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.
