Add support for MADV_POPULATE_WRITE (Linux 5.14+) to force page population
AFTER munmap trimming in SuperSlab fallback path.
Changes:
1. core/box/ss_os_acquire_box.c (lines 171-201):
- Apply MADV_POPULATE_WRITE after munmap prefix/suffix trim
- Fallback to explicit page touch for kernels < 5.14
- Always cleanup suffix region (remove MADV_DONTNEED path)
2. core/superslab_cache.c (lines 111-121):
- Use MADV_POPULATE_WRITE instead of memset for efficiency
- Fallback to memset if madvise fails
Testing Results:
- Page faults: Unchanged (~145K per 1M ops)
- Throughput: -2% (4.18M → 4.10M ops/s with HAKMEM_SS_PREFAULT=1)
- Root cause: 97.6% of page faults are from libc memset in initialization,
not from SuperSlab memory access
Conclusion: MADV_POPULATE_WRITE is effective for SuperSlab memory,
but overall page fault bottleneck comes from TLS/shared pool initialization.
Startup warmup remains the most effective solution (already implemented
in bench_random_mixed.c with +9.5% improvement).
🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
Major refactoring to improve maintainability and debugging:
1. Split hakmem_tiny_superslab.c (1521 lines) into 7 focused files:
- superslab_allocate.c: SuperSlab allocation/deallocation
- superslab_backend.c: Backend allocation paths (legacy, shared)
- superslab_ace.c: ACE (Adaptive Cache Engine) logic
- superslab_slab.c: Slab initialization and bitmap management
- superslab_cache.c: LRU cache and prewarm cache management
- superslab_head.c: SuperSlabHead management and expansion
- superslab_stats.c: Statistics tracking and debugging
2. Created hakmem_tiny_superslab_internal.h for shared declarations
3. Added superslab_return_block() as single exit point for header writing:
- All backend allocations now go through this helper
- Prevents bugs where headers are forgotten in some paths
- Makes future debugging easier
4. Updated Makefile for new file structure
5. Added header writing to ss_legacy_backend_box.c and
ss_unified_backend_box.c (though not currently linked)
Note: Header corruption bug in Larson benchmark still exists.
Class 1-6 allocations go through TLS refill/carve paths, not backend.
Further investigation needed.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
