git: kernel - Micro optimization for vnode exclusive lock

[Matthew Dillon]

commit 221494c8053d89707ea8a45a0add00c07f5a377a
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Sat Feb 15 11:43:10 2020 -0800

    kernel - Micro optimization for vnode exclusive lock
    
    * Micro-optimize open(... O_RDWR) by allowing a shared vnode lock for
      this case when opening a file which is not an executable.
    
      We used to unconditionally get an exclusive lock to deal with VTEXT vs
      O_RDWR races against executables, but this can cause unnecessary SMP
      contention on normal files and devices opened O_RDWR which are not
      executables.

Summary of changes:
 sys/kern/vfs_cache.c    |  4 ++--
 sys/kern/vfs_nlookup.c  | 12 +++++++++---
 sys/kern/vfs_syscalls.c | 10 +++++++---
 sys/kern/vfs_vnops.c    | 20 ++++++++++++++++++--
 sys/sys/namecache.h     |  2 +-
 sys/sys/nlookup.h       |  1 +
 6 files changed, 38 insertions(+), 11 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/221494c8053d89707ea8a45a0add00c07f5a377a


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