On 6/22/23 10:52, Juan Quintela wrote:
User friendliness. The problem is that if you use more than two channels with multifd, on the incoming side, you need to do:
You're sacrificing user-friendliness for the 99.99% that don't use multifd, for an error (i.e. it's not even fixing the issue) for the 0.01% that use multifd. That's not user-friendly.
- migrate_set_parameter multifd-channels 16 - migrate_incoming <uri>
The issue is not how many features the command line has, but how they're implemented.
Or if they are confusing for the user?
Anyone using multifd is not a typical user anyway.
If they're just QMP wrappers and as such they're self-contained in softmmu/vl.c, that's fine.
In fact, even for parameters, we could use keyval to parse "-incoming"
What is keyval?
util/keyval.c and include/qemu/keyval.h. It parses a list of key=value pairs into a QDict. Once you have removed the "source" key from the QDict you can use a visitor to parse the rest into a MigrateSetParameters. See the handling of QEMU_OPTION_audio, it could be something like case QEMU_OPTION_incoing: { Visitor *v; MigrateSetParameters *incoming_params = NULL; QDict *dict = keyval_parse(optarg, "source", NULL, &error_fatal); if (incoming) { if (qdict_haskey(dict, "source")) { error_setg(&error_fatal, "Parameter 'source' is duplicate"); } } else { if (!qdict_haskey(dict, "source")) { error_setg(&error_fatal, "Parameter 'source' is missing"); } runstate_set(RUN_STATE_INMIGRATE); incoming = g_strdup(qdict_get_str(dict, "source")); qdict_del(dict, "source"); } v = qobject_input_visitor_new_keyval(QOBJECT(dict)); qobject_unref(dict); visit_type_MigrateSetParameters(v, NULL, &incoming_params, &error_fatal); visit_free(v); qmp_migration_set_parameters(incoming_params, &error_fatal); qapi_free_MigrateSetParameters(incoming_params); } For example "-incoming [source=]tcp:foo,multifd-channels=16" would desugar to migrate_set_parameter multifd-channels 16 migrate_incoming tcp:foo The only incompatibility is for people who are using "," in an URI, which is rare and only an issue for the "exec" protocol. Paolo
and set the parameters in the same place as above. That would remove the need for "-global migration".
Could you elaborate?
The other option that I can think of is changing the error messages for migrate_check_parameters() and give instructions that you can't set multifd channels once that you have started incoming migration. Explaining there to use migrate_incoming command?
Later, Juan.