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 for the secondary channels of fixed-ram
migration, which can guarantee that writes are page aligned.
However the parameter could be made to affect other types of
file-based migrations in the future.
Signed-off-by: Fabiano Rosas <faro...@suse.de>
---
include/qemu/osdep.h | 2 ++
migration/file.c | 13 +++++++++++--
migration/migration-hmp-cmds.c | 9 +++++++++
migration/migration.c | 32 ++++++++++++++++++++++++++++++++
migration/migration.h | 1 +
qapi/migration.json | 17 ++++++++++++++---
util/osdep.c | 9 +++++++++
7 files changed, 78 insertions(+), 5 deletions(-)
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 9eff0be95b..19c1d5f999 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -570,6 +570,8 @@ 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/file.c b/migration/file.c
index 6f40894488..1a40da097d 100644
--- a/migration/file.c
+++ b/migration/file.c
@@ -43,9 +43,18 @@ void file_send_channel_create(QIOTaskFunc f, void *data)
QIOChannelFile *ioc;
QIOTask *task;
Error *errp = NULL;
+ int flags = outgoing_args.flags;
- ioc = qio_channel_file_new_path(outgoing_args.fname,
- outgoing_args.flags,
+ if (migrate_use_direct_io() && qemu_has_direct_io()) {
+ /*
+ * Enable O_DIRECT for the secondary channels. These are used
+ * for sending ram pages and writes should be guaranteed to be
+ * aligned to at least page size.
+ */
+ flags |= O_DIRECT;
+ }
+
+ ioc = qio_channel_file_new_path(outgoing_args.fname, flags,
outgoing_args.mode, &errp);
if (!ioc) {
file_migration_cancel(errp);
diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
index 72519ea99f..c9a8d84714 100644
--- a/migration/migration-hmp-cmds.c
+++ b/migration/migration-hmp-cmds.c
@@ -344,6 +344,11 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict
*qdict)
}
}
}
+ 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);
@@ -600,6 +605,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict
*qdict)
error_setg(&err, "The block-bitmap-mapping parameter can only be set "
"through QMP");
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/migration.c b/migration/migration.c
index 77d24a5114..65798171e4 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1022,6 +1022,11 @@ MigrationParameters *qmp_query_migrate_parameters(Error
**errp)
s->parameters.block_bitmap_mapping);
}
+ if (s->parameters.has_direct_io) {
+ params->has_direct_io = true;
+ params->direct_io = s->parameters.direct_io;
+ }
+
return params;
}
@@ -1782,6 +1787,10 @@ static void
migrate_params_test_apply(MigrateSetParameters *params,
dest->has_block_bitmap_mapping = true;
dest->block_bitmap_mapping = params->block_bitmap_mapping;
}
+
+ if (params->has_direct_io) {
+ dest->direct_io = params->direct_io;
+ }
}
static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
@@ -1904,6 +1913,10 @@ static void migrate_params_apply(MigrateSetParameters
*params, Error **errp)
QAPI_CLONE(BitmapMigrationNodeAliasList,
params->block_bitmap_mapping);
}
+
+ if (params->has_direct_io) {
+ s->parameters.direct_io = params->direct_io;
+ }
}
void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
@@ -2885,6 +2898,24 @@ bool migrate_postcopy_preempt(void)
return s->enabled_capabilities[MIGRATION_CAPABILITY_POSTCOPY_PREEMPT];
}
+bool migrate_use_direct_io(void)
+{
+ MigrationState *s;
+
+ /* For now O_DIRECT is only supported with fixed-ram */
+ if (!migrate_fixed_ram()) {
+ return false;
+ }
+
+ s = migrate_get_current();
+
+ if (s->parameters.has_direct_io) {
+ return s->parameters.direct_io;
+ }
+
+ return false;
+}
+
/* migration thread support */
/*
* Something bad happened to the RP stream, mark an error
@@ -4666,6 +4697,7 @@ static void migration_instance_init(Object *obj)
params->has_announce_max = true;
params->has_announce_rounds = true;
params->has_announce_step = true;
+ params->has_direct_io = qemu_has_direct_io();
qemu_sem_init(&ms->postcopy_pause_sem, 0);
qemu_sem_init(&ms->postcopy_pause_rp_sem, 0);
diff --git a/migration/migration.h b/migration/migration.h
index 8459201958..e0c9c78570 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -422,6 +422,7 @@ bool migrate_ignore_shared(void);
bool migrate_validate_uuid(void);
int migrate_fixed_ram(void);
bool migrate_multifd_use_packets(void);
+bool migrate_use_direct_io(void);
bool migrate_auto_converge(void);
bool migrate_use_multifd(void);
bool migrate_pause_before_switchover(void);
diff --git a/qapi/migration.json b/qapi/migration.json
index 22eea58ce3..2190d98ded 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -776,6 +776,9 @@
# block device name if there is one, and to their node
name
# otherwise. (Since 5.2)
#
+# @direct-io: Open migration files with O_DIRECT when possible. Not
+# all migration transports support this. (since 8.1)
+#
# Features:
# @unstable: Member @x-checkpoint-delay is experimental.
#
@@ -796,7 +799,7 @@
'xbzrle-cache-size', 'max-postcopy-bandwidth',
'max-cpu-throttle', 'multifd-compression',
'multifd-zlib-level' ,'multifd-zstd-level',
- 'block-bitmap-mapping' ] }
+ 'block-bitmap-mapping', 'direct-io' ] }
##
# @MigrateSetParameters:
@@ -941,6 +944,9 @@
# block device name if there is one, and to their node
name
# otherwise. (Since 5.2)
#
+# @direct-io: Open migration files with O_DIRECT when possible. Not
+# all migration transports support this. (since 8.1)
+#
# Features:
# @unstable: Member @x-checkpoint-delay is experimental.
#
@@ -976,7 +982,8 @@
'*multifd-compression': 'MultiFDCompression',
'*multifd-zlib-level': 'uint8',
'*multifd-zstd-level': 'uint8',
- '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ] } }
+ '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ],
+ '*direct-io': 'bool' } }
##
# @migrate-set-parameters:
@@ -1141,6 +1148,9 @@
# block device name if there is one, and to their node
name
# otherwise. (Since 5.2)
#
+# @direct-io: Open migration files with O_DIRECT when possible. Not
+# all migration transports support this. (since 8.1)
+#
# Features:
# @unstable: Member @x-checkpoint-delay is experimental.
#
@@ -1174,7 +1184,8 @@
'*multifd-compression': 'MultiFDCompression',
'*multifd-zlib-level': 'uint8',
'*multifd-zstd-level': 'uint8',
- '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ] } }
+ '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ],
+ '*direct-io': 'bool' } }
##
# @query-migrate-parameters:
diff --git a/util/osdep.c b/util/osdep.c
index e996c4744a..d0227a60ab 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -277,6 +277,15 @@ 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;
--
2.35.3
