tikv-configuration-file: update flow-control override behavior for v8.5.5 #21244

hhwyt · 2026-01-07T09:10:14Z

What is changed, added or deleted? (Required)

Update documentation for storage.flow-control.l0-files-threshold and storage.flow-control.soft-pending-compaction-bytes-limit to reflect the behavior change introduced in TiKV PR #18994.

v8.5.4 and earlier: flow-control config unconditionally overrides the corresponding RocksDB config.
From v8.5.5: flow-control config only overrides when it is smaller than the RocksDB config, to avoid weakening RocksDB's compaction acceleration mechanism when increasing flow-control thresholds.

Also update the corresponding RocksDB config items (level0-slowdown-writes-trigger, soft-pending-compaction-bytes-limit) with the same version-specific behavior notes.

Which TiDB version(s) do your changes apply to? (Required)

What is the related PR or file link(s)?

Related TiKV PR: flow-control: fix compaction slowdown caused by increased flow-control thresholds. (#18710) tikv/tikv#18994

Do your changes match any of the following descriptions?

Delete files
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Might cause conflicts after applied to another branch

….5.5 Update documentation for storage.flow-control.l0-files-threshold and storage.flow-control.soft-pending-compaction-bytes-limit to reflect the behavior change introduced in TiKV PR pingcap#18994. - v8.5.4 and earlier: flow-control config unconditionally overrides the corresponding RocksDB config. - From v8.5.5: flow-control config only overrides when it is smaller than the RocksDB config, to avoid weakening RocksDB's compaction acceleration mechanism when increasing flow-control thresholds. Also update the corresponding RocksDB config items (level0-slowdown-writes-trigger, soft-pending-compaction-bytes-limit) with the same version-specific behavior notes.

ti-chi-bot · 2026-01-07T09:10:24Z

Hi @hhwyt. Thanks for your PR.

I'm waiting for a pingcap member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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hhwyt · 2026-01-07T09:26:33Z

/cc @qiancai @hbisheng PTAL, thx~

qiancai · 2026-01-07T09:28:22Z

/ok-to-test

ti-chi-bot · 2026-01-07T09:47:32Z

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qiancai · 2026-01-09T02:41:04Z

tikv-configuration-file.md

+ v8.5.4 及之前版本：当 `enable` 的值为 `true` 时，该配置会直接覆盖 `rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger`。
+ 从 v8.5.5 起：当 `enable` 的值为 `true` 时，仅当 `storage.flow-control.l0-files-threshold` 小于 `rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger` 时才覆盖该 RocksDB 配置项，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。


Suggested change

+ v8.5.4 及之前版本：当 `enable` 的值为 `true` 时，该配置会直接覆盖 `rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger`。

+ 从 v8.5.5 起：当 `enable` 的值为 `true` 时，仅当 `storage.flow-control.l0-files-threshold` 小于 `rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger` 时才覆盖该 RocksDB 配置项，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

+ v8.5.4 及之前版本：当开启流控机制（[`enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置会直接覆盖 [`rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger`](/tikv-configuration-file.md#level0-slowdown-writes-trigger)。

+ 从 v8.5.5 和 v9.0.0 起：当开启流控机制（[`enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置仅在其值小于 [`rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger`](/tikv-configuration-file.md#level0-slowdown-writes-trigger) 时才覆盖 `rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger`，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

要考虑另一种描述方式吗，就是直接让用户参考下面那个配置项的描述也可以？这样避免一旦版本逻辑变更，需要改四处地方。

Suggested change

+ v8.5.4 及之前版本：当 `enable` 的值为 `true` 时，该配置会直接覆盖 `rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger`。

+ 从 v8.5.5 起：当 `enable` 的值为 `true` 时，仅当 `storage.flow-control.l0-files-threshold` 小于 `rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger` 时才覆盖该 RocksDB 配置项，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

> **注意**：

>

> 当满足一定条件时，`rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger` 的值会被该配置项覆盖。详细参考 [`rocksdb.(defaultcf|writecf|lockcf).level0-slowdown-writes-trigger`](/tikv-configuration-file.md#level0-slowdown-writes-trigger)。

qiancai · 2026-01-09T02:45:54Z

tikv-configuration-file.md

+ v8.5.4 及之前版本：当 `enable` 的值为 `true` 时，该配置会直接覆盖 `rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit`。
+ 从 v8.5.5 起：当 `enable` 的值为 `true` 时，仅当 `storage.flow-control.soft-pending-compaction-bytes-limit` 小于 `rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit` 时才覆盖该 RocksDB 配置项，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。


Suggested change

+ v8.5.4 及之前版本：当 `enable` 的值为 `true` 时，该配置会直接覆盖 `rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit`。

+ 从 v8.5.5 起：当 `enable` 的值为 `true` 时，仅当 `storage.flow-control.soft-pending-compaction-bytes-limit` 小于 `rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit` 时才覆盖该 RocksDB 配置项，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

+ v8.5.4 及之前版本：当开启流控机制（[`enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置会直接覆盖 [`rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit`](/tikv-configuration-file.md#soft-pending-compaction-bytes-limit-1)。

+ 从 v8.5.5 和 v9.0.0 起：当开启流控机制（[`enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置仅在其值小于 [`rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit`](/tikv-configuration-file.md#soft-pending-compaction-bytes-limit-1) 时才覆盖 `rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit`，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

另一种描述方式

Suggested change

+ v8.5.4 及之前版本：当 `enable` 的值为 `true` 时，该配置会直接覆盖 `rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit`。

