Re: [PATCH v11 3/7] migration: Add zero-copy-send parameter for QMP/HMP for Linux

[Markus Armbruster <armbru@redhat.com>]

Leonardo Bras <leobras@redhat.com> writes:

> Add property that allows zero-copy migration of memory pages
> on the sending side, and also includes a helper function
> migrate_use_zero_copy_send() to check if it's enabled.
>
> No code is introduced to actually do the migration, but it allow
> future implementations to enable/disable this feature.
>
> On non-Linux builds this parameter is compiled-out.
>
> Signed-off-by: Leonardo Bras <leobras@redhat.com>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> Acked-by: Markus Armbruster <armbru@redhat.com>
> ---
>  qapi/migration.json   | 24 ++++++++++++++++++++++++
>  migration/migration.h |  5 +++++
>  migration/migration.c | 32 ++++++++++++++++++++++++++++++++
>  migration/socket.c    | 11 +++++++++--
>  monitor/hmp-cmds.c    |  6 ++++++
>  5 files changed, 76 insertions(+), 2 deletions(-)
>
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 409eb086a2..04246481ce 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -741,6 +741,13 @@
>  #                      will consume more CPU.
>  #                      Defaults to 1. (Since 5.0)
>  #
> +# @zero-copy-send: Controls behavior on sending memory pages on migration.
> +#                  When true, enables a zero-copy mechanism for sending memory
> +#                  pages, if host supports it.
> +#                  Requires that QEMU be permitted to use locked memory for guest

Please wrap lines around column 75.  More of the same below.

> +#                  RAM pages.
> +#                  Defaults to false. (Since 7.1)
> +#
>  # @block-bitmap-mapping: Maps block nodes and bitmaps on them to
>  #                        aliases for the purpose of dirty bitmap migration.  Such
>  #                        aliases may for example be the corresponding names on the
> @@ -780,6 +787,7 @@
>             'xbzrle-cache-size', 'max-postcopy-bandwidth',
>             'max-cpu-throttle', 'multifd-compression',
>             'multifd-zlib-level' ,'multifd-zstd-level',
> +           { 'name': 'zero-copy-send', 'if' : 'CONFIG_LINUX'},
>             'block-bitmap-mapping' ] }
>  
>  ##
> @@ -906,6 +914,13 @@
>  #                      will consume more CPU.
>  #                      Defaults to 1. (Since 5.0)
>  #
> +# @zero-copy-send: Controls behavior on sending memory pages on migration.
> +#                  When true, enables a zero-copy mechanism for sending memory
> +#                  pages, if host supports it.
> +#                  Requires that QEMU be permitted to use locked memory for guest
> +#                  RAM pages.
> +#                  Defaults to false. (Since 7.1)
> +#
>  # @block-bitmap-mapping: Maps block nodes and bitmaps on them to
>  #                        aliases for the purpose of dirty bitmap migration.  Such
>  #                        aliases may for example be the corresponding names on the
> @@ -960,6 +975,7 @@
>              '*multifd-compression': 'MultiFDCompression',
>              '*multifd-zlib-level': 'uint8',
>              '*multifd-zstd-level': 'uint8',
> +            '*zero-copy-send': { 'type': 'bool', 'if': 'CONFIG_LINUX' },
>              '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ] } }
>  
>  ##
> @@ -1106,6 +1122,13 @@
>  #                      will consume more CPU.
>  #                      Defaults to 1. (Since 5.0)
>  #
> +# @zero-copy-send: Controls behavior on sending memory pages on migration.
> +#                  When true, enables a zero-copy mechanism for sending memory
> +#                  pages, if host supports it.
> +#                  Requires that QEMU be permitted to use locked memory for guest
> +#                  RAM pages.
> +#                  Defaults to false. (Since 7.1)
> +#
>  # @block-bitmap-mapping: Maps block nodes and bitmaps on them to
>  #                        aliases for the purpose of dirty bitmap migration.  Such
>  #                        aliases may for example be the corresponding names on the
> @@ -1158,6 +1181,7 @@
>              '*multifd-compression': 'MultiFDCompression',
>              '*multifd-zlib-level': 'uint8',
>              '*multifd-zstd-level': 'uint8',
> +            '*zero-copy-send': { 'type': 'bool', 'if': 'CONFIG_LINUX' },
>              '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ] } }
>  
>  ##

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