cvs commit: src/sys/i386/i386 vm_machdep.c src/sys/i386/include sf_buf.h

[Alan Cox]

alc         2003/12/07 14:49:25 PST

  FreeBSD src repository

  Modified files:
    sys/i386/i386        vm_machdep.c 
    sys/i386/include     sf_buf.h 
  Log:
  Don't remove the virtual-to-physical mapping when an sf_buf is freed.
  Instead, allow the mapping to persist, but add the sf_buf to a free list.
  If a later sendfile(2) or zero-copy send resends the same physical page,
  perhaps with the same or different contents, then the mapping overhead is
  avoided and the sf_buf is simply removed from the free list.
  
  In other words, the i386 sf_buf implementation now behaves as a cache of
  virtual-to-physical translations using an LRU replacement policy on
  inactive sf_bufs.  This is similar in concept to a part of
  http://www.cs.princeton.edu/~yruan/debox/ patch, but much simpler in
  implementation.  Note: none of this is required on alpha, amd64, or ia64.
  They now use their direct virtual-to-physical mapping to avoid any
  emphemeral mapping overheads in their sf_buf implementations.
  
  Revision  Changes    Path
  1.220     +10 -9     src/sys/i386/i386/vm_machdep.c
  1.3       +1 -0      src/sys/i386/include/sf_buf.h