From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH RFC V6 0/11] Paravirtualized ticketlocks Date: Sun, 01 Apr 2012 19:18:57 +0530 Message-ID: <4F785CC9.7070204@linux.vnet.ibm.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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F7855A1.80107@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: Avi Kivity 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 List-Id: virtualization@lists.linuxfoundation.org On 04/01/2012 06:48 PM, Avi Kivity wrote: > On 03/30/2012 01:07 PM, Raghavendra K T wrote: >> On 03/29/2012 11:33 PM, Raghavendra K T wrote: >>> On 03/29/2012 03:28 PM, Avi Kivity wrote: >>>> On 03/28/2012 08:21 PM, Raghavendra K T wrote: >> >>> I really like below ideas. Thanks for that!. >>> >>>> - from the PLE handler, don't wake up a vcpu that is sleeping >>>> because it >>>> is waiting for a kick >>> >>> How about, adding another pass in the beginning of kvm_vcpu_on_spin() >>> to check if any vcpu is already kicked. This would almost result in >>> yield_to(kicked_vcpu). IMO this is also worth trying. >>> >>> will try above ideas soon. >>> >> >> 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. > I almost agree. But at corner of my thought, Suppose there are 8 vcpus runnable out of which 4 of them are kicked but not running, making yield_to those 4 vcpus would result in better lock progress. no? I still have little problem getting PLE setup, here (instead rebasing patches). Once I get PLE to get that running, and numbers prove no improvement, I will drop this idea.