linux/Documentation/block
Tejun Heo d02f7aa8dc cfq-iosched: enable full blkcg hierarchy support
With the previous two patches, all cfqg scheduling decisions are based
on vfraction and ready for hierarchy support.  The only thing which
keeps the behavior flat is cfqg_flat_parent() which makes vfraction
calculation consider all non-root cfqgs children of the root cfqg.

Replace it with cfqg_parent() which returns the real parent.  This
enables full blkcg hierarchy support for cfq-iosched.  For example,
consider the following hierarchy.

        root
      /      \
   A:500      B:250
  /     \
 AA:500  AB:1000

For simplicity, let's say all the leaf nodes have active tasks and are
on service tree.  For each leaf node, vfraction would be

 AA: (500  / 1500) * (500 / 750) =~ 0.2222
 AB: (1000 / 1500) * (500 / 750) =~ 0.4444
  B:                 (250 / 750) =~ 0.3333

and vdisktime will be distributed accordingly.  For more detail,
please refer to Documentation/block/cfq-iosched.txt.

v2: cfq-iosched.txt updated to describe group scheduling as suggested
    by Vivek.

v3: blkio-controller.txt updated.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
2013-01-09 08:05:11 -08:00
..
00-INDEX Documentation: update missing index files in block/00-INDEX 2012-08-09 15:27:28 +02:00
biodoc.txt block: Kill bi_destructor 2012-09-09 10:35:39 +02:00
capability.txt genhd: expose AN to user space 2007-05-23 20:14:11 -07:00
cfq-iosched.txt cfq-iosched: enable full blkcg hierarchy support 2013-01-09 08:05:11 -08:00
data-integrity.txt Trivial typo fixes in Documentation/block/data-integrity.txt. 2009-07-01 10:56:25 +02:00
deadline-iosched.txt trivial: Miscellaneous documentation typo fixes 2009-06-12 18:01:47 +02:00
ioprio.txt Update Jens Axboe's email in Documentation/* 2007-10-16 09:59:55 +02:00
queue-sysfs.txt Documentation: update tunable options in block/cfq-iosched.txt 2012-08-09 15:28:05 +02:00
request.txt Update Jens Axboe's email in Documentation/* 2007-10-16 09:59:55 +02:00
stat.txt [PATCH] block/stat.txt 2006-01-08 20:14:01 -08:00
switching-sched.txt Documentation: drop as block elevator reference in switching-sched.txt 2011-11-04 12:01:48 -07:00
writeback_cache_control.txt block: update documentation for REQ_FLUSH / REQ_FUA 2010-09-10 12:35:37 +02:00