From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH RFC V6 0/11] Paravirtualized ticketlocks Date: Thu, 05 Apr 2012 12:01:15 +0300 Message-ID: <4F7D5F5B.2020209@redhat.com> References: <20120321102041.473.61069.sendpatchset@codeblue.in.ibm.com> <4F707C5F.1000905@redhat.com> <4F716E31.3000803@linux.vnet.ibm.com> <4F73568D.7000703@linux.vnet.ibm.com> <4F743247.5080407@redhat.com> <4F74A405.2040609@linux.vnet.ibm.com> <4F7585EE.7060203@linux.vnet.ibm.com> <4F7855A1.80107@redhat.com> <4F785CC9.7070204@linux.vnet.ibm.com> <4F785DCF.7020809@redhat.com> <4F7976B6.5050000@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: KVM , Alan Meadows , Peter Zijlstra , Stefano Stabellini , the arch/x86 maintainers , LKML , Konrad Rzeszutek Wilk , Andi Kleen , Srivatsa Vaddagiri , Jeremy Fitzhardinge , "H. Peter Anvin" , Attilio Rao , Ingo Molnar , Virtualization , Linus Torvalds , Xen Devel , Stephan Diestelhorst To: Raghavendra K T Return-path: In-Reply-To: <4F7976B6.5050000@linux.vnet.ibm.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 List-Id: kvm.vger.kernel.org On 04/02/2012 12:51 PM, Raghavendra K T wrote: > On 04/01/2012 07:23 PM, Avi Kivity wrote: > > On 04/01/2012 04:48 PM, Raghavendra K T wrote: > >>>> I have patch something like below in mind to try: > >>>> > >>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > >>>> index d3b98b1..5127668 100644 > >>>> --- a/virt/kvm/kvm_main.c > >>>> +++ b/virt/kvm/kvm_main.c > >>>> @@ -1608,15 +1608,18 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) > >>>> * else and called schedule in __vcpu_run. Hopefully that > >>>> * VCPU is holding the lock that we need and will release it. > >>>> * We approximate round-robin by starting at the last boosted > >>>> VCPU. > >>>> + * Priority is given to vcpu that are unhalted. > >>>> */ > >>>> - for (pass = 0; pass< 2&& !yielded; pass++) { > >>>> + for (pass = 0; pass< 3&& !yielded; pass++) { > >>>> kvm_for_each_vcpu(i, vcpu, kvm) { > >>>> struct task_struct *task = NULL; > >>>> struct pid *pid; > >>>> - if (!pass&& i< last_boosted_vcpu) { > >>>> + if (!pass&& !vcpu->pv_unhalted) > >>>> + continue; > >>>> + else if (pass == 1&& i< last_boosted_vcpu) { > >>>> i = last_boosted_vcpu; > >>>> continue; > >>>> - } else if (pass&& i> last_boosted_vcpu) > >>>> + } else if (pass == 2&& i> last_boosted_vcpu) > >>>> break; > >>>> if (vcpu == me) > >>>> continue; > >>>> > >>> > >>> Actually I think this is unneeded. The loops tries to find vcpus > that > >>> are runnable but not running (vcpu_active(vcpu->wq)), and halted > vcpus > >>> don't match this condition. > >>> > > Oh! I think I misinterpreted your statement. hmm I got it. you told to > remove if (vcpu == me) condition. No, the entire patch is unneeded. My original comment was: > from the PLE handler, don't wake up a vcpu that is sleeping because it is waiting for a kick But the PLE handler never wakes up sleeping vcpus anyway. There's still a conflict with PLE in that it may trigger during the spin phase and send a random yield_to() somewhere. Maybe it's sufficient to tune the PLE timeout to be longer than the spinlock timeout. -- error compiling committee.c: too many arguments to function