From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753988AbbAGQ7R (ORCPT ); Wed, 7 Jan 2015 11:59:17 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:47007 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753775AbbAGQ7Q (ORCPT ); Wed, 7 Jan 2015 11:59:16 -0500 Message-ID: <54AD65D4.9070101@oracle.com> Date: Wed, 07 Jan 2015 11:59:00 -0500 From: Boris Ostrovsky User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Imre Palik , xen-devel@lists.xenproject.org CC: Konrad Rzeszutek Wilk , David Vrabel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, "Palik, Imre" , Anthony Liguori Subject: Re: [PATCH RFC] xen-time: decreasing the rating of the xen clocksource below that of the tsc clocksource for dom0's References: <1420647398-20207-1-git-send-email-imrep.amz@gmail.com> In-Reply-To: <1420647398-20207-1-git-send-email-imrep.amz@gmail.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/07/2015 11:16 AM, Imre Palik wrote: > From: "Palik, Imre" > > In Dom0's the use of the TSC clocksource (whenever it is stable enough to > be used) instead of the Xen clocksource should not cause any issues, as > Dom0 VMs never live-migrated. The TSC clocksource is somewhat more > efficient than the Xen paravirtualised clocksource, thus it should have > higher rating. > > Cc: Anthony Liguori > Signed-off-by: Imre Palik > --- > arch/x86/xen/time.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c > index f473d26..c768726 100644 > --- a/arch/x86/xen/time.c > +++ b/arch/x86/xen/time.c > @@ -487,6 +487,10 @@ static void __init xen_time_init(void) > int cpu = smp_processor_id(); > struct timespec tp; > > + /* As Dom0 is never moved, no penalty on using TSC there */ > + if (xen_initial_domain()) > + xen_clocksource.rating = 275; Should this only be limited to dom0? Can we do this for guests running with TSC_MODE_NEVER_EMULATE as well? We also have disable_migrate flag for guests (but it doesn't appear to be accessible to a guest kernel). -boris > + > clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC); > > if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {