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 | 15 ++++++++++++---
migration/migration-hmp-cmds.c | 10 ++++++++++
migration/options.c | 30 ++++++++++++++++++++++++++++++
migration/options.h | 1 +
qapi/migration.json | 17 ++++++++++++++---
util/osdep.c | 9 +++++++++
7 files changed, 78 insertions(+), 6 deletions(-)
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 475a1c62ff..ea5d29ab9b 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -597,6 +597,8 @@ 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 ad75225f43..3d3c58ecad 100644
--- a/migration/file.c
+++ b/migration/file.c
@@ -11,9 +11,9 @@
#include "qemu/error-report.h"
#include "channel.h"
#include "file.h"
-#include "migration.h"
#include "io/channel-file.h"
#include "io/channel-util.h"
+#include "migration.h"
#include "options.h"
#include "trace.h"
@@ -77,9 +77,18 @@ 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_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 a82597f18e..eab5ac3588 100644
--- a/migration/migration-hmp-cmds.c
+++ b/migration/migration-hmp-cmds.c
@@ -387,6 +387,12 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict
*qdict)
monitor_printf(mon, "%s: %" PRIu64 " MB/s\n",
MigrationParameter_str(MIGRATION_PARAMETER_VCPU_DIRTY_LIMIT),
params->vcpu_dirty_limit);
+
+ 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);
@@ -661,6 +667,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict
*qdict)
p->has_vcpu_dirty_limit = true;
visit_type_size(v, param, &p->vcpu_dirty_limit, &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 2193d69e71..6d0e3c26ae 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -817,6 +817,22 @@ int migrate_decompress_threads(void)
return s->parameters.decompress_threads;
}
+bool migrate_direct_io(void)
+{
+ MigrationState *s = migrate_get_current();
+
+ /* For now O_DIRECT is only supported with fixed-ram */
+ if (!s->capabilities[MIGRATION_CAPABILITY_FIXED_RAM]) {
+ return false;
+ }
+
+ if (s->parameters.has_direct_io) {
+ return s->parameters.direct_io;
+ }
+
+ return false;
+}
+
uint64_t migrate_downtime_limit(void)
{
MigrationState *s = migrate_get_current();
@@ -1025,6 +1041,11 @@ MigrationParameters *qmp_query_migrate_parameters(Error
**errp)
params->has_vcpu_dirty_limit = true;
params->vcpu_dirty_limit = s->parameters.vcpu_dirty_limit;
+ if (s->parameters.has_direct_io) {
+ params->has_direct_io = true;
+ params->direct_io = s->parameters.direct_io;
+ }
+
return params;
}
@@ -1059,6 +1080,7 @@ void migrate_params_init(MigrationParameters *params)
params->has_announce_step = true;
params->has_x_vcpu_dirty_limit_period = true;
params->has_vcpu_dirty_limit = true;
+ params->has_direct_io = qemu_has_direct_io();
}
/*
@@ -1356,6 +1378,10 @@ static void
migrate_params_test_apply(MigrateSetParameters *params,
if (params->has_vcpu_dirty_limit) {
dest->vcpu_dirty_limit = params->vcpu_dirty_limit;
}
+
+ if (params->has_direct_io) {
+ dest->direct_io = params->direct_io;
+ }
}
static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
@@ -1486,6 +1512,10 @@ static void migrate_params_apply(MigrateSetParameters
*params, Error **errp)
if (params->has_vcpu_dirty_limit) {
s->parameters.vcpu_dirty_limit = params->vcpu_dirty_limit;
}
+
+ 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 01bba5b928..280f86bed1 100644
--- a/migration/options.h
+++ b/migration/options.h
@@ -82,6 +82,7 @@ uint8_t migrate_cpu_throttle_increment(void);
uint8_t migrate_cpu_throttle_initial(void);
bool migrate_cpu_throttle_tailslow(void);
int migrate_decompress_threads(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 1317dd32ab..3eb9e2c9b5 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -840,6 +840,9 @@
# @vcpu-dirty-limit: Dirtyrate limit (MB/s) during live migration.
# Defaults to 1. (Since 8.1)
#
+# @direct-io: Open migration files with O_DIRECT when possible. Not
+# all migration transports support this. (since 8.1)
+#
# Features:
#
# @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period
@@ -864,7 +867,7 @@
'multifd-zlib-level', 'multifd-zstd-level',
'block-bitmap-mapping',
{ 'name': 'x-vcpu-dirty-limit-period', 'features': ['unstable'] },
- 'vcpu-dirty-limit'] }
+ 'vcpu-dirty-limit', 'direct-io'] }
##
# @MigrateSetParameters:
@@ -1016,6 +1019,9 @@
# @vcpu-dirty-limit: Dirtyrate limit (MB/s) during live migration.
# Defaults to 1. (Since 8.1)
#
+# @direct-io: Open migration files with O_DIRECT when possible. Not
+# all migration transports support this. (since 8.1)
+#
# Features:
#
# @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period
@@ -1058,7 +1064,8 @@
'*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ],
'*x-vcpu-dirty-limit-period': { 'type': 'uint64',
'features': [ 'unstable' ] },
- '*vcpu-dirty-limit': 'uint64'} }
+ '*vcpu-dirty-limit': 'uint64',
+ '*direct-io': 'bool' } }
##
# @migrate-set-parameters:
@@ -1230,6 +1237,9 @@
# @vcpu-dirty-limit: Dirtyrate limit (MB/s) during live migration.
# Defaults to 1. (Since 8.1)
#
+# @direct-io: Open migration files with O_DIRECT when possible. Not
+# all migration transports support this. (since 8.1)
+#
# Features:
#
# @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period
@@ -1269,7 +1279,8 @@
'*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ],
'*x-vcpu-dirty-limit-period': { 'type': 'uint64',
'features': [ 'unstable' ] },
- '*vcpu-dirty-limit': 'uint64'} }
+ '*vcpu-dirty-limit': 'uint64',
+ '*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
