cloud: document detailed Top SQL I/O dimensions

[jiong-nba]

What is changed, added or deleted? (Required)

• Document the detailed Top SQL I/O dimensions available in TiDB Cloud Clinic for TiDB Cloud Dedicated clusters hosted on AWS and running TiDB v8.5.9 or later.
• Explain that Logical Read, Logical Write, and Read IOPS replace the combined Logical IO sort dimension, while CPU and Network remain available.
• Clarify that Read IOPS is a foreground RocksDB block-read attribution signal rather than device-level IOPS.
• Update the Top SQL usage step to include the detailed I/O dimensions.

This PR targets release-8.5 because TiDB Cloud documentation is maintained on that branch for content reuse. The documented feature applies to eligible clusters running TiDB v8.5.9 or later.

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

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• master (the latest development version)
• v9.0 (TiDB 9.0 versions)
• v8.5 (TiDB 8.5 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)

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

• This PR is translated from: N/A
• Other reference link(s):
  • Tracking issue: Extend Top SQL resource dimensions with logical read/write and RocksDB block reads tikv/tikv#19867
  • TiKV: *: extend Top SQL resource dimensions tikv/tikv#19953
  • kvproto: resource_usage_agent: add RocksDB block read count to Top SQL resource dimensions kvproto#1498
  • TiDB Dashboard: topsql: support detailed TiKV IO dimensions tidb-dashboard#1917
  • Clinic UI: https://github.com/pingcap-inc/clinic-ui/pull/536
  • ng-monitoring: topsql: support detailed IO dimensions ng-monitoring#355
  • TiDB documentation: topsql: document detailed TiKV I/O dimensions #23532

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

Summary by CodeRabbit

• Documentation
  • Updated the TiDB Cloud Clinic Top SQL guidance for TiKV nodes.
  • Added information about the Logical Read, Logical Write, and Read IOPS metrics.
  • Clarified metric availability by cluster type, cloud platform, and TiDB version.
  • Clarified that Read IOPS represents an attribution signal, not physical storage-device IOPS.
  • Updated chart and table analysis instructions to reflect available aggregation dimensions.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The Top SQL documentation now describes updated TiKV metrics for supported TiDB Cloud Dedicated clusters. It also updates the chart and table analysis step to include the new aggregation dimensions.

Changes

Top SQL documentation

Layer / File(s)	Summary
Top SQL metrics and analysis guidance tidb-cloud/tidb-cloud-clinic.md	The documentation replaces Network Bytes and Logical IO Bytes with Logical Read, Logical Write, and Read IOPS for applicable TiKV nodes. It retains CPU and Network, clarifies Read IOPS attribution, and updates the available analysis dimensions.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Merge Risk: ⚪ Minimal · up to 97ce9

The documentation update clarifies detailed Top SQL I/O dimensions, but one minor wording issue currently conflates sorting metrics with aggregation dimensions and could briefly mislead readers; the risk is localized and does not indicate a broader merge blocker.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main documentation change: adding detailed Top SQL I/O dimensions for TiDB Cloud.
Description check	✅ Passed	The description covers the required change, affected TiDB version, related links, AI involvement, and applicable change classifications. The documented scope matches the pull request objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches

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Actionable comments posted: 1

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[coderabbitai]

🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Separate sort metrics from aggregation dimensions.

Line 114 describes CPU, network, and I/O metrics as aggregation dimensions. These metrics are Order By values. State the aggregation dimensions separately.

Replace the line with:

4. Analyze the charts and tables displayed by Top SQL. Depending on the selected node, cluster version, and available metrics, you can use Order By to inspect CPU, network, logical I/O, logical read, logical write, or Read IOPS hotspots. You can also use the available aggregation dimensions to analyze the results.

Sources: Coding guidelines, Path instructions