Commit 8a81f16de64f ("NFSD: Add a "default" block size") introduced NFSSVC_DEFBLKSIZE at 1MB, well below the 4MB NFSSVC_MAXBLKSIZE ceiling, with the stated intent that a later change would raise the default. Raising the default reduces per-RPC overhead on fast networks by amortizing header processing and scheduling costs across larger payloads. The halving loop in nfsd_get_default_max_blksize() constrains the returned value to 1/4096 of available RAM, so the new 4MB default takes effect only on systems with at least 16GB of RAM. Smaller machines continue to receive the same computed value as before. Administrators can still override the computed value through /proc/fs/nfsd/max_block_size. On systems where the new default takes effect, svc_sock_setbufsize() sizes each service socket's send and receive buffers as nreqs * max_mesg * 2. Quadrupling max_mesg therefore quadruples the per-socket buffer reservation at a fixed thread count, which operators tuning large thread pools should account for. Note well: Your NFS client implementation must support large read and write size settings to benefit from this change. Reviewed-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Roland Mainz <roland.mainz@nrubsig.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>