On Thu, Jan 06, 2022 at 07:13:40PM -0300, Leonardo Bras wrote:
> Add property that allows zero-copy migration of memory pages,
> and also includes a helper function migrate_use_zero_copy() 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 <leob...@redhat.com>
> ---
> qapi/migration.json | 24 ++++++++++++++++++++++++
> migration/migration.h | 5 +++++
> migration/migration.c | 32 ++++++++++++++++++++++++++++++++
> migration/socket.c | 5 +++++
> monitor/hmp-cmds.c | 6 ++++++
> 5 files changed, 72 insertions(+)
Reviewed-by: Daniel P. Berrangé <berra...@redhat.com>
>
> diff --git a/qapi/migration.json b/qapi/migration.json
> index bbfd48cf0b..2e62ea6ebd 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -730,6 +730,13 @@
> # will consume more CPU.
> # Defaults to 1. (Since 5.0)
> #
> +# @zero-copy: 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 7.0)
> +#
> # @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
> @@ -769,6 +776,7 @@
> 'xbzrle-cache-size', 'max-postcopy-bandwidth',
> 'max-cpu-throttle', 'multifd-compression',
> 'multifd-zlib-level' ,'multifd-zstd-level',
> + { 'name': 'zero-copy', 'if' : 'CONFIG_LINUX'},
> 'block-bitmap-mapping' ] }
>
> ##
> @@ -895,6 +903,13 @@
> # will consume more CPU.
> # Defaults to 1. (Since 5.0)
> #
> +# @zero-copy: 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 7.0)
> +#
> # @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
> @@ -949,6 +964,7 @@
> '*multifd-compression': 'MultiFDCompression',
> '*multifd-zlib-level': 'uint8',
> '*multifd-zstd-level': 'uint8',
> + '*zero-copy': { 'type': 'bool', 'if': 'CONFIG_LINUX' },
> '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ] } }
The current zerocopy impl is for the send path.
Do you expect we might get zerocopy in the receive path
later ?
If so then either call this 'send-zero-copy', or change it
from a bool to an enum taking '["send", "recv", "both"]'.
I'd probably take the former and just rename it.
Regards,
Daniel
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