git: dsched - Add request polling wrapper

[Alex Hornung]

commit 09f2bfe9d39a346abddc196cafc213e571044dfb
Author: Brills Peng <brills at gmail.com>
Date:   Sat Aug 27 11:24:35 2011 +0000

    dsched - Add request polling wrapper
    
     * Add a request polling emulation layer to dsched. This emulated
       request polling as if a disk driver would poll for requests instead
       of requests being actively pushed down.
    
     * The policy->polling_func() callback is called whenever a BIO
       completes.
    
     * A field in the diskctx that shows the current tag queue depth and the
       maximum tag queue depth (currently fixed value of 32) are used in the
       policies using request polling directly and is not enforced in the
       dsched layer. That is, a policy using request polling emulation
       should take care of not having (many) more BIOs in flight than
       max_tag_queue_depth.
    
    Sponsored-by: Google Summer of Code

Summary of changes:
 sys/kern/kern_dsched.c |   69 ++++++++++++++++++++++++++++++++++++++++++++++++
 sys/sys/dsched.h       |   11 +++++++-
 2 files changed, 79 insertions(+), 1 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/09f2bfe9d39a346abddc196cafc213e571044dfb


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