Re: [PATCH] multifd: Set a higher "backlog" default value for listen()

["Wang, Lei" <lei4.wang@intel.com>]

On 5/18/2023 17:16, Juan Quintela wrote:
> Lei Wang <lei4.wang@intel.com> wrote:
>> When destination VM is launched, the "backlog" parameter for listen() is set
>> to 1 as default in socket_start_incoming_migration_internal(), which will
>> lead to socket connection error (the queue of pending connections is full)
>> when "multifd" and "multifd-channels" are set later on and a high number of
>> channels are used. Set it to a hard-coded higher default value 512 to fix
>> this issue.
>>
>> Reported-by: Wei Wang <wei.w.wang@intel.com>
>> Signed-off-by: Lei Wang <lei4.wang@intel.com>
> 
> [cc'd daiel who is the maintainer of qio]
> 
> My understanding of that value is that 230 or something like that would
> be more than enough.  The maxiimum number of multifd channels is 256.

You are right, the "multifd-channels" expects uint8_t, so 256 is enough.

> 
> Daniel, any opinion?
> 
> Later, Juan.
> 
>> ---
>>  migration/socket.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/migration/socket.c b/migration/socket.c
>> index 1b6f5baefb..b43a66ef7e 100644
>> --- a/migration/socket.c
>> +++ b/migration/socket.c
>> @@ -179,7 +179,7 @@ socket_start_incoming_migration_internal(SocketAddress *saddr,
>>      QIONetListener *listener = qio_net_listener_new();
>>      MigrationIncomingState *mis = migration_incoming_get_current();
>>      size_t i;
>> -    int num = 1;
>> +    int num = 512;
>>  
>>      qio_net_listener_set_name(listener, "migration-socket-listener");
>