"Wang, Wei W" <wei.w.w...@intel.com> wrote: > On Friday, May 19, 2023 9:31 AM, Wang, Lei4 wrote: >> On 5/18/2023 17:16, Juan Quintela wrote: >> > Lei Wang <lei4.w...@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.w...@intel.com> >> >> Signed-off-by: Lei Wang <lei4.w...@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. >> > > We can change it to uint16_t or uint32_t, but need to see if listening on a > larger > value is OK to everyone.
If we need something more than 256 channels for migration, we ar edoing something really weird. We can saturate a 100Gigabit network relatively easily with 10 channels. 256 Channels would mean that we have at least 2TBit/s networking. I am not expecting that really soon. And as soon as that happens I would expect CPU's to handle easily more that 10Gigabits/second. > Man page of listen mentions that the maximum length of the queue for > incomplete sockets can be set using /proc/sys/net/ipv4/tcp_max_syn_backlog, > and it is 4096 by default on my machine. I think that current code is ok. We just need to enforce that we use defer. Later, Juan.
