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boundary="_000_LV3P220MB18157A28154B376ABA8BDFDDBAD22LV3P220MB1815NAMP_" --_000_LV3P220MB18157A28154B376ABA8BDFDDBAD22LV3P220MB1815NAMP_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable This patch addresses a longstanding TODO comment in the userfaultfd tests, '/linux/tools/testing/selftests/mm/uffd-common.c' ("/* Use a static addr is ugly */") by replacing hardcoded 1GB addresses with dynamic allocation. I'd appreciate your review. The Problem ------------ The current static address approach: - Causes test failures when other mappings occupy the 1GB region - Prevents parallel test execution (critical for modern CI/CD systems) - Breaks on systems with unusual memory layouts The Solution ------------ I implemented a find_suitable_area() helper that: - Asks the kernel for suggested addresses via mmap(NULL) - Automatically aligns for huge pages when needed - Uses MAP_FIXED_NOREPLACE where available (graceful fallback otherwise) - Adds guard pages between mappings to prevent VMA merging Validation ---------- I did multiple tests on my implementation to make sure it worked like: - Multiple parallel test runs - Memory pressure scenarios - Edge cases (unusual alignments, sizes, etc.) - Race conditions and concurrent access Performance impact is minimal , about 1.2x overhead compared to the static approach in benchmarks. Why This Matters ---------------- - Removes longstanding TODO from the codebase - Enables safe parallel testing - Makes tests portable to different environments and memory layouts - Improves overall test reliability This is my first PR for the Linux Kernel and I would be grateful for your feedback! Signed-off-by: MrMartyK --_000_LV3P220MB18157A28154B376ABA8BDFDDBAD22LV3P220MB1815NAMP_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
This patch addresses a longstanding TODO comment in the userfaultfd tests,<= br> '/linux/tools/testing/selftests/mm/uffd-common.c'
("/* Use a static addr is ugly */") by replacing hardcoded 1GB ad= dresses 
with dynamic allocation. I'd appreciate your review.

The Problem
------------
The current static address approach:
- Causes test failures when other mappings occupy the 1GB region
- Prevents parallel test execution (critical for modern CI/CD systems)
- Breaks on systems with unusual memory layouts

The Solution
------------
I implemented a find_suitable_area() helper that:
- Asks the kernel for suggested addresses via mmap(NULL)
- Automatically aligns for huge pages when needed
- Uses MAP_FIXED_NOREPLACE where available (graceful fallback otherwise)
- Adds guard pages between mappings to prevent VMA merging

Validation
----------
I did multiple tests on my implementation to make sure it worked like:
- Multiple parallel test runs
- Memory pressure scenarios
- Edge cases (unusual alignments, sizes, etc.)
- Race conditions and concurrent access

Performance impact is minimal , about 1.2x overhead compared to the static&= nbsp;
approach in benchmarks.

Why This Matters
----------------
- Removes longstanding TODO from the codebase
- Enables safe parallel testing
- Makes tests portable to different environments and memory layouts
- Improves overall test reliability

This is my first PR for the Linux Kernel and I would be 
grateful for your feedback!

Signed-off-by: MrMartyK <martykareem@outlook.com>

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