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authorLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 10:09:16 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 10:09:16 -0700
commit92d15c2ccbb3e31a3fc71ad28fdb55e1319383c0 (patch)
tree8d83c0dc3c6b935d8367e331872f242b742f0a8a /Documentation/block/deadline-iosched.txt
parentf20bf6125605acbbc7eb8c9420d7221c91aa83eb (diff)
parent644bd2f048972d75eb1979b1fdca257d528ce687 (diff)
Merge branch 'for-linus' of git://git.kernel.dk/data/git/linux-2.6-block
* 'for-linus' of git://git.kernel.dk/data/git/linux-2.6-block: (63 commits) Fix memory leak in dm-crypt SPARC64: sg chaining support SPARC: sg chaining support PPC: sg chaining support PS3: sg chaining support IA64: sg chaining support x86-64: enable sg chaining x86-64: update pci-gart iommu to sg helpers x86-64: update nommu to sg helpers x86-64: update calgary iommu to sg helpers swiotlb: sg chaining support i386: enable sg chaining i386 dma_map_sg: convert to using sg helpers mmc: need to zero sglist on init Panic in blk_rq_map_sg() from CCISS driver remove sglist_len remove blk_queue_max_phys_segments in libata revert sg segment size ifdefs Fixup u14-34f ENABLE_SG_CHAINING qla1280: enable use_sg_chaining option ...
Diffstat (limited to 'Documentation/block/deadline-iosched.txt')
-rw-r--r--Documentation/block/deadline-iosched.txt25
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>