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David Alan Gilbert" , "Daniel P . Berrange" , Leonardo Bras Soares Passos , peterx@redhat.com, Juan Quintela Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1648676630922100002 Content-Type: text/plain; charset="utf-8"; x-default="true" Firstly, postcopy already preempts precopy due to the fact that we do unqueue_page() first before looking into dirty bits. However that's not enough, e.g., when there're host huge page enabled, when sending a precopy huge page, a postcopy request needs to wait until the who= le huge page that is sending to finish. That could introduce quite some delay, the bigger the huge page is the larger delay it'll bring. This patch adds a new capability to allow postcopy requests to preempt exis= ting precopy page during sending a huge page, so that postcopy requests can be serviced even faster. Meanwhile to send it even faster, bypass the precopy stream by providing a standalone postcopy socket for sending requested pages. Since the new behavior will not be compatible with the old behavior, this w= ill not be the default, it's enabled only when the new capability is set on both src/dst QEMUs. This patch only adds the capability itself, the logic will be added in foll= ow up patches. Reviewed-by: Dr. David Alan Gilbert Signed-off-by: Peter Xu --- migration/migration.c | 23 +++++++++++++++++++++++ migration/migration.h | 1 + qapi/migration.json | 8 +++++++- 3 files changed, 31 insertions(+), 1 deletion(-) diff --git a/migration/migration.c b/migration/migration.c index 21fcf5102f..76e6ada524 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1235,6 +1235,11 @@ static bool migrate_caps_check(bool *cap_list, error_setg(errp, "Postcopy is not compatible with ignore-share= d"); return false; } + + if (cap_list[MIGRATION_CAPABILITY_MULTIFD]) { + error_setg(errp, "Multifd is not supported in postcopy"); + return false; + } } =20 if (cap_list[MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT]) { @@ -1278,6 +1283,13 @@ static bool migrate_caps_check(bool *cap_list, return false; } =20 + if (cap_list[MIGRATION_CAPABILITY_POSTCOPY_PREEMPT]) { + if (!cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM]) { + error_setg(errp, "Postcopy preempt requires postcopy-ram"); + return false; + } + } + return true; } =20 @@ -2627,6 +2639,15 @@ bool migrate_background_snapshot(void) return s->enabled_capabilities[MIGRATION_CAPABILITY_BACKGROUND_SNAPSHO= T]; } =20 +bool migrate_postcopy_preempt(void) +{ + MigrationState *s; + + s =3D migrate_get_current(); + + return s->enabled_capabilities[MIGRATION_CAPABILITY_POSTCOPY_PREEMPT]; +} + /* migration thread support */ /* * Something bad happened to the RP stream, mark an error @@ -4237,6 +4258,8 @@ static Property migration_properties[] =3D { DEFINE_PROP_MIG_CAP("x-compress", MIGRATION_CAPABILITY_COMPRESS), DEFINE_PROP_MIG_CAP("x-events", MIGRATION_CAPABILITY_EVENTS), DEFINE_PROP_MIG_CAP("x-postcopy-ram", MIGRATION_CAPABILITY_POSTCOPY_RA= M), + DEFINE_PROP_MIG_CAP("x-postcopy-preempt", + MIGRATION_CAPABILITY_POSTCOPY_PREEMPT), DEFINE_PROP_MIG_CAP("x-colo", MIGRATION_CAPABILITY_X_COLO), DEFINE_PROP_MIG_CAP("x-release-ram", MIGRATION_CAPABILITY_RELEASE_RAM), DEFINE_PROP_MIG_CAP("x-block", MIGRATION_CAPABILITY_BLOCK), diff --git a/migration/migration.h b/migration/migration.h index a863032b71..af4bcb19c2 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -394,6 +394,7 @@ int migrate_decompress_threads(void); bool migrate_use_events(void); bool migrate_postcopy_blocktime(void); bool migrate_background_snapshot(void); +bool migrate_postcopy_preempt(void); =20 /* Sending on the return path - generic and then for each message type */ void migrate_send_rp_shut(MigrationIncomingState *mis, diff --git a/qapi/migration.json b/qapi/migration.json index 18e2610e88..3523f23386 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -463,6 +463,12 @@ # procedure starts. The VM RAM is saved with running= VM. # (since 6.0) # +# @postcopy-preempt: If enabled, the migration process will allow postcopy +# requests to preempt precopy stream, so postcopy reque= sts +# will be handled faster. This is a performance featur= e and +# should not affect the correctness of postcopy migrati= on. +# (since 7.0) +# # Features: # @unstable: Members @x-colo and @x-ignore-shared are experimental. # @@ -476,7 +482,7 @@ 'block', 'return-path', 'pause-before-switchover', 'multifd', 'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate', { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] }, - 'validate-uuid', 'background-snapshot'] } + 'validate-uuid', 'background-snapshot', 'postcopy-preempt'] } =20 ## # @MigrationCapabilityStatus: --=20 2.32.0