From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: [patch 18/18] KVM: x86: update pvclock area conditionally, on cpu migration Date: Mon, 19 Nov 2012 19:58:16 -0200 Message-ID: <20121119215959.499058001@redhat.com> References: <20121119215758.686768790@redhat.com> Cc: johnstul@us.ibm.com, jeremy@goop.org, glommer@parallels.com, Marcelo Tosatti To: mingo@kernel.org, kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:27213 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752785Ab2KSV6c (ORCPT ); Mon, 19 Nov 2012 16:58:32 -0500 Content-Disposition: inline; filename=18-do-not-writeclock-on-cpu-migration Sender: kvm-owner@vger.kernel.org List-ID: As requested by Glauber, do not update kvmclock area on vcpu->pcpu migration, in case the host has stable TSC. This is to reduce cacheline bouncing. Signed-off-by: Marcelo Tosatti Index: vsyscall/arch/x86/kvm/x86.c =================================================================== --- vsyscall.orig/arch/x86/kvm/x86.c +++ vsyscall/arch/x86/kvm/x86.c @@ -2615,7 +2615,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu kvm_x86_ops->write_tsc_offset(vcpu, offset); vcpu->arch.tsc_catchup = 1; } - kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); + /* + * On a host with synchronized TSC, there is no need to update + * kvmclock on vcpu->cpu migration + */ + if (!vcpu->kvm->arch.use_master_clock || vcpu->cpu == -1) + kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); if (vcpu->cpu != cpu) kvm_migrate_timers(vcpu); vcpu->cpu = cpu;