On Tue, 2022-08-02 at 08:39 +0200, Juan Quintela wrote:
> We have to enable it by default until we introduce the new code.
>
> Signed-off-by: Juan Quintela <quint...@redhat.com>
>
> ---
>
> Change it to a capability. As capabilities are off by default, have
> to change MULTIFD_ZERO_PAGE to MAIN_ZERO_PAGE, so it is false for
> default, and true for older versions.
IIUC, the idea of a capability is to introduce some new features to the code,
and let users enable or disable it.
If it introduce a new capability, is not very intuitive to think that it will be
always true for older versions, and false for new ones.
I would suggest adding it as MULTIFD_ZERO_PAGE, and let it disabled for now.
When the full feature gets introduced, the capability could be enabled by
default, if desired.
What do you think?
Best regards,
Leo
> ---
> qapi/migration.json | 8 +++++++-
> migration/migration.h | 1 +
> hw/core/machine.c | 1 +
> migration/migration.c | 16 +++++++++++++++-
> 4 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 81185d4311..dc981236ff 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -472,12 +472,18 @@
> # Requires that QEMU be permitted to use locked memory
> # for guest RAM pages.
> # (since 7.1)
> +#
> # @postcopy-preempt: If enabled, the migration process will allow postcopy
> # requests to preempt precopy stream, so postcopy requests
> # will be handled faster. This is a performance feature
> and
> # should not affect the correctness of postcopy migration.
> # (since 7.1)
> #
> +# @main-zero-page: If enabled, the detection of zero pages will be
> +# done on the main thread. Otherwise it is done on
> +# the multifd threads.
> +# (since 7.1)
> +#
> # Features:
> # @unstable: Members @x-colo and @x-ignore-shared are experimental.
> #
> @@ -492,7 +498,7 @@
> 'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
> { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
> 'validate-uuid', 'background-snapshot',
> - 'zero-copy-send', 'postcopy-preempt'] }
> + 'zero-copy-send', 'postcopy-preempt', 'main-zero-page'] }
>
> ##
> # @MigrationCapabilityStatus:
> diff --git a/migration/migration.h b/migration/migration.h
> index cdad8aceaa..58b245b138 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -415,6 +415,7 @@ int migrate_multifd_channels(void);
> MultiFDCompression migrate_multifd_compression(void);
> int migrate_multifd_zlib_level(void);
> int migrate_multifd_zstd_level(void);
> +bool migrate_use_main_zero_page(void);
>
> #ifdef CONFIG_LINUX
> bool migrate_use_zero_copy_send(void);
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index a673302cce..2624b75ab4 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -43,6 +43,7 @@
> GlobalProperty hw_compat_7_0[] = {
> { "arm-gicv3-common", "force-8-bit-prio", "on" },
> { "nvme-ns", "eui64-default", "on"},
> + { "migration", "main-zero-page", "true" },
> };
> const size_t hw_compat_7_0_len = G_N_ELEMENTS(hw_compat_7_0);
>
> diff --git a/migration/migration.c b/migration/migration.c
> index e03f698a3c..ce3e5cc0cd 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -164,7 +164,8 @@
> INITIALIZE_MIGRATE_CAPS_SET(check_caps_background_snapshot,
> MIGRATION_CAPABILITY_XBZRLE,
> MIGRATION_CAPABILITY_X_COLO,
> MIGRATION_CAPABILITY_VALIDATE_UUID,
> - MIGRATION_CAPABILITY_ZERO_COPY_SEND);
> + MIGRATION_CAPABILITY_ZERO_COPY_SEND,
> + MIGRATION_CAPABILITY_MAIN_ZERO_PAGE);
>
> /* When we add fault tolerance, we could have several
> migrations at once. For now we don't need to add
> @@ -2592,6 +2593,17 @@ bool migrate_use_multifd(void)
> return s->enabled_capabilities[MIGRATION_CAPABILITY_MULTIFD];
> }
>
> +bool migrate_use_main_zero_page(void)
> +{
> + MigrationState *s;
> +
> + s = migrate_get_current();
> +
> + // We will enable this when we add the right code.
> + // return s->enabled_capabilities[MIGRATION_CAPABILITY_MAIN_ZERO_PAGE];
> + return true;
> +}
> +
> bool migrate_pause_before_switchover(void)
> {
> MigrationState *s;
> @@ -4406,6 +4418,8 @@ static Property migration_properties[] = {
> DEFINE_PROP_MIG_CAP("x-zero-copy-send",
> MIGRATION_CAPABILITY_ZERO_COPY_SEND),
> #endif
> + DEFINE_PROP_MIG_CAP("main-zero-page",
> + MIGRATION_CAPABILITY_MAIN_ZERO_PAGE),
>
> DEFINE_PROP_END_OF_LIST(),
> };
