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Szmigiero" , Peter Xu Cc: Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eric Blake , Markus Armbruster , =?utf-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: Re: [PATCH v3 16/24] migration/multifd: Send final SYNC only after device state is complete In-Reply-To: <0b8131dc6107841969d254e88e9d6e14220f1ea5.1731773021.git.maciej.szmigiero@oracle.com> References: <0b8131dc6107841969d254e88e9d6e14220f1ea5.1731773021.git.maciej.szmigiero@oracle.com> Date: Tue, 26 Nov 2024 17:52:47 -0300 Message-ID: <87mshln2e8.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.20 / 50.00]; BAYES_HAM(-2.90)[99.56%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[10]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:mid] Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no 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 "Maciej S. Szmigiero" writes: > From: "Maciej S. Szmigiero" > > Currently, ram_save_complete() sends a final SYNC multifd packet near this > function end, after sending all of the remaining RAM data. > > On the receive side, this SYNC packet will cause multifd channel threads > to block, waiting for the final sem_sync posting in > multifd_recv_terminate_threads(). > > However, multifd_recv_terminate_threads() won't be called until the > migration is complete, which causes a problem if multifd channels are > still required for transferring device state data after RAM transfer is > complete but before finishing the migration process. > > Defer sending the final SYNC packet to the end of sending of > post-switchover iterable data instead if device state transfer is possible. > > Signed-off-by: Maciej S. Szmigiero Reviewed-by: Fabiano Rosas I wonder whether we could just defer the sync for the !device_state case as well.