cvs commit: src/sys/netinet in_pcb.h udp_usrreq.c

[Robert Watson]

rwatson     2008-07-15 15:38:47 UTC

  FreeBSD src repository

  Modified files:
    sys/netinet          in_pcb.h udp_usrreq.c 
  Log:
  SVN rev 180536 on 2008-07-15 15:38:47Z by rwatson
  
  Merge last of a series of rwlock conversion changes to UDP, which
  completes the move to a fully parallel UDP transmit path by using
  global read, rather than write, locking of inpcbinfo in further
  semi-connected cases:
  
  - Add macros to allow try-locking of inpcb and inpcbinfo.
  - Always acquire an incpcb read lock in udp_output(), which stablizes the
    local inpcb address and port bindings in order to determine what further
    locking is required:
    - If the inpcb is currently not bound (at all) and are implicitly
      connecting, we require inpcbinfo and inpcb write locks, so drop the
      read lock and re-acquire.
    - If the inpcb is bound for at least one of the port or address, but an
      explicit source or destination is requested, trylock the inpcbinfo
      lock, and if that fails, drop the inpcb lock, lock the global lock,
      and relock the inpcb lock.
    - Otherwise, no further locking is required (common case).
  - Update comments.
  
  In practice, this means that the vast majority of consumers of UDP sockets
  will not acquire any exclusive locks at the socket or UDP levels of the
  network stack.  This leads to a marked performance improvement in several
  important workloads, including BIND, nsd, and memcached over UDP, as well
  as significant improvements in pps microbenchmarks.
  
  The plan is to MFC all of the rwlock changes to RELENG_7 once they have
  settled for a weeks in the tree.
  
  Tested by:      ps, kris (older revision), bde
  MFC after:      3 weeks
  
  Revision  Changes    Path
  1.110     +4 -0      src/sys/netinet/in_pcb.h
  1.231     +85 -34    src/sys/netinet/udp_usrreq.c