Product Feature - Unix Cache Manager Large File Performance Improvements

With v0.189 a 1TB file copy on Linux using 'dd' took 3.7 hours to copy to /afs whereas with v0.188 it took 11 hours.

  dd if=/dev/zero bs=1M, cache size: 2G
  dcaches: 50000, chunk size: 256K

During the v0.188 copy there were 288 soft lockup events reported whereas with v0.189 there were none.

  [157841.618236] watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [dd:959736]
  [157841.618291] RIP: 0010:afs_StoreAllSegments+0x407/0xd20 [yfs]

A soft lockup event is reported when a task is running on a CPU for a period of time longer than the configured 'watchdog_thresh' period. If a task takes too long to execute the nmi-watchdog task responsible for the CPU does not execute. In this case the afs_StoreAllSegments task is executing an algorithm whose run time is dependent upon the file size.