From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41971) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eXUkK-0002xj-Oc for qemu-devel@nongnu.org; Fri, 05 Jan 2018 11:21:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eXUkH-0000LO-Hh for qemu-devel@nongnu.org; Fri, 05 Jan 2018 11:21:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38366) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eXUkH-0000K8-7F for qemu-devel@nongnu.org; Fri, 05 Jan 2018 11:21:25 -0500 References: <1509369390-8285-1-git-send-email-a.perevalov@samsung.com> <1509369390-8285-7-git-send-email-a.perevalov@samsung.com> <64a69d83-c575-5bd2-66f4-5b88172418a2@redhat.com> <83b57241-63b2-c4c2-8b37-9fc288de53f6@samsung.com> From: Eric Blake Message-ID: Date: Fri, 5 Jan 2018 10:21:19 -0600 MIME-Version: 1.0 In-Reply-To: <83b57241-63b2-c4c2-8b37-9fc288de53f6@samsung.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="5iTtsOytBmVAHFrN2BOoOYyaCEXgRXN7V" Subject: Re: [Qemu-devel] [PATCH v12 6/6] migration: add postcopy total blocktime into query-migrate List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Perevalov , qemu-devel@nongnu.org Cc: heetae82.ahn@samsung.com, quintela@redhat.com, dgilbert@redhat.com, peterx@redhat.com, i.maximets@samsung.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --5iTtsOytBmVAHFrN2BOoOYyaCEXgRXN7V From: Eric Blake To: Alexey Perevalov , qemu-devel@nongnu.org Cc: heetae82.ahn@samsung.com, quintela@redhat.com, dgilbert@redhat.com, peterx@redhat.com, i.maximets@samsung.com Message-ID: Subject: Re: [Qemu-devel] [PATCH v12 6/6] migration: add postcopy total blocktime into query-migrate References: <1509369390-8285-1-git-send-email-a.perevalov@samsung.com> <1509369390-8285-7-git-send-email-a.perevalov@samsung.com> <64a69d83-c575-5bd2-66f4-5b88172418a2@redhat.com> <83b57241-63b2-c4c2-8b37-9fc288de53f6@samsung.com> In-Reply-To: <83b57241-63b2-c4c2-8b37-9fc288de53f6@samsung.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 01/05/2018 06:15 AM, Alexey Perevalov wrote: > On 01/03/2018 12:26 AM, Eric Blake wrote: >> On 10/30/2017 08:16 AM, Alexey Perevalov wrote: >>> Postcopy total blocktime is available on destination side only. >>> But query-migrate was possible only for source. This patch >>> adds ability to call query-migrate on destination. >>> To be able to see postcopy blocktime, need to request postcopy-blockt= ime >>> capability. >> Why not display the stats unconditionally when they are available, >> instead of having to set a capability knob to request them? > That knob necessary to avoid regression if this information > is not necessary, we decided during so long discussion in previous > version of the patch set - it's not necessary always. > But if user requested blocktime and host can't calculate it, > e.g. due to appropriate feature isn't supported in host kernel, > yes, the value will be 0. >=20 >>> =C2=A0 # >>> +# @postcopy-blocktime: total time when all vCPU were blocked during >>> postcopy >>> +#=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 live m= igration (Since 2.11) >> 2.12 now. >> >> Should this mention the capability knob needed to enable this stat (or= >> else get rid of the capability knob and always expose this when >> possible)? >> Okay, so you've explained that the knob is necessary because there is a noticeable performance difference for users that don't care about the statistic; in which case, we DO need a followup patch (or a v2 of Juan's pull request) that documents that this statistic is useless unless you set the migration capability. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org --5iTtsOytBmVAHFrN2BOoOYyaCEXgRXN7V Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAlpPpf8ACgkQp6FrSiUn Q2oeuQgAhBpc0LOfKjM1be/GLyLGIAFiIrcwxYfiz7GOl+lZ/rlwvYQTkLijh8QG 8Bafcn19a4noOv2nEmSyEHX/eagttn427L2fyp7oFpWk7t5m3VP+FicXcHr6ZapS s5kWuXMcrnHKjosPKRYso9froRdCK2vpdRHiCTz6RuUNDpKA2j5G0P/4zZgJVAAt csqCWtlJ+dEO6KUdjwh0SsxrCy06lkfqTRVm1khAi3wxrBFLzEkUkLxYgA2etMX/ OSRgzLnpUDlv+PeMQGoXNlxk8eq/h6CGm95j9G5pQJjCLvvmbCQzn6GS810RTKES t1F5ts+wmnbn6TUB61x3UiYCHZ1iTw== =L0Ou -----END PGP SIGNATURE----- --5iTtsOytBmVAHFrN2BOoOYyaCEXgRXN7V--