git: VN - Remove use of IO_DIRECT, Improve lock performance for reads

[Matthew Dillon]

commit b527c4c540cc186db2c8aa7105d074135e7b8ea5
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Tue Mar 2 23:15:27 2010 -0800

    VN - Remove use of IO_DIRECT, Improve lock performance for reads
    
    * Remove the use of IO_DIRECT.  This just doesn't work very well,
      particularly when the device backing the VN has a different logical
      block size than the device using VN.
    
      This will result in heavier use of the buffer cache and more
      (temporarily) duplicated data, but also has much better performance.
    
    * Use LK_SHARED for VOP_READ()s instead of LK_EXCLUSIVE, which allows
      concurrent reads to be issued.
    
    Reported-by: Vincent Stemen <vince.dragonfly at hightek.org>

Summary of changes:
 sys/dev/disk/vn/vn.c |   21 ++++++++++++++++-----
 1 files changed, 16 insertions(+), 5 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/b527c4c540cc186db2c8aa7105d074135e7b8ea5


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