cvs commit: src/sys/net bpf.c bpf_zerocopy.c bpf_zerocopy.h src/share/man/man4 bpf.4

[Robert Watson]

rwatson     2008-04-07 02:51:00 UTC

  FreeBSD src repository

  Modified files:
    sys/net              bpf.c bpf_zerocopy.c bpf_zerocopy.h 
    share/man/man4       bpf.4 
  Log:
  Maintain and observe a ZBUF_FLAG_IMMUTABLE flag on zero-copy BPF
  buffer kernel descriptors, which is used to allow the buffer
  currently in the BPF "store" position to be assigned to userspace
  when it fills, even if userspace hasn't acknowledged the buffer
  in the "hold" position yet.  To implement this, notify the buffer
  model when a buffer becomes full, and check that the store buffer
  is writable, not just for it being full, before trying to append
  new packet data.  Shared memory buffers will be assigned to
  userspace at most once per fill, be it in the store or in the
  hold position.
  
  This removes the restriction that at most one shared memory can
  by owned by userspace, reducing the chances that userspace will
  need to call select() after acknowledging one buffer in order to
  wait for the next buffer when under high load.  This more fully
  realizes the goal of zero system calls in order to process a
  high-speed packet stream from BPF.
  
  Update bpf.4 to reflect that both buffers may be owned by userspace
  at once; caution against assuming this.
  
  Revision  Changes    Path
  1.50      +8 -8      src/share/man/man4/bpf.4
  1.191     +50 -10    src/sys/net/bpf.c
  1.4       +73 -4     src/sys/net/bpf_zerocopy.c
  1.2       +2 -0      src/sys/net/bpf_zerocopy.h