From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44651) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emKud-0005Pq-B4 for qemu-devel@nongnu.org; Thu, 15 Feb 2018 09:53:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1emKuc-0003wv-Gp for qemu-devel@nongnu.org; Thu, 15 Feb 2018 09:53:27 -0500 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: Eric Blake Message-ID: Date: Thu, 15 Feb 2018 08:53:23 -0600 MIME-Version: 1.0 In-Reply-To: <50053a43-4905-9609-9be3-8418f1978465@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US 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: Viktor Mihajlovski , 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 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 >> You know, we have no back-compat guarantees on HMP.=C2=A0 We could mak= e 'info >> cpu' just ALWAYS call query-cpus-fast, with no HMP counterpart for the >> slower query-cpus, and without needing a deprecation period.=C2=A0 But= 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. Why is libvirt using HMP in the first place? Libvirt should always be=20 using the QMP command, when one exists. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org