From b43b61d5bee522dadf44b472af71aab7235c13d5 Mon Sep 17 00:00:00 2001 From: Fabiano Rosas Date: Mon, 17 Jun 2024 15:57:26 -0300 Subject: [PATCH] migration: Add direct-io parameter Add the direct-io migration parameter that tells the migration code to use O_DIRECT when opening the migration stream file whenever possible. This is currently only used with the mapped-ram migration that has a clear window guaranteed to perform aligned writes. Acked-by: Markus Armbruster Reviewed-by: Peter Xu Signed-off-by: Fabiano Rosas --- include/qemu/osdep.h | 2 ++ migration/migration-hmp-cmds.c | 11 +++++++++++ migration/options.c | 35 ++++++++++++++++++++++++++++++++++ migration/options.h | 1 + qapi/migration.json | 21 +++++++++++++++++--- util/osdep.c | 9 +++++++++ 6 files changed, 76 insertions(+), 3 deletions(-) diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index f61edcfdc2..191916f38e 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -612,6 +612,8 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive); bool qemu_has_ofd_lock(void); #endif +bool qemu_has_direct_io(void); + #if defined(__HAIKU__) && defined(__i386__) #define FMT_pid "%ld" #elif defined(WIN64) diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c index 9f0e8029e0..7d608d26e1 100644 --- a/migration/migration-hmp-cmds.c +++ b/migration/migration-hmp-cmds.c @@ -351,6 +351,13 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict) monitor_printf(mon, "%s: %s\n", MigrationParameter_str(MIGRATION_PARAMETER_MODE), qapi_enum_lookup(&MigMode_lookup, params->mode)); + + if (params->has_direct_io) { + monitor_printf(mon, "%s: %s\n", + MigrationParameter_str( + MIGRATION_PARAMETER_DIRECT_IO), + params->direct_io ? "on" : "off"); + } } qapi_free_MigrationParameters(params); @@ -624,6 +631,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict) p->has_mode = true; visit_type_MigMode(v, param, &p->mode, &err); break; + case MIGRATION_PARAMETER_DIRECT_IO: + p->has_direct_io = true; + visit_type_bool(v, param, &p->direct_io, &err); + break; default: assert(0); } diff --git a/migration/options.c b/migration/options.c index 5ab5b6d85d..645f55003d 100644 --- a/migration/options.c +++ b/migration/options.c @@ -702,6 +702,25 @@ bool migrate_cpu_throttle_tailslow(void) return s->parameters.cpu_throttle_tailslow; } +bool migrate_direct_io(void) +{ + MigrationState *s = migrate_get_current(); + + /* + * O_DIRECT is only supported with mapped-ram and multifd. + * + * mapped-ram is needed because filesystems impose restrictions on + * O_DIRECT IO alignment (see MAPPED_RAM_FILE_OFFSET_ALIGNMENT). + * + * multifd is needed to keep the unaligned portion of the stream + * isolated to the main migration thread while multifd channels + * process the aligned data with O_DIRECT enabled. + */ + return s->parameters.direct_io && + s->capabilities[MIGRATION_CAPABILITY_MAPPED_RAM] && + s->capabilities[MIGRATION_CAPABILITY_MULTIFD]; +} + uint64_t migrate_downtime_limit(void) { MigrationState *s = migrate_get_current(); @@ -905,6 +924,8 @@ MigrationParameters *qmp_query_migrate_parameters(Error **errp) params->mode = s->parameters.mode; params->has_zero_page_detection = true; params->zero_page_detection = s->parameters.zero_page_detection; + params->has_direct_io = true; + params->direct_io = s->parameters.direct_io; return params; } @@ -937,6 +958,7 @@ void migrate_params_init(MigrationParameters *params) params->has_vcpu_dirty_limit = true; params->has_mode = true; params->has_zero_page_detection = true; + params->has_direct_io = true; } /* @@ -1110,6 +1132,11 @@ bool