lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 24 Sep 2012 18:06:54 +0200 From: Avi Kivity <avi@...hat.com> To: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>, Peter Zijlstra <peterz@...radead.org> CC: Rik van Riel <riel@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>, Srikar <srikar@...ux.vnet.ibm.com>, "Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>, KVM <kvm@...r.kernel.org>, Jiannan Ouyang <ouyang@...pitt.edu>, chegu vinod <chegu_vinod@...com>, "Andrew M. Theurer" <habanero@...ux.vnet.ibm.com>, LKML <linux-kernel@...r.kernel.org>, Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>, Gleb Natapov <gleb@...hat.com> Subject: Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLE handler On 09/24/2012 05:41 PM, Avi Kivity wrote: > >> >> case 2) >> rq1 : vcpu1->wait(lockA) (spinning) >> rq2 : vcpu3 (running) , vcpu2->holding(lockA) [scheduled out] >> >> I agree that checking rq1 length is not proper in this case, and as you >> rightly pointed out, we are in trouble here. >> nr_running()/num_online_cpus() would give more accurate picture here, >> but it seemed costly. May be load balancer save us a bit here in not >> running to such sort of cases. ( I agree load balancer is far too >> complex). > > In theory preempt notifier can tell us whether a vcpu is preempted or > not (except for exits to userspace), so we can keep track of whether > it's we're overcommitted in kvm itself. It also avoids false positives > from other guests and/or processes being overcommitted while our vm is fine. It also allows us to cheaply skip running vcpus. We would probably need a ->sched_exit() preempt notifier to make this work. Peter, I know how much you love those, would it be acceptable? We'd still need yield_to() but the pressure on it might be reduced. -- error compiling committee.c: too many arguments to function -- 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/
Powered by blists - more mailing lists