in_process_exporter_metrics: Fix the reported RSS ram

[anagno]

The RSS value exported through process_memory_bytes was taken directly from /proc/pid/stat, which is reported in pages rather than bytes.

So before exposing the metric we have to convert to bytes, by using the size of pages

I tested it with my devices and now the results match the ones from htop

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Testing
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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes
  • Corrected process memory RSS metrics so values are accurately converted from system memory pages to bytes.
  • Added safeguards for environments where the system page size cannot be determined, improving metric reliability.
  • Virtual memory metrics remain unchanged.

[coderabbitai]

📝 Walkthrough

Walkthrough

The process exporter now caches the system page size during configuration and uses it to convert procfs RSS page counts to bytes when collecting memory metrics.

Changes

Process exporter memory metrics

Layer / File(s)	Summary
Page-size initialization plugins/in_process_exporter_metrics/pe.h, plugins/in_process_exporter_metrics/pe_config.c	Adds page_size to flb_pe and initializes it with sysconf(_SC_PAGESIZE).
RSS pages-to-bytes conversion plugins/in_process_exporter_metrics/pe_process.c	Multiplies RSS pages by the cached page size when the page size is positive; virtual memory handling remains unchanged.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: cosmo0920

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: correcting RSS memory reporting in in_process_exporter_metrics.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@plugins/in_process_exporter_metrics/pe_config.c`:
- Around line 43-45: Update the page-size initialization in the pe_config setup
to detect when sysconf(_SC_PAGESIZE) returns a non-positive value, then emit a
warning or apply an explicit fallback before RSS conversion proceeds. Preserve
the existing page_size value and downstream RSS-skipping behavior when the
lookup fails.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 6b5a0f53-cfe2-4dba-8d7f-3b66d43f0c21

📥 Commits

Reviewing files that changed from the base of the PR and between c830fb6 and ee657f2.

📒 Files selected for processing (3)

• plugins/in_process_exporter_metrics/pe.h
• plugins/in_process_exporter_metrics/pe_config.c
• plugins/in_process_exporter_metrics/pe_process.c

[cosmo0920]

Good catch! Thanks for the fix.

[anagno]

@cosmo0920 Am I the reason for the failing test or is it flaky?

[cosmo0920]

@cosmo0920 Am I the reason for the failing test or is it flaky?

The failing test is one of the flaky tests. So, it's okey to merge.