diff --git a/tidb-performance-tuning-config.md b/tidb-performance-tuning-config.md index ed1c5fab3f63a..e77dcf450a5c9 100644 --- a/tidb-performance-tuning-config.md +++ b/tidb-performance-tuning-config.md @@ -125,7 +125,7 @@ soft-pending-compaction-bytes-limit = "192GiB" | [`concurrent-send-snap-limit`](/tikv-configuration-file.md#concurrent-send-snap-limit), [`concurrent-recv-snap-limit`](/tikv-configuration-file.md#concurrent-recv-snap-limit), and [`snap-io-max-bytes-per-sec`](/tikv-configuration-file.md#snap-io-max-bytes-per-sec) | Set limits for concurrent snapshot transfer and I/O bandwidth during TiKV scaling operations. Higher limits reduce scaling time by allowing faster data migration. | Adjusting these limits affects the trade-off between scaling speed and online transaction performance. | | [`in-memory-peer-size-limit`](/tikv-configuration-file.md#in-memory-peer-size-limit-new-in-v840) and [`in-memory-instance-size-limit`](/tikv-configuration-file.md#in-memory-instance-size-limit-new-in-v840) | Control the memory allocation for pessimistic lock caching at the Region and TiKV instance levels. Storing locks in memory reduces disk I/O and improves transaction performance. | Monitor memory usage carefully. Higher limits improve performance but increase memory consumption. | | [`rocksdb.max-manifest-file-size`](/tikv-configuration-file.md#max-manifest-file-size) | Set the maximum size of the RocksDB Manifest file, which logs the metadata about SST files and database state changes. Increasing this size reduces the frequency of Manifest file rewrites, thereby minimizing their impact on foreground write performance. | The default value is `128MiB`. In environments with a large number of SST files (for example, hundreds of thousands), frequent Manifest rewrites can degrade write performance. Adjusting this parameter to a higher value, such as `256MiB` or larger, can help maintain optimal performance. | -| [`rocksdb.titan`](/tikv-configuration-file.md#rocksdbtitan), [`rocksdb.defaultcf.titan`](/tikv-configuration-file.md#rocksdbdefaultcftitan), [`min-blob-size`](/tikv-configuration-file.md#min-blob-size), and [`blob-file-compression`](/tikv-configuration-file.md#blob-file-compression) | Enable the Titan storage engine to reduce write amplification and alleviate disk I/O bottlenecks. Particularly useful when RocksDB compaction cannot keep up with write workloads, resulting in accumulated pending compaction bytes. | Enable it when write amplification is the primary bottleneck. Trade-offs include: 1. Potential performance impact on primary key range scans. 2. Increased space amplification (up to 2x in the worst case). 3. Additional memory usage for blob cache. | +| [`rocksdb.titan`](/tikv-configuration-file.md#rocksdbtitan), [`rocksdb.defaultcf.titan`](/tikv-configuration-file.md#rocksdbdefaultcftitan), [`min-blob-size`](/tikv-configuration-file.md#min-blob-size), and [`blob-file-compression`](/tikv-configuration-file.md#blob-file-compression) | Enable the Titan storage engine to reduce write amplification and alleviate disk I/O bottlenecks. Particularly useful when RocksDB compaction cannot keep up with write workloads, resulting in accumulated pending compaction bytes. | Enable it when write amplification is the primary bottleneck. Trade-offs include: | | [`storage.scheduler-pending-write-threshold`](/tikv-configuration-file.md#scheduler-pending-write-threshold) | Set the maximum size of the write queue in the TiKV scheduler. When the total size of pending write tasks exceeds this threshold, TiKV returns a `Server Is Busy` error for new write requests. | The default value is `100MiB`. In scenarios with high write concurrency or temporary write spikes, increasing this threshold (for example, to `512MiB`) can help accommodate the load. However, if the write queue continues to accumulate and exceeds this threshold persistently, it might indicate underlying performance issues that require further investigation. | | [`storage.flow-control.l0-files-threshold`](/tikv-configuration-file.md#l0-files-threshold) | Control when write flow control is triggered based on the number of kvDB L0 files. Increasing the threshold reduces write stalls during high write workloads. | Higher thresholds might lead to more aggressive compactions when many L0 files exist. | | [`storage.flow-control.soft-pending-compaction-bytes-limit`](/tikv-configuration-file.md#soft-pending-compaction-bytes-limit) | Control the threshold for pending compaction bytes to manage write flow control. The soft limit triggers partial write rejections. | The default soft limit is `192GiB`. In write-intensive scenarios, if compaction processes cannot keep up, pending compaction bytes accumulate, potentially triggering flow control. Adjusting the limit can provide more buffer space, but persistent accumulation indicates underlying issues that require further investigation. | @@ -272,8 +272,8 @@ The following table compares throughput (operations per second) between the base | Item | Baseline (OPS) | Optimized (OPS) | Improvement | | ---------| ---- | ----| ----| -| load data | 2858.5 | 5074.3 | +77.59% | -| workloada | 2243.0 | 12804.3 | +470.86% | +| Load data | 2858.5 | 5074.3 | +77.59% | +| Workloada | 2243.0 | 12804.3 | +470.86% | #### Performance analysis @@ -461,7 +461,7 @@ You can control the execution mode of DML statements using the [`tidb_dml_type`] To use the bulk DML execution mode, set `tidb_dml_type` to `"bulk"`. This mode optimizes bulk data loading without conflicts and reduces memory usage during large write operations. Before using this mode, ensure that: -- Auto-commit is enabled. +- [`autocommit`](/system-variables.md#autocommit) is enabled. - The [`pessimistic-auto-commit`](/tidb-configuration-file.md#pessimistic-auto-commit-new-in-v600) configuration item is set to `false`. ```sql