From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47334) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emL10-0003bg-Bp for qemu-devel@nongnu.org; Thu, 15 Feb 2018 10:00:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1emL0w-0007pg-Dl for qemu-devel@nongnu.org; Thu, 15 Feb 2018 10:00:02 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:60986) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1emL0w-0007ou-5U for qemu-devel@nongnu.org; Thu, 15 Feb 2018 09:59:58 -0500 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w1FEtjM7130299 for ; Thu, 15 Feb 2018 09:59:56 -0500 Received: from e06smtp13.uk.ibm.com (e06smtp13.uk.ibm.com [195.75.94.109]) by mx0a-001b2d01.pphosted.com with ESMTP id 2g5avucfga-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 15 Feb 2018 09:59:54 -0500 Received: from localhost by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 15 Feb 2018 14:59:52 -0000 References: <1518690027-31318-1-git-send-email-mihajlov@linux.vnet.ibm.com> <1518690027-31318-3-git-send-email-mihajlov@linux.vnet.ibm.com> <3b41b0f0-09cf-9e43-bfa4-617335d76584@redhat.com> <50053a43-4905-9609-9be3-8418f1978465@linux.vnet.ibm.com> From: Viktor Mihajlovski Date: Thu, 15 Feb 2018 15:59:47 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Message-Id: <55d9d665-df3d-80d1-2aab-a914493febc8@linux.vnet.ibm.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCHv3 2/4] qmp: add query-cpus-fast List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , qemu-devel@nongnu.org Cc: agraf@suse.de, ehabkost@redhat.com, armbru@redhat.com, cohuck@redhat.com, david@redhat.com, dgilbert@redhat.com, borntraeger@de.ibm.com, qemu-s390x@nongnu.org, pbonzini@redhat.com, rth@twiddle.net On 15.02.2018 15:53, Eric Blake wrote: > On 02/15/2018 08:40 AM, Viktor Mihajlovski wrote: >> On 15.02.2018 15:19, Eric Blake wrote: >>> On 02/15/2018 04:20 AM, Viktor Mihajlovski wrote: >>>> From: Luiz Capitulino >>>> >>>> The query-cpus command has an extremely serious side effect: >>>> it always interrupts all running vCPUs so that they can run >>>> ioctl calls. This can cause a huge performance degradation for >>>> some workloads. And most of the information retrieved by the >>>> ioctl calls are not even used by query-cpus. >>>> >>>> This commit introduces a replacement for query-cpus called >=20 >>> You know, we have no back-compat guarantees on HMP.=C2=A0 We could ma= ke 'info >>> cpu' just ALWAYS call query-cpus-fast, with no HMP counterpart for th= e >>> slower query-cpus, and without needing a deprecation period.=C2=A0 Bu= t I'll >>> leave that up to David if that makes more sense. >> Ditching info cpus_fast would make me happy as well, because it would >> cause less headache on the libvirt side of things. >=20 > Why is libvirt using HMP in the first place?=C2=A0 Libvirt should alway= s be > using the QMP command, when one exists. > Which it does, but there's still a lot of fallback code including HMP "info cpus". In real life this should of course never be used, because the QMP is always there. --=20 Regards, Viktor Mihajlovski