Some IO scheduler cleanup in Documentation/block
as-iosched.txt:
o Changed IO scheduler selection text to a reference to the
switching-sched.txt file.
o Fixed typo: 'for up time...' -> 'for up to...'
o Added short description of the est_time file.
deadline-iosched.txt:
o Changed IO scheduler selection text to a reference to the
switching-sched.txt file.
o Removed references to non-existent seek-cost and stream_unit.
o Fixed typo: 'write_starved' -> 'writes_starved'
switching-sched.txt:
o Added in boot-time argument to set the default IO scheduler. (From
as-iosched.txt)
o Added in sysfs mount instructions. (From deadline-iosched.txt)
Signed-off-by: Alan D. Brunelle <Alan.Brunelle@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/Documentation/block/deadline-iosched.txt b/Documentation/block/deadline-iosched.txt
index 03775dd..c23cab1 100644
--- a/Documentation/block/deadline-iosched.txt
+++ b/Documentation/block/deadline-iosched.txt
@@ -5,16 +5,10 @@
In particular, it will clarify the meaning of the exposed tunables that may be
of interest to power users.
-Each io queue has a set of io scheduler tunables associated with it. These
-tunables control how the io scheduler works. You can find these entries
-in:
-
-/sys/block/<device>/queue/iosched
-
-assuming that you have sysfs mounted on /sys. If you don't have sysfs mounted,
-you can do so by typing:
-
-# mount none /sys -t sysfs
+Selecting IO schedulers
+-----------------------
+Refer to Documentation/block/switching-sched.txt for information on
+selecting an io scheduler on a per-device basis.
********************************************************************************
@@ -41,14 +35,11 @@
When a read request expires its deadline, we must move some requests from
the sorted io scheduler list to the block device dispatch queue. fifo_batch
-controls how many requests we move, based on the cost of each request. A
-request is either qualified as a seek or a stream. The io scheduler knows
-the last request that was serviced by the drive (or will be serviced right
-before this one). See seek_cost and stream_unit.
+controls how many requests we move.
-write_starved (number of dispatches)
--------------
+writes_starved (number of dispatches)
+--------------
When we have to move requests from the io scheduler queue to the block
device dispatch queue, we always give a preference to reads. However, we