Het Gala <het.g...@nutanix.com> writes: > On 26/07/22 4:43 pm, Daniel P. Berrangé wrote: >> On Thu, Jul 21, 2022 at 07:56:15PM +0000, Het Gala wrote: >>> i) Modified the format of the qemu monitor command : 'migrate' by adding a >>> list, >>> each element in the list consisting of multifd connection parameters: >>> source >>> uri, destination uri and of the number of multifd channels between each >>> pair. >>> >>> ii) Information of all multifd connection parameters' list and length of the >>> list is stored in 'OutgoingMigrateParams' struct. >>> >>> Suggested-by: Manish Mishra <manish.mis...@nutanix.com> >>> Signed-off-by: Het Gala <het.g...@nutanix.com> >>> --- >>> migration/migration.c | 52 +++++++++++++++++++++++++++++-------- >>> migration/socket.c | 60 ++++++++++++++++++++++++++++++++++++++++--- >>> migration/socket.h | 19 +++++++++++++- >>> monitor/hmp-cmds.c | 1 + >>> qapi/migration.json | 47 +++++++++++++++++++++++++++++---- >>> 5 files changed, 160 insertions(+), 19 deletions(-) >>> >>> diff --git a/qapi/migration.json b/qapi/migration.json >>> index 81185d4311..456247af8f 100644 >>> --- a/qapi/migration.json >>> +++ b/qapi/migration.json >>> @@ -1449,12 +1449,37 @@ >>> ## >>> { 'command': 'migrate-continue', 'data': {'state': 'MigrationStatus'} } >>> +## >>> +# @MigrateUriParameter: >>> +# >>> +# Information regarding which source interface is connected to which >>> +# destination interface and number of multifd channels over each interface. >>> +# >>> +# @source-uri: uri of the source VM. Default port number is 0. >>> +# >>> +# @destination-uri: uri of the destination VM >>> +# >>> +# @multifd-channels: number of parallel multifd channels used to migrate >>> data >>> +# for specific source-uri and destination-uri. Default >>> value >>> +# in this case is 2 (Since 7.1) >>> +# >>> +## >>> +{ 'struct' : 'MigrateUriParameter', >>> + 'data' : { 'source-uri' : 'str', >>> + 'destination-uri' : 'str', >>> + '*multifd-channels' : 'uint8'} } >>> + >>> ## >>> # @migrate: >>> # >>> # Migrates the current running guest to another Virtual Machine. >>> # >>> # @uri: the Uniform Resource Identifier of the destination VM >>> +# for migration thread >>> +# >>> +# @multi-fd-uri-list: list of pair of source and destination VM Uniform >>> +# Resource Identifiers with number of multifd-channels >>> +# for each pair >>> # >>> # @blk: do block migration (full disk copy) >>> # >>> @@ -1474,20 +1499,32 @@ >>> # 1. The 'query-migrate' command should be used to check migration's >>> progress >>> # and final result (this information is provided by the 'status' >>> member) >>> # >>> -# 2. All boolean arguments default to false >>> +# 2. The uri argument should have the Uniform Resource Identifier of >>> default >>> +# destination VM. This connection will be bound to default network >>> # >>> -# 3. The user Monitor's "detach" argument is invalid in QMP and should not >>> +# 3. All boolean arguments default to false >>> +# >>> +# 4. The user Monitor's "detach" argument is invalid in QMP and should not >>> # be used >>> # >>> # Example: >>> # >>> -# -> { "execute": "migrate", "arguments": { "uri": "tcp:0:4446" } } >>> +# -> { "execute": "migrate", >>> +# "arguments": { >>> +# "uri": "tcp:0:4446", >>> +# "multi-fd-uri-list": [ { "source-uri": "tcp::6900", >>> +# "destination-uri": "tcp:0:4480", >>> +# "multifd-channels": 4}, >>> +# { "source-uri": "tcp:10.0.0.0: ", >>> +# "destination-uri": "tcp:11.0.0.0:7789", >>> +# "multifd-channels": 5} ] } } >>> # <- { "return": {} } >>> # >>> ## >>> { 'command': 'migrate', >>> - 'data': {'uri': 'str', '*blk': 'bool', '*inc': 'bool', >>> - '*detach': 'bool', '*resume': 'bool' } } >>> + 'data': {'uri': 'str', '*multi-fd-uri-list': ['MigrateUriParameter'], >>> + '*blk': 'bool', '*inc': 'bool', '*detach': 'bool', >>> + '*resume': 'bool' } } >> >> Considering the existing migrate API from a QAPI design POV, I >> think there are several significant flaws with it >> >> The use of URIs is the big red flag. It is basically a data encoding >> scheme within a data encoding scheme. QEMU code should be able to >> directly work with the results from QAPI, without having todo a >> second level of parsing.
Concur. >> URIs made sense in the context of HMP or the QemuOpts CLI, but do not >> make sense in QMP. We made a mistake in this respect when we first >> introduced QMP and implemented 'migrate'. >> >> If we going to extend the migrate API I think we should stop using URIs >> for the new fields, and instead define a QAPI discriminated union for >> the different data transport backends we offer. >> >> { 'enum': 'MigrateTransport', >> 'data': ['socket', 'exec'] } >> >> { 'union': 'MigrateAddress', >> 'base': { 'transport': 'MigrateTransport'}, >> 'discriminator': 'transport', >> 'data': { >> 'socket': 'SocketAddress', >> 'exec': ['str'], >> } >> >> NB, 'socket' should be able to cover all of 'tcp', 'unix', 'vsock' >> and 'fd' already. I'm fuzzy on best way to represent RDMA. >> >> >> IIUC, the desire of migration maintainers is that we can ultimately >> have multifd as the preferred, or even only, mechanism. Aside from >> the main outbound migration control channel, and the multifd >> data channels, IIUC we have a potential desire to have more channels >> for post-copy async requests. >> >> This all suggests to me a more general representation along the >> lines of: >> >> { 'enum': 'MigrateChannelType', >> 'data': ['control', 'data', 'async'] } >> >> { 'struct': 'MigrateChannel', >> 'data': { >> 'type': 'MigrateChannelType', >> 'src-addr': 'MigrateAddress', >> 'dst-addr': 'MigrateAddress', >> 'count': 'int', >> } } >> >> { 'comand': 'migrate', >> 'data': { >> '*uri': 'str' >> '*channels': ['MigrateChannel'] >> } >> } >> >> With 'uri' and 'channels' being mutually exclusive here. >> >> This whole scheme brings in redundancy wrt to the 'migrate-set-parameters' >> API wrt multifd - essentally the same data is now being set in two >> different places. IMHO, we should declare the 'multifd' capability >> and the 'multifd-chanels' parameter deprecated, since the information >> they provide is totally redundant, if you're giving an explicit list >> of channels to 'migrate'. > > Hi Daniel. Initially while brainstorming this idea for the first time, we > also came up with the same thought of depricating the migrate > API. But how will we achieve this now and how is it going to work. Is it like > we will be making migate V2 APIs initially, integrate it and then > depricate the old one? would be happy to get some pointers from your end. Migration maintainers, please advise.