message-ID: <20131021163038.GA17709@phenom.dumpdata.com> References: <1382371508-3843-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: mingo@redhat.com, hpa@zytor.com, x86@kernel.org, gleb@redhat.com, pbonzini@redhat.com, tglx@linutronix.de, linux@eikelenboom.it, linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: Raghavendra K T Return-path: Content-Disposition: inline In-Reply-To: <1382371508-3843-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, Oct 21, 2013 at 09:35:08PM +0530, Raghavendra K T wrote: > Since paravirt spinlock optimization are in 3.12 kernel, we have > very good performance benefit for paravirtualized KVM / Xen kernel. > Also we no longer suffer from 5% side effect on native kernel. Yeey! > > Signed-off-by: Raghavendra K T > --- > Would like to thank Sander for spotting and suggesting this. > pvspinlock benefit on KVM link: https://lkml.org/lkml/2013/8/6/178 > > Attilio's tests on native kernel impact: > http://blog.xen.org/index.php/2012/05/11/benchmarking-the-new-pv-ticketlock-implementation/ > > arch/x86/Kconfig | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index f67e839..4ba9d32 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -638,10 +638,10 @@ config PARAVIRT_SPINLOCKS > spinlock implementation with something virtualization-friendly > (for example, block the virtual CPU rather than spinning). > > - Unfortunately the downside is an up to 5% performance hit on > - native kernels, with various workloads. > + It has minimal impact on native kernels and gives nice performance > + benefit for paravirtualized KVM / Xen kernels. > > - If you are unsure how to answer this question, answer N. > + If you are unsure how to answer this question, answer Y. > > source "arch/x86/xen/Kconfig" > > -- > 1.7.11.7 >