47eb5abfab
Increase NFS_MAXRAHEAD to 32. With 32k read or write requests, that amounts to 1 Mbyte of read-ahead, enough to cover about 10 ms latency at gigabit Ethernet speeds. Increase the table of nfsiod kthreads (NFS_MAXASYNCDAEMON) from 20 to 128, to match the raised value of NFS_MAXRAHEAD. (Making the limit dynamic requires replacing the compile-time array with a dynamic structure.) Add a comment explaining that each read-ahead requires an I/O thread. Wrap both parameters with an #ifdef <parameter>/#endif, to allow hand-tuned values or (later) a kernel config-file option override.