git: bioqdisksort - fixes to avoid starvation

[Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxxxxx>]

commit 539f339ee934d4f0a53b0071fb42acc78b49269b
Author: Matthew Dillon <dillon@apollo.backplane.com>
Date:   Sat Aug 8 15:07:40 2009 -0700

    bioqdisksort - fixes to avoid starvation
    
    Long chains of pipelined write I/O were being sorted in front of other
    requests.  Due to the pipelining these other requests would wind up
    getting starved virtually permanently.
    
    Prevent starvation by forcing one out of every 16 BIOs to be ordered.
    
    This fixes issues with HAMMER which tends to have more of an absolute
    ordering of meta data verses data then UFS.

Summary of changes:
 sys/kern/subr_disk.c |   14 +++++++++++++-
 sys/sys/buf.h        |    1 +
 sys/sys/buf2.h       |   13 +++++++++++--
 3 files changed, 25 insertions(+), 3 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/539f339ee934d4f0a53b0071fb42acc78b49269b


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