> On Jul 17, 2019, at 1:19 PM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > On Wed, 2019-07-17 at 09:55 -0400, Chuck Lever wrote: >> Hi Trond- >> >>> On Jul 16, 2019, at 4:01 PM, Trond Myklebust <trondmy@xxxxxxxxx> >>> wrote: >>> >>> Add a per-transport maximum limit in the socket case, and add >>> helpers to allow the NFSv4 code to discover that limit. >> >> For RDMA, the number of credits is permitted to change during the >> life >> of the connection, so this is not a fixed limit for such transports. > > This is defining a maximum value, which is used for backchannel session > slot negotiation. > >> >> And, AFAICT, it's not necessary to know the transport's limit. The >> lesser of the NFS backchannel and RPC/RDMA reverse credit limit will >> be used. > > The server needs to know how many requests it can send in parallel on > the back channel. If it sends too many, which it can and will do on > TCP, then we currently break the connection, and so callbacks end up > being dropped or missed altogether. IIUC, RPC/RDMA has a fixed maximum constant. Would you like a patch at some point that advertises that constant via ->bc_num_slots ? -- Chuck Lever
