diff options
author | Ingo Molnar <mingo@elte.hu> | 2009-09-07 08:19:51 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2009-09-07 08:19:51 +0200 |
commit | a1922ed661ab2c1637d0b10cde933bd9cd33d965 (patch) | |
tree | 0f1777542b385ebefd30b3586d830fd8ed6fda5b /Documentation/device-mapper/dm-queue-length.txt | |
parent | 75e33751ca8bbb72dd6f1a74d2810ddc8cbe4bdf (diff) | |
parent | d28daf923ac5e4a0d7cecebae56f3e339189366b (diff) |
Merge branch 'tracing/core' into tracing/hw-breakpoints
Conflicts:
arch/Kconfig
kernel/trace/trace.h
Merge reason: resolve the conflicts, plus adopt to the new
ring-buffer APIs.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/device-mapper/dm-queue-length.txt')
-rw-r--r-- | Documentation/device-mapper/dm-queue-length.txt | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/device-mapper/dm-queue-length.txt b/Documentation/device-mapper/dm-queue-length.txt new file mode 100644 index 00000000000..f4db2562175 --- /dev/null +++ b/Documentation/device-mapper/dm-queue-length.txt @@ -0,0 +1,39 @@ +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 |