Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752527AbaLSXe6 (ORCPT ); Fri, 19 Dec 2014 18:34:58 -0500 Received: from mga14.intel.com ([192.55.52.115]:5215 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751365AbaLSXe5 convert rfc822-to-8bit (ORCPT ); Fri, 19 Dec 2014 18:34:57 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,609,1413270000"; d="scan'208";a="640529557" From: "Wu, Feng" To: Paolo Bonzini , "Zhang, Yang Z" , KVM list CC: "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , "Wu, Feng" Subject: RE: [v3 25/26] KVM: Suppress posted-interrupt when 'SN' is set Thread-Topic: [v3 25/26] KVM: Suppress posted-interrupt when 'SN' is set Thread-Index: AQHQG4NsmEtuDH0qPk6Pb+YapmEtyZyXkY0Q Date: Fri, 19 Dec 2014 23:34:51 +0000 Message-ID: References: <1418397300-10870-1-git-send-email-feng.wu@intel.com> <1418397300-10870-26-git-send-email-feng.wu@intel.com> <5491C0A2.7040503@redhat.com> <5492926E.8070207@redhat.com> <54941365.60604@redhat.com> In-Reply-To: <54941365.60604@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo > Bonzini > Sent: Friday, December 19, 2014 8:01 PM > To: Zhang, Yang Z; Wu, Feng; Paolo Bonzini; KVM list > Cc: iommu@lists.linux-foundation.org; linux-kernel@vger.kernel.org > Subject: Re: [v3 25/26] KVM: Suppress posted-interrupt when 'SN' is set > > > > On 19/12/2014 06:25, Zhang, Yang Z wrote: > > I see your point. But from performance point, if we can schedule the > > vCPU to another PCPU to handle the interrupt, it would helpful. But I > > remember current KVM will not schedule the vCPU in run queue (even > > though it got preempted) to another pCPU to run(Am I right?). So it > > may hard to do it. > > Yes. If the vCPU is in the run queue, it means it exhausted its > quantum. As Feng said, the scheduler can decide to migrate it to > another pCPU, or it can decide to leave it runnable but not start it. > KVM doesn't try to force the scheduler one way or the other. > > If the vCPU is I/O bound, it will not exhaust its quantum and will not > be preempted. It will block, and the wakeup vector will restart it. > > I don't think urgent notifications are interesting. If you want to do > real time work, pin the vCPU to a physical CPU, and isolate the pCPU > with isolcpus. Then the vCPU will always be running. > > Paolo I agree, thanks Paolo! Thanks, Feng -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/