+ 从 v8.5.5 起：当 `enable` 的值为 `true` 时，仅当 `storage.flow-control.soft-pending-compaction-bytes-limit` 小于 `rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit` 时才覆盖该 RocksDB 配置项，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

> **注意**：

>

> 当满足一定条件时，`rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit` 的值会被该配置项覆盖。详细参考 [`rocksdb.(defaultcf|writecf|lockcf).soft-pending-compaction-bytes-limit`](/tikv-configuration-file.md#soft-pending-compaction-bytes-limit-1。

qiancai · 2026-01-09T02:50:19Z

tikv-configuration-file.md

+ v8.5.4 及之前版本：当 `storage.flow-control.enable` 的值为 `true` 时，该配置项会被 `storage.flow-control.l0-files-threshold` 直接覆盖。
+ 从 v8.5.5 起：当 `storage.flow-control.enable` 的值为 `true` 时，如果本配置项的值大于 `storage.flow-control.l0-files-threshold`，则本配置项会被 `storage.flow-control.l0-files-threshold` 覆盖；否则保持本配置不变。


Suggested change

+ v8.5.4 及之前版本：当 `storage.flow-control.enable` 的值为 `true` 时，该配置项会被 `storage.flow-control.l0-files-threshold` 直接覆盖。

+ 从 v8.5.5 起：当 `storage.flow-control.enable` 的值为 `true` 时，如果本配置项的值大于 `storage.flow-control.l0-files-threshold`，则本配置项会被 `storage.flow-control.l0-files-threshold` 覆盖；否则保持本配置不变。

+ v8.5.4 及之前版本：当开启流控机制（[`storage.flow-control.enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置项会被 [`storage.flow-control.l0-files-threshold`](/tikv-configuration-file.md#l0-files-threshold) 直接覆盖。

+ 从 v8.5.5 和 v9.0.0 起：当开启流控机制（[`storage.flow-control.enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置项仅在其值大于 [`storage.flow-control.l0-files-threshold`](/tikv-configuration-file.md#l0-files-threshold 时会被 `storage.flow-control.l0-files-threshold` 覆盖，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

qiancai · 2026-01-09T02:50:35Z

tikv-configuration-file.md

+ v8.5.4 及之前版本：当 `storage.flow-control.enable` 的值为 `true` 时，该配置项会被 `storage.flow-control.soft-pending-compaction-bytes-limit` 直接覆盖。
+ 从 v8.5.5 起：当 `storage.flow-control.enable` 的值为 `true` 时，如果本配置项的值大于 `storage.flow-control.soft-pending-compaction-bytes-limit`，则本配置项会被 `storage.flow-control.soft-pending-compaction-bytes-limit` 覆盖；否则保持本配置不变。


Suggested change

+ v8.5.4 及之前版本：当 `storage.flow-control.enable` 的值为 `true` 时，该配置项会被 `storage.flow-control.soft-pending-compaction-bytes-limit` 直接覆盖。

+ 从 v8.5.5 起：当 `storage.flow-control.enable` 的值为 `true` 时，如果本配置项的值大于 `storage.flow-control.soft-pending-compaction-bytes-limit`，则本配置项会被 `storage.flow-control.soft-pending-compaction-bytes-limit` 覆盖；否则保持本配置不变。

+ v8.5.4 及之前版本：当开启流控机制（[`storage.flow-control.enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置项会被 [`storage.flow-control.soft-pending-compaction-bytes-limit`](/tikv-configuration-file.md#soft-pending-compaction-bytes-limit) 直接覆盖。

+ 从 v8.5.5 和 v9.0.0 起：当开启流控机制（[`storage.flow-control.enable`](/tikv-configuration-file.md#enable) 为 `true`）时，该配置项仅在其值大于 [`storage.flow-control.soft-pending-compaction-bytes-limit`](/tikv-configuration-file.md#soft-pending-compaction-bytes-limit) 时会被 `storage.flow-control.soft-pending-compaction-bytes-limit` 覆盖，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

Use reference-based approach to avoid duplication: - In flow-control config items, use brief note block to reference RocksDB config items - In RocksDB config items, keep detailed version-specific behavior with links This makes future version logic changes easier to maintain (only 2 places instead of 4). Signed-off-by: hhwyt <[email protected]>

ti-chi-bot · 2026-01-09T10:29:18Z

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hhwyt · 2026-01-09T10:39:58Z

/ok-to-test

hhwyt · 2026-01-09T10:40:19Z

@qiancai PTAL again, thx~

tikv-configuration-file.md

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		+ v8.5.4 及之前版本：当 `enable` 的值为 `true` 时，该配置会直接覆盖 `rocksdb.(defaultcf\|writecf\|lockcf).level0-slowdown-writes-trigger`。
		+ 从 v8.5.5 起：当 `enable` 的值为 `true` 时，仅当 `storage.flow-control.l0-files-threshold` 小于 `rocksdb.(defaultcf\|writecf\|lockcf).level0-slowdown-writes-trigger` 时才覆盖该 RocksDB 配置项，以避免在调大流控阈值时削弱 RocksDB 的 compaction 加速机制。

		+ v8.5.4 及之前版本：当 `storage.flow-control.enable` 的值为 `true` 时，该配置项会被 `storage.flow-control.l0-files-threshold` 直接覆盖。
		+ 从 v8.5.5 起：当 `storage.flow-control.enable` 的值为 `true` 时，如果本配置项的值大于 `storage.flow-control.l0-files-threshold`，则本配置项会被 `storage.flow-control.l0-files-threshold` 覆盖；否则保持本配置不变。

tikv-configuration-file: update flow-control override behavior for v8.5.5 #21244

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