Merge branch 'for-2.6.34' of git://git.kernel.dk/linux-2.6-block

[linux-2.6.git] / Documentation / ABI / testing / sysfs-block

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index d2f90334bb93f90af2986e96d3cfd9710180eca7..4873c759d535a7549d5eecf62a7125b29d6c2dea 100644 (file)
--- 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.