Re: [Qemu-devel] [RFC PATCH v2 11/12] mc: introduce new capabilities to control micro-checkpointing

[Juan Quintela <quintela@redhat.com>]

mrhines@linux.vnet.ibm.com wrote:
> From: "Michael R. Hines" <mrhines@us.ibm.com>
>
> New capabilities include the use of RDMA acceleration,
> use of network buffering, and keepalive support, as documented
> in patch #1.
>
> Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
> ---
>  qapi-schema.json | 36 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 98abdac..1fdf208 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -720,10 +720,44 @@
>  # @auto-converge: If enabled, QEMU will automatically throttle down the guest
>  #          to speed up convergence of RAM migration. (since 1.6)
>  #
> +# @mc: The migration will never end, and the VM will instead be continuously
> +#          micro-checkpointed (MC). Use the command migrate-set-mc-delay to 
> +#          control the frequency at which the checkpoints occur. 
> +#          Disabled by default. (Since 2.x)
> +#
> +# @mc-net-disable: Deactivate network buffering against outbound network 
> +#          traffic while Micro-Checkpointing (@mc) is active.
> +#          Enabled by default. Disabling will make the MC protocol inconsistent
> +#          and potentially break network connections upon an actual failure.
> +#          Only for performance testing. (Since 2.x)

If it is dangerous, can we put dangerous/unsafe on the name?  Having an option that
can corrupt things make me nervous.

> +#
> +# @mc-rdma-copy: MC requires creating a local-memory checkpoint before
> +#          transmission to the destination. This requires heavy use of 
> +#          memcpy() which dominates the processor pipeline. This option 
> +#          makes use of *local* RDMA to perform the copy instead of the CPU.
> +#          Enabled by default only if the migration transport is RDMA.
> +#          Disabled by default otherwise. (Since 2.x)
> +#
> +# @rdma-keepalive: RDMA connections do not timeout by themselves if a peer
> +#         has disconnected prematurely or failed. User-level keepalives
> +#         allow the migration to abort cleanly if there is a problem with the
> +#         destination host. For debugging, this can be problematic as
> +#         the keepalive may cause the peer to abort prematurely if we are
> +#         at a GDB breakpoint, for example.
> +#         Enabled by default. (Since 2.x)
> +#
>  # Since: 1.2
>  ##
>  { 'enum': 'MigrationCapability',
> -  'data': ['xbzrle', 'x-rdma-pin-all', 'auto-converge', 'zero-blocks'] }
> +  'data': ['xbzrle', 
> +           'rdma-pin-all', 
> +           'auto-converge', 
> +           'zero-blocks',
> +           'mc', 
> +           'mc-net-disable',
> +           'mc-rdma-copy',
> +           'rdma-keepalive'
> +          ] }
>  
>  ##
>  # @MigrationCapabilityStatus

Thask, Juan.