From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:59221) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ehfKq-0005DL-Nx for qemu-devel@nongnu.org; Fri, 02 Feb 2018 12:42:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ehfJm-0005oE-Iu for qemu-devel@nongnu.org; Fri, 02 Feb 2018 12:41:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:5771) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ehfJl-0005l7-Qj for qemu-devel@nongnu.org; Fri, 02 Feb 2018 12:40:06 -0500 Date: Fri, 2 Feb 2018 15:38:46 -0200 From: Eduardo Habkost Message-ID: <20180202173846.GN26425@localhost.localdomain> References: <20180201125441.2f5b4fdd@redhat.com> <20180201201514.GB660@flask> <20180201202649.GG26425@localhost.localdomain> <20180202141554.GH26425@localhost.localdomain> <20180202141938.GJ15403@redhat.com> <20180202092159.48d9bd4c@redhat.com> <20180202145014.GI26425@localhost.localdomain> <20180202172359.GA2591@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20180202172359.GA2591@work-vm> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC] kvm: x86: export vCPU halted state to sysfs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Luiz Capitulino , Peter Krempa , kvm@vger.kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= , libvir-list@redhat.com, Markus Armbruster , qemu-devel@nongnu.org, Viktor Mihajlovski , Christian Borntraeger , John Ferlan , pbonzini@redhat.com On Fri, Feb 02, 2018 at 05:23:59PM +0000, Dr. David Alan Gilbert wrote: > * Eduardo Habkost (ehabkost@redhat.com) wrote: > > (CCing qemu-devel) > >=20 > > On Fri, Feb 02, 2018 at 09:21:59AM -0500, Luiz Capitulino wrote: > > > On Fri, 2 Feb 2018 14:19:38 +0000 > > > Daniel P. Berrang=E9 wrote: > > > > On Fri, Feb 02, 2018 at 12:15:54PM -0200, Eduardo Habkost wrote: > > [...] > > > > > It would be also interesting to update QEMU QMP documentation t= o > > > > > clarify the arch-specific semantics of "halted". =20 > > > >=20 > > > > Any also especially clarify the awful performance implications of= running > > > > this particular query command. In general I would not expect quer= y-xxx > > > > monitor commands to interrupt all vcpus, so we should clearly war= n about > > > > this ! > > >=20 > > > Or deprecate it... > >=20 > > We could deprecate the expensive fields on query-cpus, and move > > them to a more expensive query-cpu-state command. I believe most > > users of query-cpus are only interested in qom_path, thread_id, > > and topology info. >=20 > Would that data be available without the bql? I ask because if it is > then a small advantage to having a separate command is that the command > could be marked OOB with Peter's new series and never take the lock. We would need a mechanism to safely walk the CPU list without the BQL, so I wouldn't bother trying to make a OOB-capable version of query-cpus unless really necessary. --=20 Eduardo