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Diffstat (limited to 'Documentation/admin-guide/device-mapper/writecache.rst')
| -rw-r--r-- | Documentation/admin-guide/device-mapper/writecache.rst | 45 |
1 files changed, 40 insertions, 5 deletions
diff --git a/Documentation/admin-guide/device-mapper/writecache.rst b/Documentation/admin-guide/device-mapper/writecache.rst index d3d7690f5e8d..60c16b7fd5ac 100644 --- a/Documentation/admin-guide/device-mapper/writecache.rst +++ b/Documentation/admin-guide/device-mapper/writecache.rst @@ -12,7 +12,6 @@ first sector should contain valid superblock from previous invocation. Constructor parameters: 1. type of the cache device - "p" or "s" - - p - persistent memory - s - SSD 2. the underlying device that will be cached @@ -37,10 +36,10 @@ Constructor parameters: autocommit_blocks n (default: 64 for pmem, 65536 for ssd) when the application writes this amount of blocks without issuing the FLUSH request, the blocks are automatically - commited + committed autocommit_time ms (default: 1000) autocommit time in milliseconds. The data is automatically - commited if this time passes and no FLUSH request is + committed if this time passes and no FLUSH request is received fua (by default on) applicable only to persistent memory - use the FUA flag @@ -53,19 +52,51 @@ Constructor parameters: - some underlying devices perform better with fua, some with nofua. The user should test it + cleaner + when this option is activated (either in the constructor + arguments or by a message), the cache will not promote + new writes (however, writes to already cached blocks are + promoted, to avoid data corruption due to misordered + writes) and it will gradually writeback any cached + data. The userspace can then monitor the cleaning + process with "dmsetup status". When the number of cached + blocks drops to zero, userspace can unload the + dm-writecache target and replace it with dm-linear or + other targets. + max_age n + specifies the maximum age of a block in milliseconds. If + a block is stored in the cache for too long, it will be + written to the underlying device and cleaned up. + metadata_only + only metadata is promoted to the cache. This option + improves performance for heavier REQ_META workloads. + pause_writeback n (default: 3000) + pause writeback if there was some write I/O redirected to + the origin volume in the last n milliseconds Status: + 1. error indicator - 0 if there was no error, otherwise error number 2. the number of blocks 3. the number of free blocks 4. the number of blocks under writeback +5. the number of read blocks +6. the number of read blocks that hit the cache +7. the number of write blocks +8. the number of write blocks that hit uncommitted block +9. the number of write blocks that hit committed block +10. the number of write blocks that bypass the cache +11. the number of write blocks that are allocated in the cache +12. the number of write requests that are blocked on the freelist +13. the number of flush requests +14. the number of discarded blocks Messages: flush - flush the cache device. The message returns successfully + Flush the cache device. The message returns successfully if the cache device was flushed without an error flush_on_suspend - flush the cache device on next suspend. Use this message + Flush the cache device on next suspend. Use this message when you are going to remove the cache device. The proper sequence for removing the cache device is: @@ -77,3 +108,7 @@ Messages: 5. resume the device, so that it will use the linear target 6. the cache device is now inactive and it can be deleted + cleaner + See above "cleaner" constructor documentation. + clear_stats + Clear the statistics that are reported on the status line |