diff options
Diffstat (limited to 'Documentation/block/deadline-iosched.txt')
| -rw-r--r-- | Documentation/block/deadline-iosched.txt | 25 |
1 files changed, 8 insertions, 17 deletions
diff --git a/Documentation/block/deadline-iosched.txt b/Documentation/block/deadline-iosched.txt index be08ffd1e9b..c23cab13c3d 100644 --- a/Documentation/block/deadline-iosched.txt +++ b/Documentation/block/deadline-iosched.txt @@ -5,16 +5,10 @@ This little file attempts to document how the deadline io scheduler works. 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 @@ fifo_batch 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 @@ -73,6 +64,6 @@ that comes at basically 0 cost we leave that on. We simply disable the rbtree front sector lookup when the io scheduler merge function is called. -Nov 11 2002, Jens Axboe <axboe@suse.de> +Nov 11 2002, Jens Axboe <jens.axboe@oracle.com> |