summaryrefslogtreecommitdiffstats
path: root/Documentation/admin-guide/device-mapper/dm-queue-length.rst
diff options
context:
space:
mode:
authorRosen Penev <rosenp@gmail.com>2026-09-27 13:35:01 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2026-10-01 11:04:53 +0200
commit8167c1f071426706c233e93ecfd13aba7d5c06c8 (patch)
tree2c0cd5f5e1cc35eadee98d49fe034f96a88856ce /Documentation/admin-guide/device-mapper/dm-queue-length.rst
downloadlinux-stable-8167c1f071426706c233e93ecfd13aba7d5c06c8.tar.gz
linux-stable-8167c1f071426706c233e93ecfd13aba7d5c06c8.zip
tty: serial: mpc52xx_uart: move static declarations up.grafted
Avoid a compilation error so that they're not used before being declared. Fixes: 4d105880666a ("tty: serial: mpc52xx_uart: add bounds check for psc_num array index") Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202609260356.tJWbd1WU-lkp@intel.com/ Signed-off-by: Rosen Penev <rosenp@gmail.com> Link: https://patch.msgid.link/20260927203501.14105-1-rosenp@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/admin-guide/device-mapper/dm-queue-length.rst')
-rw-r--r--Documentation/admin-guide/device-mapper/dm-queue-length.rst48
1 files changed, 48 insertions, 0 deletions
diff --git a/Documentation/admin-guide/device-mapper/dm-queue-length.rst b/Documentation/admin-guide/device-mapper/dm-queue-length.rst
new file mode 100644
index 000000000..d8e381c1c
--- /dev/null
+++ b/Documentation/admin-guide/device-mapper/dm-queue-length.rst
@@ -0,0 +1,48 @@
+===============
+dm-queue-length
+===============
+
+dm-queue-length is a path selector module for device-mapper targets,
+which selects a path with the least number of in-flight I/Os.
+The path selector name is 'queue-length'.
+
+Table parameters for each path: [<repeat_count>]
+
+::
+
+ <repeat_count>: The number of I/Os to dispatch using the selected
+ path before switching to the next path.
+ If not given, internal default is used. To check
+ the default value, see the activated table.
+
+Status for each path: <status> <fail-count> <in-flight>
+
+::
+
+ <status>: 'A' if the path is active, 'F' if the path is failed.
+ <fail-count>: The number of path failures.
+ <in-flight>: The number of in-flight I/Os on the path.
+
+
+Algorithm
+=========
+
+dm-queue-length increments/decrements 'in-flight' when an I/O is
+dispatched/completed respectively.
+dm-queue-length selects a path with the minimum 'in-flight'.
+
+
+Examples
+========
+In case that 2 paths (sda and sdb) are used with repeat_count == 128.
+
+::
+
+ # echo "0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128" \
+ dmsetup create test
+ #
+ # dmsetup table
+ test: 0 10 multipath 0 0 1 1 queue-length 0 2 1 8:0 128 8:16 128
+ #
+ # dmsetup status
+ test: 0 10 multipath 2 0 0 0 1 1 E 0 2 1 8:0 A 0 0 8:16 A 0 0