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| -rw-r--r-- | Documentation/device-mapper/dm-service-time.rst (renamed from Documentation/device-mapper/dm-service-time.txt) | 76 |
1 files changed, 43 insertions, 33 deletions
diff --git a/Documentation/device-mapper/dm-service-time.txt b/Documentation/device-mapper/dm-service-time.rst index fb1d4a0cf122..facf277fc13c 100644 --- a/Documentation/device-mapper/dm-service-time.txt +++ b/Documentation/device-mapper/dm-service-time.rst @@ -1,3 +1,4 @@ +=============== dm-service-time =============== @@ -12,25 +13,34 @@ in a path-group, and it can be specified as a table argument. The path selector name is 'service-time'. -Table parameters for each path: [<repeat_count> [<relative_throughput>]] - <repeat_count>: The number of I/Os to dispatch using the selected +Table parameters for each path: + + [<repeat_count> [<relative_throughput>]] + <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. - <relative_throughput>: The relative throughput value of the path + <relative_throughput>: + The relative throughput value of the path among all paths in the path-group. The valid range is 0-100. If not given, minimum value '1' is used. If '0' is given, the path isn't selected while other paths having a positive value are available. -Status for each path: <status> <fail-count> <in-flight-size> \ - <relative_throughput> - <status>: 'A' if the path is active, 'F' if the path is failed. - <fail-count>: The number of path failures. - <in-flight-size>: The size of in-flight I/Os on the path. - <relative_throughput>: The relative throughput value of the path - among all paths in the path-group. +Status for each path: + + <status> <fail-count> <in-flight-size> <relative_throughput> + <status>: + 'A' if the path is active, 'F' if the path is failed. + <fail-count>: + The number of path failures. + <in-flight-size>: + The size of in-flight I/Os on the path. + <relative_throughput>: + The relative throughput value of the path + among all paths in the path-group. Algorithm @@ -39,7 +49,7 @@ Algorithm dm-service-time adds the I/O size to 'in-flight-size' when the I/O is dispatched and subtracts when completed. Basically, dm-service-time selects a path having minimum service time -which is calculated by: +which is calculated by:: ('in-flight-size' + 'size-of-incoming-io') / 'relative_throughput' @@ -67,25 +77,25 @@ Examples ======== In case that 2 paths (sda and sdb) are used with repeat_count == 128 and sda has an average throughput 1GB/s and sdb has 4GB/s, -'relative_throughput' value may be '1' for sda and '4' for sdb. - -# echo "0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 1 8:16 128 4" \ - dmsetup create test -# -# dmsetup table -test: 0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 1 8:16 128 4 -# -# dmsetup status -test: 0 10 multipath 2 0 0 0 1 1 E 0 2 2 8:0 A 0 0 1 8:16 A 0 0 4 - - -Or '2' for sda and '8' for sdb would be also true. - -# echo "0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 2 8:16 128 8" \ - dmsetup create test -# -# dmsetup table -test: 0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 2 8:16 128 8 -# -# dmsetup status -test: 0 10 multipath 2 0 0 0 1 1 E 0 2 2 8:0 A 0 0 2 8:16 A 0 0 8 +'relative_throughput' value may be '1' for sda and '4' for sdb:: + + # echo "0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 1 8:16 128 4" \ + dmsetup create test + # + # dmsetup table + test: 0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 1 8:16 128 4 + # + # dmsetup status + test: 0 10 multipath 2 0 0 0 1 1 E 0 2 2 8:0 A 0 0 1 8:16 A 0 0 4 + + +Or '2' for sda and '8' for sdb would be also true:: + + # echo "0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 2 8:16 128 8" \ + dmsetup create test + # + # dmsetup table + test: 0 10 multipath 0 0 1 1 service-time 0 2 2 8:0 128 2 8:16 128 8 + # + # dmsetup status + test: 0 10 multipath 2 0 0 0 1 1 E 0 2 2 8:0 A 0 0 2 8:16 A 0 0 8 |