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tikv: recorrect the descriptions on the feature region-split-size part. #15611

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tikv: recorrect the descriptions on the feature region-split-size part. #15611

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16 changes: 8 additions & 8 deletions tune-region-performance.md
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Expand Up @@ -11,21 +11,21 @@ This document introduces how to tune Region performance by adjusting the Region

TiKV automatically [shards bottom-layered data](/best-practices/tidb-best-practices.md#data-sharding). Data is split into multiple Regions based on the key ranges. When the size of a Region exceeds a threshold, TiKV splits it into two or more Regions.

When processing a large amount of data, TiKV might split too many Regions, which causes more resource consumption and [performance regression](/best-practices/massive-regions-best-practices.md#performance-problem). For a certain amount of data, the larger the Region size, the fewer the Regions. Since v6.1.0, TiDB supports setting customizing Region size. The default size of a Region is 96 MiB. To reduce the number of Regions, you can adjust Regions to a larger size.
In scenarios involving large datasets, if the Region size is relatively small, TiKV might have numerous Regions, which causes more resource consumption and [performance regression](/best-practices/massive-regions-best-practices.md#performance-problem). Since v6.1.0, TiDB supports customizing Region size. The default size of a Region is 96 MiB. To reduce the number of Regions, you can adjust Regions to a larger size.
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To reduce the performance overhead of many Regions, you can also enable [Hibernate Region](/best-practices/massive-regions-best-practices.md#method-4-increase-the-number-of-tikv-instances) or [`Region Merge`](/best-practices/massive-regions-best-practices.md#method-5-adjust-raft-base-tick-interval).

## Use `region-split-size` to adjust Region size

> **Warning:**
> **Note:**
>
> Currently, customized Region size is an experimental feature introduced in TiDB v6.1.0. It is not recommended that you use it in production environments. The risks are as follows:
> The recommended range for the Region size is [48MiB, 258MiB]. Commonly used sizes include 96 MiB, 128 MiB, and 256 MiB. It is NOT recommended to set the Region size beyond 1 GiB. Avoid setting the size to more than 10 GiB. An excessively large Region size might result in the following side impacts:
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>
> + Performance jitter might be caused.
> + The query performance, especially for queries that deal with a large range of data, might decrease.
> + The Region scheduling slows down.
> + Performance jitters
> + Decreased query performance, especially for queries that deal with a large range of data
> + Slower Region scheduling

To adjust the Region size, you can use the [`coprocessor.region-split-size`](/tikv-configuration-file.md#region-split-size) configuration item. The recommended sizes are 96 MiB, 128 MiB, or 256 MiB. The larger the `region-split-size` value, the more jittery the performance will be. It is NOT recommended to set the Region size over 1 GiB. Avoid setting the size to more than 10 GiB. When TiFlash is used, the Region size should not exceed 256 MiB.
To adjust the Region size, you can use the [`coprocessor.region-split-size`](/tikv-configuration-file.md#region-split-size) configuration item. When TiFlash is used, the Region size should not exceed 256 MiB.

When the Dumpling tool is used, the Region size should not exceed 1 GiB. In this case, you need to reduce the concurrency after increasing the Region size; otherwise, TiDB might run out of memory.

Expand All @@ -35,4 +35,4 @@ When the Dumpling tool is used, the Region size should not exceed 1 GiB. In this
>
> Currently, this is an experimental feature introduced in TiDB v6.1.0. It is not recommended that you use it in production environments.

When Regions are set to a larger size, you need to set [`coprocessor.enable-region-bucket`](/tikv-configuration-file.md#enable-region-bucket-new-in-v610) to `true` to increase the query concurrency. When you use this configuration, Regions are divided into buckets. Buckets are smaller ranges within a Region and are used as the unit of concurrent query to improve the scan concurrency. You can control the bucket size using [`coprocessor.region-bucket-size`](/tikv-configuration-file.md#region-bucket-size-new-in-v610).
After Regions are set to a larger size, if you want to further improve the query concurrency, you can set [`coprocessor.enable-region-bucket`](/tikv-configuration-file.md#enable-region-bucket-new-in-v610) to `true`. When you use this configuration, Regions are divided into buckets. Buckets are smaller ranges within a Region and are used as the unit of concurrent query to improve the scan concurrency. You can control the bucket size using [`coprocessor.region-bucket-size`](/tikv-configuration-file.md#region-bucket-size-new-in-v610).
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