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09:39:00 +0100 Date: Mon, 24 Nov 2025 09:38:57 +0100 From: Lukas Straub To: Zhang Chen Cc: "Zhijian Li (Fujitsu)" , Peter Xu , "zhanghailiang@xfusion.com" , "farosas@suse.de" , "qemu-devel@nongnu.org" Subject: Re: [PATCH] migration: Fix transition to COLO state from precopy Message-ID: <20251124093857.1fa22ded@penguin> In-Reply-To: References: <20251104013606.1937764-1-lizhijian@fujitsu.com> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="Sig_/kb=8f9B2PaZ=J7kJiCHBNsd"; protocol="application/pgp-signature"; micalg=pgp-sha512 X-Provags-ID: V03:K1:ajd9gOPG4p9RDhVE4BTLYQLjCqda2oNSHLtT3ZBitklKz6Awz5u Uvd0WnWtwOWyijLis3w2bgnRSzg0kYQtMAFvPacya8wxU476XKlkWEV/q3L08KMuCMDtUu9 rDaPa1JpPmSfqIUgZTm9mXOgCtNnbzvVKDInlVitJcAzwZFa5VlkQvJCWz11+1iPSxCiZcd wvj3IIkCLY+ovgvq5Gt9A== UI-OutboundReport: notjunk:1;M01:P0:KXgd9K0oRJs=;1gN7UE2LKkh12DLpi7Nh8EWUVFc YqZMQUGG0K4+n9CLhjrb2ZlRDNBqRG90pxPmVSbVjZLCeydjatHsF6OHG+9TC3xK/YzRu8CBS 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action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --Sig_/kb=8f9B2PaZ=J7kJiCHBNsd Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Thu, 6 Nov 2025 11:21:56 +0800 Zhang Chen wrote: > On Thu, Nov 6, 2025 at 9:10=E2=80=AFAM Zhijian Li (Fujitsu) > wrote: > > > > > > > > On 06/11/2025 04:58, Peter Xu wrote: =20 > > > On Tue, Nov 04, 2025 at 09:36:06AM +0800, Li Zhijian wrote: =20 > > >> Commit 4881411136 ("migration: Always set DEVICE state") set a new D= EVICE > > >> state before completed during migration, which broke the original tr= ansition > > >> to COLO. The migration flow for precopy has changed to: > > >> active -> pre-switchover -> device -> completed. > > >> > > >> This patch updates the transition state to ensure that the Pre-COLO > > >> state corresponds to DEVICE state correctly. > > >> > > >> Fixes: 4881411136 ("migration: Always set DEVICE state") > > >> Signed-off-by: Li Zhijian > > >> --- > > >> [...] > > > > > > Thanks a lot for fixing it, Zhijian. It means I broke COLO already f= or > > > 10.0/10.1.. > > > > > > Hailiang/Chen, do you still know anyone who is using COLO, especially= in > > > enterprise? I don't expect any individual using it.. It definitely > > > complicates migration logics all over the places. Fabiano and I disc= ussed > > > a few times on removing legacy code and COLO was always in the list. > > > > > > We used to discuss RDMA obsoletion too, that's when Huawei developers= at > > > least tried to re-implement the whole RDMA using rsocket, that didn't= land > > > only because of a perf regression. Meanwhile, Zhijian also provided = an > > > unit test, which we rely on recently to not break RDMA at the minimum. > > > > > > If we do not have known users, I sincerely want to discuss with you on > > > obsoletion and removal of COLO from qemu codebase. Do you see feasib= le? > > > > > > Zhijian, do you have any input here? =20 > > > > > > If we don't have any known users, I personally have no objection to rem= oving COLO. > > > > From my previous understanding, its use cases are rather limited, and = the checkpointing overhead is significant. > > Moreover, with the continuous development of Cloud Native over the past= decade, service-based > > FT/HA solutions have become very mature, which shrinks the use cases fo= r VM-based FT solutions even further. > > > > I think it's worth keeping if we have: > > > > - Active users who depend on it. > > - A unit test for the COLO framework. > > > > Thanks > > Zhijian > > > > =20 >=20 > Add CC Lukas. >=20 > [...] Hello Everyone, Thanks for bringing this to my attention. I will write a migration unit-test and take maintainership of the colo components. Peter, what is your plan with refactoring the migration code and where is the colo code blocking you? I have quite a few cleanup patches lying around. Are you open to take these in advance before the next merge window opens? Best regards, Lukas Straub --Sig_/kb=8f9B2PaZ=J7kJiCHBNsd Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEg/qxWKDZuPtyYo+kNasLKJxdslgFAmkkGaEACgkQNasLKJxd slgJIxAAovGtBOxdxWujLwOQpgQ+Gp1QUVoyAU+0jOUaMxU7LlE4/s3cEbvLEYoT UY+xFujDP1ko3ytRL861wQKw0TwMvnpX6V/lG10THI2so/+R9zNUxrBFxUoJg3q4 whpn7oJ7ICWcNS9kagri8dEJWt5tJjkH2ueHzmMcm05gtdosiNvWDjmrYChuaJr8 c+mOMniQDvC8vT4BX0UHIxhje05iHLitoLZ/36hWRHMdtR6dYtMFctFRL3zevX7w F+ARmYjnxChOqke2ftZfO8iT2QpYkoz9VcsGsrENDKha7v24mRtVtNOzKxaHa1k2 OdMpmuBPpyqdysWEBs6pzta7AIhkLyq7ad3D58m3UzmjI/MzbmgJDrF4+dn1q3vk clI1PbnANw+SEVN4yscOtxjqTh20c6gzj4mfW7iuuwaf/pNzz3qrUi5UnbRpWGi0 Y8GZLPZ2yDgGaVyFFs2Ao9cHTU+JrbJ73F2a6RqdWl8/984ZqFqE1CgKH4e2pjBG AjFULuY1nK2nQaO9RIUZOYs4dburKQ97frpmrhQ01PFQXpqT5cCF8hoUpl9nLSgw 1JVaSij97oGcPMoZ+p8zPndhTttrYx9WMjQOXICPsbgRfrP0iKcfnQdtmB01XOE3 1pX5TwjnZJcutOSlfS4BlvlQDOUgel29OnJ0FmjZ3wFFhNWpPiQ= =RWzs -----END PGP SIGNATURE----- --Sig_/kb=8f9B2PaZ=J7kJiCHBNsd--