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charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; RCPT_COUNT_SEVEN(0.00)[9]; MID_RHS_MATCH_FROM(0.00)[]; TO_DN_SOME(0.00)[] 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: > On Wed, Jun 12, 2024 at 07:15:19PM +0100, Daniel P. Berrang=C3=A9 wrote: >> IIUC, with the "fixed-ram" feature, the on-disk format of a saved VM >> should end up the same whether we're using traditional migration, or >> multifd migration. Use of multifd is simply an optimization that lets >> us write RAM in parallel to the file, with direct-io further optimizing. >>=20 >> There's also a clear break with libvirt between the existing on-disk >> format libvirt uses, and the new fixed-ram format. So we have no backwar= ds >> compatibilty concerns added from multifd, beyond what we already have to >> figure out when deciding on use of 'fixed-ram'.=20 >>=20 >> Thus I believe there is no downside to always using multifd for save >> images with fixed-ram, even if we only want nchannels=3D1. > > That sounds good. > > Just to double check with all of us: so we allow mapped-ram to be used in > whatever case when !dio, however we restrict dio only when with multifd= =3Don, > am I right? Yes. The restricting part is not yet in place. I'll add a multifd check to migrate_direct_io(): bool migrate_direct_io(void) { MigrationState *s =3D migrate_get_current(); return s->parameters.direct_io && s->capabilities[MIGRATION_CAPABILITY_MAPPED_RAM] && s->capabilities[MIGRATION_CAPABILITY_MULTIFD]; }