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Szmigiero" , =?utf-8?Q?C=C3=A9dric?= Le Goater , Alex Williamson , peterx@redhat.com, Avihai Horon Subject: Re: [PATCH v3 2/7] migration/multifd: Allow to sync with sender threads only In-Reply-To: <20241206224755.1108686-3-peterx@redhat.com> References: <20241206224755.1108686-1-peterx@redhat.com> <20241206224755.1108686-3-peterx@redhat.com> Date: Mon, 09 Dec 2024 17:52:13 -0300 Message-ID: <87wmg8a8aq.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; 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)[8]; 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=195.135.223.131; envelope-from=farosas@suse.de; helo=smtp-out2.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_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 Peter Xu writes: > Teach multifd_send_sync_main() to sync with threads only. > > We already have such requests, which is when mapped-ram is enabled with > multifd. In that case, no SYNC messages will be pushed to the stream when > multifd syncs the sender threads because there's no destination threads > waiting for that. The whole point of the sync is to make sure all threads > finished their jobs. > > So fundamentally we have a request to do the sync in different ways: > > - Either to sync the threads only, > - Or to sync the threads but also with the destination side. > > Mapped-ram did it already because of the use_packet check in the sync > handler of the sender thread. It works. > > However it may stop working when e.g. VFIO may start to reuse multifd > channels to push device states. In that case VFIO has similar request on > "thread-only sync" however we can't check a flag because such sync request > can still come from RAM which needs the on-wire notifications. > > Paving way for that by allowing the multifd_send_sync_main() to specify > what kind of sync the caller needs. We can use it for mapped-ram already. > > No functional change intended. > > Signed-off-by: Peter Xu Reviewed-by: Fabiano Rosas