On 5/19/2023 10:44, Wang, Wei W 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.
Is there any use case to use >256 migration channels? If not, then I suppose it's no need to increase it. > > 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
