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Date: Wed, 10 Jul 2013 17:20:40 +0530 From: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> To: Gleb Natapov <gleb@...hat.com> CC: Andrew Jones <drjones@...hat.com>, mingo@...hat.com, ouyang@...pitt.edu, habanero@...ux.vnet.ibm.com, jeremy@...p.org, x86@...nel.org, konrad.wilk@...cle.com, hpa@...or.com, pbonzini@...hat.com, linux-doc@...r.kernel.org, xen-devel@...ts.xensource.com, peterz@...radead.org, mtosatti@...hat.com, stefano.stabellini@...citrix.com, andi@...stfloor.org, attilio.rao@...rix.com, gregkh@...e.de, agraf@...e.de, chegu_vinod@...com, torvalds@...ux-foundation.org, avi.kivity@...il.com, tglx@...utronix.de, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, riel@...hat.com, virtualization@...ts.linux-foundation.org, srivatsa.vaddagiri@...il.com Subject: Re: [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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