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authorLinus Torvalds <torvalds@linux-foundation.org>2010-03-01 09:00:29 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-01 09:00:29 -0800
commitb1bf9368407ae7e89d8a005bb40beb70a41df539 (patch)
tree3815c8aab19c6c186736673c624fef5f3faab716 /Documentation
parent524df55725217b13d5a232fb5badb5846418ea0e (diff)
parent4671a1322052425afa38fcb7980d2fd2bb0fc99b (diff)
downloadblackbird-op-linux-b1bf9368407ae7e89d8a005bb40beb70a41df539.tar.gz
blackbird-op-linux-b1bf9368407ae7e89d8a005bb40beb70a41df539.zip
Merge branch 'for-2.6.34' of git://git.kernel.dk/linux-2.6-block
* 'for-2.6.34' of git://git.kernel.dk/linux-2.6-block: (38 commits) block: don't access jiffies when initialising io_context cfq: remove 8 bytes of padding from cfq_rb_root on 64 bit builds block: fix for "Consolidate phys_segment and hw_segment limits" cfq-iosched: quantum check tweak blktrace: perform cleanup after setup error blkdev: fix merge_bvec_fn return value checks cfq-iosched: requests "in flight" vs "in driver" clarification cciss: Fix problem with scatter gather elements in the scsi half of the driver cciss: eliminate unnecessary pointer use in cciss scsi code cciss: do not use void pointer for scsi hba data cciss: factor out scatter gather chain block mapping code cciss: fix scatter gather chain block dma direction kludge cciss: simplify scatter gather code cciss: factor out scatter gather chain block allocation and freeing cciss: detect bad alignment of scsi commands at build time cciss: clarify command list padding calculation cfq-iosched: rethink seeky detection for SSDs cfq-iosched: rework seeky detection block: remove padding from io_context on 64bit builds block: Consolidate phys_segment and hw_segment limits ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-block14
-rw-r--r--Documentation/block/queue-sysfs.txt10
2 files changed, 19 insertions, 5 deletions
diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index d2f90334bb93..4873c759d535 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -128,3 +128,17 @@ Description:
preferred request size for workloads where sustained
throughput is desired. If no optimal I/O size is
reported this file contains 0.
+
+What: /sys/block/<disk>/queue/nomerges
+Date: January 2010
+Contact:
+Description:
+ Standard I/O elevator operations include attempts to
+ merge contiguous I/Os. For known random I/O loads these
+ attempts will always fail and result in extra cycles
+ being spent in the kernel. This allows one to turn off
+ this behavior on one of two ways: When set to 1, complex
+ merge checks are disabled, but the simple one-shot merges
+ with the previous I/O request are enabled. When set to 2,
+ all merge tries are disabled. The default value is 0 -
+ which enables all types of merge tries.
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index e164403f60e1..f65274081c8d 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -25,11 +25,11 @@ size allowed by the hardware.
nomerges (RW)
-------------
-This enables the user to disable the lookup logic involved with IO merging
-requests in the block layer. Merging may still occur through a direct
-1-hit cache, since that comes for (almost) free. The IO scheduler will not
-waste cycles doing tree/hash lookups for merges if nomerges is 1. Defaults
-to 0, enabling all merges.
+This enables the user to disable the lookup logic involved with IO
+merging requests in the block layer. By default (0) all merges are
+enabled. When set to 1 only simple one-hit merges will be tried. When
+set to 2 no merge algorithms will be tried (including one-hit or more
+complex tree/hash lookups).
nr_requests (RW)
----------------
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