From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests Date: Tue, 17 Jan 2012 22:57:58 +0530 Message-ID: <4F15AF9E.9000907@linux.vnet.ibm.com> References: <20120114182501.8604.68416.sendpatchset@oc5400248562.ibm.com> <3EC1B881-0724-49E3-B892-F40BEB07D15D@suse.de> <20120116142014.GA10155@linux.vnet.ibm.com> <4F146EA5.3010106@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Alexander Graf Cc: Jeremy Fitzhardinge , Greg Kroah-Hartman , linux-doc@vger.kernel.org, Peter Zijlstra , Jan Kiszka , Srivatsa Vaddagiri , Paul Mackerras , "H. Peter Anvin" , Stefano Stabellini , Xen , Dave Jiang , KVM , Glauber Costa , X86 , Ingo Molnar , Avi Kivity , Rik van Riel , Konrad Rzeszutek Wilk , Sasha Levin , Sedat Dilek , Thomas Gleixner , Virtualization , LKML , Dave Hansen List-Id: virtualization@lists.linuxfoundation.org On 01/17/2012 12:12 AM, Alexander Graf wrote: > > On 16.01.2012, at 19:38, Raghavendra K T wrote: > >> On 01/16/2012 07:53 PM, Alexander Graf wrote: >>> >>> On 16.01.2012, at 15:20, Srivatsa Vaddagiri wrote: >>> >>>> * Alexander Graf [2012-01-16 04:57:45]: >>>> >>>>> Speaking of which - have you benchmarked performance degradation of pv ticket locks on bare metal? >>>> >>>> You mean, run kernel on bare metal with CONFIG_PARAVIRT_SPINLOCKS >>>> enabled and compare how it performs with CONFIG_PARAVIRT_SPINLOCKS disabled for >>>> some workload(s)? >>> >>> Yup >>> >>>> >>>> In some sense, the 1x overcommitcase results posted does measure the overhead >>>> of (pv-)spinlocks no? We don't see any overhead in that case for atleast >>>> kernbench .. >>>> >>>>> Result for Non PLE machine : >>>>> ============================ >>>> >>>> [snip] >>>> >>>>> Kernbench: >>>>> BASE BASE+patch >>> >>> What is BASE really? Is BASE already with the PV spinlocks enabled? I'm having a hard time understanding which tree you're working against, since the prerequisites aren't upstream yet. >>> >>> >>> Alex >> >> Sorry for confusion, I think I was little imprecise on the BASE. >> >> The BASE is pre 3.2.0 + Jeremy's following patches: >> xadd (https://lkml.org/lkml/2011/10/4/328) >> x86/ticketlocklock (https://lkml.org/lkml/2011/10/12/496). >> So this would have ticketlock cleanups from Jeremy and >> CONFIG_PARAVIRT_SPINLOCKS=y >> >> BASE+patch = pre 3.2.0 + Jeremy's above patches + above V5 PV spinlock >> series and CONFIG_PARAVIRT_SPINLOCKS=y >> >> In both the cases CONFIG_PARAVIRT_SPINLOCKS=y. >> >> So let, >> A. pre-3.2.0 with CONFIG_PARAVIRT_SPINLOCKS = n >> B. pre-3.2.0 + Jeremy's above patches with CONFIG_PARAVIRT_SPINLOCKS = n >> C. pre-3.2.0 + Jeremy's above patches with CONFIG_PARAVIRT_SPINLOCKS = y >> D. pre-3.2.0 + Jeremy's above patches + V5 patches with CONFIG_PARAVIRT_SPINLOCKS = n >> E. pre-3.2.0 + Jeremy's above patches + V5 patches with CONFIG_PARAVIRT_SPINLOCKS = y >> >> is it performance of A vs E ? (currently C vs E) > > Since D and E only matter with KVM in use, yes, I'm mostly interested in A, B and C :). > > > Alex > > setup : Native: IBM xSeries with Intel(R) Xeon(R) x5570 2.93GHz CPU with 8 core , 64GB RAM, (16 cpu online) Guest : Single guest with 8 VCPU 4GB Ram. benchmark : kernbench -f -H -M -o 20 Here is the result : Native Run ============ case A case B %improvement case C %improvement 56.1917 (2.57125) 56.035 (2.02439) 0.278867 56.27 (2.40401) -0.139344 Guest Run ============ case A case B %improvement case C %improvement 166.999 (15.7613) 161.876 (14.4874) 3.06768 161.24 (12.6497) 3.44852 We do not see much overhead in native run with CONFIG_PARAVIRT_SPINLOCKS = y