From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] [RESEND] KVM:VMX: Add support for Pause-Loop Exiting Date: Sun, 27 Sep 2009 15:47:55 +0200 Message-ID: <4ABF6D0B.8080603@redhat.com> References: <4ABA2AD7.6080008@intel.com> <4ABA2C22.7020000@redhat.com> <20090925204339.GA29634@8bytes.org> <4ABF22D9.3040308@redhat.com> <20090927134650.GC29634@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "Zhai, Edwin" , Ingo Molnar , "kvm@vger.kernel.org" To: Joerg Roedel Return-path: Received: from mx1.redhat.com ([209.132.183.28]:27772 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752711AbZI0NsJ (ORCPT ); Sun, 27 Sep 2009 09:48:09 -0400 In-Reply-To: <20090927134650.GC29634@8bytes.org> Sender: kvm-owner@vger.kernel.org List-ID: On 09/27/2009 03:46 PM, Joerg Roedel wrote: > >> We can't find exactly which vcpu, but we can: >> >> - rule out threads that are not vcpus for this guest >> - rule out threads that are already running >> >> A major problem with sleep() is that it effectively reduces the vm >> priority relative to guests that don't have spinlock contention. By >> selecting a random nonrunnable vcpu belonging to this guest, we at least >> preserve the guest's timeslice. >> > Ok, that makes sense. But before trying that we should probably try to > call just yield() instead of schedule()? I remember someone from our > team here at AMD did this for Xen a while ago and already had pretty > good results with that. Xen has a completly other scheduler but maybe > its worth trying? > yield() is a no-op in CFS. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.