From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks Date: Wed, 10 Jul 2013 17:20:40 +0530 Message-ID: <51DD4A90.7040507@linux.vnet.ibm.com> References: <1372171802.3804.30.camel@oc2024037011.ibm.com> <51CAAA26.4090204@linux.vnet.ibm.com> <20130626113744.GA6300@hawk.usersys.redhat.com> <20130626125240.GY18508@redhat.com> <51CAEF45.3010203@linux.vnet.ibm.com> <20130626161130.GB18152@redhat.com> <51CB2AD9.5060508@linux.vnet.ibm.com> <51DBD3C2.2040807@linux.vnet.ibm.com> <20130710103325.GP24941@redhat.com> <51DD445C.5070801@linux.vnet.ibm.com> <20130710114150.GU24941@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130710114150.GU24941@redhat.com> 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: Gleb Natapov Cc: jeremy@goop.org, gregkh@suse.de, kvm@vger.kernel.org, linux-doc@vger.kernel.org, peterz@infradead.org, riel@redhat.com, virtualization@lists.linux-foundation.org, andi@firstfloor.org, hpa@zytor.com, stefano.stabellini@eu.citrix.com, xen-devel@lists.xensource.com, x86@kernel.org, mingo@redhat.com, habanero@linux.vnet.ibm.com, Andrew Jones , konrad.wilk@oracle.com, ouyang@cs.pitt.edu, avi.kivity@gmail.com, tglx@linutronix.de, chegu_vinod@hp.com, linux-kernel@vger.kernel.org, srivatsa.vaddagiri@gmail.com, attilio.rao@citrix.com, pbonzini@redhat.com, torvalds@linux-foundation.org List-Id: xen-devel@lists.xenproject.org On 07/10/2013 05:11 PM, Gleb Natapov wrote: > On Wed, Jul 10, 2013 at 04:54:12PM +0530, Raghavendra K T wrote: >>>> Ingo, Gleb, >>>> >>>> From the results perspective, Andrew Theurer, Vinod's test results are >>>> pro-pvspinlock. >>>> Could you please help me to know what will make it a mergeable >>>> candidate?. >>>> >>> I need to spend more time reviewing it :) The problem with PV interfaces >>> is that they are easy to add but hard to get rid of if better solution >>> (HW or otherwise) appears. >> >> Infact Avi had acked the whole V8 series, but delayed for seeing how >> PLE improvement would affect it. >> > I see that Ingo was happy with it too. > >> The only addition from that series has been >> 1. tuning the SPIN_THRESHOLD to 32k (from 2k) >> and >> 2. the halt handler now calls vcpu_on_spin to take the advantage of >> PLE improvements. (this can also go as an independent patch into >> kvm) >> >> The rationale for making SPIN_THERSHOLD 32k needs big explanation. >> Before PLE improvements, as you know, >> kvm undercommit scenario was very worse in ple enabled cases. >> (compared to ple disabled cases). >> pvspinlock patches behaved equally bad in undercommit. Both had >> similar reason so at the end there was no degradation w.r.t base. >> >> The reason for bad performance in PLE case was unneeded vcpu >> iteration in ple handler resulting in high yield_to calls and double >> run queue locks. >> With pvspinlock applied, same villain role was played by excessive >> halt exits. >> >> But after ple handler improved, we needed to throttle unnecessary halts >> in undercommit for pvspinlock to be on par with 1x result. >> > Make sense. I will review it ASAP. BTW the latest version is V10 right? > Yes. Thank you.