pitr: add more description for performance parameters #21503
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Summary of Changes
Hello @3pointer, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
I've updated the Point-in-Time Recovery (PITR) guide to provide more comprehensive descriptions for performance-related parameters. This change specifically focuses on explaining pitr-batch-size and pitr-batch-count, which are crucial for optimizing restore performance, particularly in scenarios where many small files are generated due to numerous regions and short flush intervals. The added details will help users understand how to effectively tune these parameters to improve throughput and reduce overhead during PITR operations.
Highlights
- PITR Performance Documentation: Added detailed descriptions for
pitr-batch-sizeandpitr-batch-countparameters in thebr/br-pitr-guide.mdfile. These parameters help optimize restore performance by controlling batching of small files during PITR. - Batching Logic Clarification: Clarified that
pitr-batch-size(cumulative bytes per batch) andpitr-batch-count(number of files per batch) are equivalent in effect and evaluated independently, with the first one reached closing the batch.
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| > When the upstream has **many Regions** and a **short flush interval**, PITR produces lots of small files. This can increase batching/dispatch overhead during restore. You can **moderately** increase the following to raise the number of files processed per batch and improve throughput: | ||
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| - `pitr-batch-size`: cumulative **bytes per batch** (default **16 MiB**). | ||
| - `pitr-batch-count`: **number of files per batch** (default **8**). | ||
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| > The two thresholds are **equivalent in effect** and **evaluated independently**: **whichever is reached first** closes the current batch and starts the next; once one is met, the **other is ignored** for that batch. |
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Thanks for adding these details. For better clarity and to align with the style guide, I have a few suggestions for the wording:12
- In the first sentence, "lots of" is a bit informal. "a large number of" would be better.
- The last sentence is a bit complex and uses passive voice. It can be simplified for easier reading.
Style Guide References
| > When the upstream has **many Regions** and a **short flush interval**, PITR produces lots of small files. This can increase batching/dispatch overhead during restore. You can **moderately** increase the following to raise the number of files processed per batch and improve throughput: | |
| - `pitr-batch-size`: cumulative **bytes per batch** (default **16 MiB**). | |
| - `pitr-batch-count`: **number of files per batch** (default **8**). | |
| > The two thresholds are **equivalent in effect** and **evaluated independently**: **whichever is reached first** closes the current batch and starts the next; once one is met, the **other is ignored** for that batch. | |
| > When the upstream has **many Regions** and a **short flush interval**, PITR produces a large number of small files. This can increase batching/dispatch overhead during restore. You can **moderately** increase the following to raise the number of files processed per batch and improve throughput: | |
| - `pitr-batch-size`: cumulative **bytes per batch** (default **16 MiB**). | |
| - `pitr-batch-count`: **number of files per batch** (default **8**). | |
| > These two thresholds are evaluated independently. Whichever threshold is met first closes the current batch and starts the next. The other threshold is then ignored for that batch. |
Footnotes
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