migrate_params_check(MigrationParameters *params, Error **errp) return false; } + if (params->has_direct_io && params->direct_io && !qemu_has_direct_io()) { + error_setg(errp, "No build-time support for direct-io"); + return false; + } + return true; } @@ -1216,6 +1243,10 @@ static void migrate_params_test_apply(MigrateSetParameters *params, if (params->has_zero_page_detection) { dest->zero_page_detection = params->zero_page_detection; } + + if (params->has_direct_io) { + dest->direct_io = params->direct_io; + } } static void migrate_params_apply(MigrateSetParameters *params, Error **errp) @@ -1341,6 +1372,10 @@ static void migrate_params_apply(MigrateSetParameters *params, Error **errp) if (params->has_zero_page_detection) { s->parameters.zero_page_detection = params->zero_page_detection; } + + if (params->has_direct_io) { + s->parameters.direct_io = params->direct_io; + } } void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp) diff --git a/migration/options.h b/migration/options.h index 4b21cc2669..a2397026db 100644 --- a/migration/options.h +++ b/migration/options.h @@ -69,6 +69,7 @@ uint32_t migrate_checkpoint_delay(void); uint8_t migrate_cpu_throttle_increment(void); uint8_t migrate_cpu_throttle_initial(void); bool migrate_cpu_throttle_tailslow(void); +bool migrate_direct_io(void); uint64_t migrate_downtime_limit(void); uint8_t migrate_max_cpu_throttle(void); uint64_t migrate_max_bandwidth(void); diff --git a/qapi/migration.json b/qapi/migration.json index 470f746cc5..de6c8b0444 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -821,6 +821,10 @@ # See description in @ZeroPageDetection. Default is 'multifd'. # (since 9.0) # +# @direct-io: Open migration files with O_DIRECT when possible. This +# only has effect if the @mapped-ram capability is enabled. +# (Since 9.1) +# # Features: # # @unstable: Members @x-checkpoint-delay and @@ -845,7 +849,8 @@ { 'name': 'x-vcpu-dirty-limit-period', 'features': ['unstable'] }, 'vcpu-dirty-limit', 'mode', - 'zero-page-detection'] } + 'zero-page-detection', + 'direct-io'] } ## # @MigrateSetParameters: @@ -991,6 +996,10 @@ # See description in @ZeroPageDetection. Default is 'multifd'. # (since 9.0) # +# @direct-io: Open migration files with O_DIRECT when possible. This +# only has effect if the @mapped-ram capability is enabled. +# (Since 9.1) +# # Features: # # @unstable: Members @x-checkpoint-delay and @@ -1030,7 +1039,8 @@ 'features': [ 'unstable' ] }, '*vcpu-dirty-limit': 'uint64', '*mode': 'MigMode', - '*zero-page-detection': 'ZeroPageDetection'} } + '*zero-page-detection': 'ZeroPageDetection', + '*direct-io': 'bool' } } ## # @migrate-set-parameters: @@ -1190,6 +1200,10 @@ # See description in @ZeroPageDetection. Default is 'multifd'. # (since 9.0) # +# @direct-io: Open migration files with O_DIRECT when possible. This +# only has effect if the @mapped-ram capability is enabled. +# (Since 9.1) +# # Features: # # @unstable: Members @x-checkpoint-delay and @@ -1226,7 +1240,8 @@ 'features': [ 'unstable' ] }, '*vcpu-dirty-limit': 'uint64', '*mode': 'MigMode', - '*zero-page-detection': 'ZeroPageDetection'} } + '*zero-page-detection': 'ZeroPageDetection', + '*direct-io': 'bool' } } ## # @query-migrate-parameters: diff --git a/util/osdep.c b/util/osdep.c index 5bbfdfac7a..770369831b 100644 --- a/util/osdep.c +++ b/util/osdep.c @@ -282,6 +282,15 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive) } #endif +bool qemu_has_direct_io(void) +{ +#ifdef O_DIRECT + return true; +#else + return false; +#endif +} + static int qemu_open_cloexec(const char *name, int flags, mode_t mode) { int ret;