From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48473) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1elKpN-0002QI-Ap for qemu-devel@nongnu.org; Mon, 12 Feb 2018 15:35:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1elKpI-0005mS-Cf for qemu-devel@nongnu.org; Mon, 12 Feb 2018 15:35:53 -0500 References: <1518437672-7724-1-git-send-email-mihajlov@linux.vnet.ibm.com> <1518437672-7724-3-git-send-email-mihajlov@linux.vnet.ibm.com> From: David Hildenbrand Message-ID: Date: Mon, 12 Feb 2018 21:35:28 +0100 MIME-Version: 1.0 In-Reply-To: <1518437672-7724-3-git-send-email-mihajlov@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/3] 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: qemu-s390x@nongnu.org, lcapitulino@redhat.com, ehabkost@redhat.com, pbonzini@redhat.com, crosthwaite.peter@gmail.com, dgilbert@redhat.com, rth@twiddle.net, cohuck@redhat.com, borntraeger@de.ibm.com, agraf@suse.de, eblake@redhat.com, armbru@redhat.com, berrange@redhat.com On 12.02.2018 13:14, 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 > query-cpus-fast, which has the following features: > > o Never interrupt vCPUs threads. query-cpus-fast only returns > vCPU information maintained by QEMU itself, which should be > sufficient for most management software needs > > o Make "halted" field optional: we only return it if the > halted state is maintained by QEMU. But this also gives > the option of dropping the field in the future (see below) > If I'm not wrong, this comment is superseded by ... > o Drop irrelevant fields such as "current", "pc" and "arch" > > o Drop field "halted" since it can't be provided fast reliably > and is too volatile on most architectures to be really useful > this comment :) > o Rename some fields for better clarification & proper naming > standard> > Signed-off-by: Luiz Capitulino > Signed-off-by: Viktor Mihajlovski Wondering if we could tweak the old interface with a simple flag "fast = true". -- Thanks, David / dhildenb