v6.5.4 rocksdb.*cf: supply descriptions on ttl and `periodic-compac…

…tion-seconds`. (#13980) (#15131)

releases/release-6.5.4.md

@@ -14,6 +14,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v6.5/quick-start-with-
 ## Compatibility changes
 
 - To fix the issue that TiDB consumes too much memory when using `Cursor Fetch` to fetch a large result set, TiDB automatically writes the result set to the disk to release memory [#43233](https://github.com/pingcap/tidb/issues/43233) @[YangKeao](https://github.com/YangKeao)
+- Disable periodic compaction of RocksDB by default, so that the default behavior of TiKV RocksDB is now consistent with that in versions before v6.5.0. This change prevents potential performance impact caused by a significant number of compactions after upgrading. In addition, TiKV introduces two new configuration items [`rocksdb.[defaultcf|writecf|lockcf].periodic-compaction-seconds`](/tikv-configuration-file.md#periodic-compaction-seconds-new-in-v654) and [`rocksdb.[defaultcf|writecf|lockcf].ttl`](/tikv-configuration-file.md#ttl-new-in-v654), enabling you to manually configure periodic compaction of RocksDB [#15355](https://github.com/tikv/tikv/issues/15355) @[LykxSassinator](https://github.com/LykxSassinator)
 
 ## Improvements
 

tikv-configuration-file.md

@@ -1496,6 +1496,18 @@ Configuration items related to `rocksdb.defaultcf`, `rocksdb.writecf`, and `rock
     - `5`: Can be read by TiKV v6.1 and later versions. Full and partitioned filters use a faster and more accurate Bloom filter implementation with a different schema.
 + Default value: `2`
 
+### `ttl` <span class="version-mark">New in v6.5.4</span>
+
++ SST files with updates older than the TTL will be automatically selected for compaction. These SST files will go through the compaction in a cascading way so that they can be compacted to the bottommost level or file.
++ Default value: `"0s"`, meaning that no SST file is selected by default.
++ Unit: s(second)|h(hour)|d(day)
+
+### `periodic-compaction-seconds` <span class="version-mark">New in v6.5.4</span>
+
++ The time interval for periodic compaction. SST files with updates older than this value will be selected for compaction and rewritten to the same level where these SST files originally reside.
++ Default value: `"0s"`, meaning that periodic compaction is disabled by default.
++ Unit: s(second)|h(hour)|d(day)
+
 ## rocksdb.defaultcf.titan
 
 Configuration items related to `rocksdb.defaultcf.titan`.