docs(alluxio): add S3 high-concurrency read tuning guide

[CAICAIIs]

Ⅰ. Describe what this PR does

This PR adds bilingual documentation for a verified AlluxioRuntime + S3 high-concurrency read tuning guide.

It documents the investigation result from issue #5802:

• Fluid v1.0.8 + Alluxio 2.9.5 can reproduce the fio high-concurrency hang.
• Fluid master at the time of investigation + Alluxio 2.9.5 still reproduces the same behavior.
• The validation suggests the issue is mainly related to Alluxio 2.9.5 FUSE/client read-path pressure under high-concurrency S3 reads, rather than Fluid controller logic.

The new docs provide:

• the fio reproduction command
• observed failure symptoms
• recommended AlluxioRuntime properties and FUSE args
• Dataset and test Pod examples
• validation results from the reproduced environment
• risks and scope of the tuning configuration

This is intentionally a docs/example PR first. It does not change controller behavior or AlluxioRuntime defaults.

Ⅱ. Does this pull request fix one issue?

Addresses #5802

Ⅲ. List the added test cases (unit test/integration test) if any, please explain if no tests are needed.

No code tests are added because this is a documentation-only change.

The tuning configuration documented here was validated in the reproduced environment:

• fio numjobs=8/16/32/64 passed
• repeated numjobs=64 passed
• test Pods deleted normally
• Alluxio master/worker/fuse stayed Running with restart count 0
• no DeadlineExceededRuntimeException, Timer expired, or OutOfDirectMemoryError

Ⅳ. Describe how to verify it

Review the rendered docs:

• docs/en/samples/alluxio_s3_high_concurrency.md
• docs/zh/samples/alluxio_s3_high_concurrency.md

Local checks run:

• git diff --check upstream/master...HEAD
• check_dco.sh upstream/master
• check_pr.sh --base upstream/master

Ⅴ. Special notes for reviews

This PR documents a tuning/configuration guide, not an upstream Alluxio internal fix.

The documented settings are intended for S3-compatible high-concurrency read workloads similar to #5802. Different S3 backends, object sizes, network latency, or concurrency levels may still require tuning.

If maintainers prefer productizing this in Fluid after reviewing the docs, I can follow up with a separate opt-in implementation PR.

[fluid-e2e-bot]

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[fluid-e2e-bot]

Hi @CAICAIIs. Thanks for your PR.

I'm waiting for a fluid-cloudnative 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[gemini-code-assist]

Code Review

This pull request introduces a new tuning guide in both English and Chinese for optimizing AlluxioRuntime performance during high-concurrency read operations from S3-compatible backends. The documentation provides a validated configuration profile, including JVM options and FUSE arguments, to address potential hangs and stability issues. Feedback from the review suggests improving the examples by using generic placeholders for local paths and specifying a container image that includes the 'fio' utility to ensure the test scenarios are reproducible.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.13%. Comparing base (9291dee) to head (7828644).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

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  Coverage   59.13%   59.13%           
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  Files         480      480           
  Lines       32611    32611           
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  Hits        19284    19284           
  Misses      11759    11759           
  Partials     1568     1568           

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cheyang]

/ok-to-test

[cheyang]

/lgtm /approve

This is a comment-only PR (documentation addition). All required checks pass, DCO verified.