hakmem/arena_INIT2_1t_256.strace

% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 87.50    0.000084           9         9           mmap
 12.50    0.000012          12         1           munmap
------ ----------- ----------- --------- --------- ----------------
100.00    0.000096           9        10           total
Tiny: fix header/stride mismatch and harden refill paths - Root cause: header-based class indexing (HEADER_CLASSIDX=1) wrote a 1-byte header during allocation, but linear carve/refill and initial slab capacity still used bare class block sizes. This mismatch could overrun slab usable space and corrupt freelists, causing reproducible SEGV at ~100k iters. Changes - Superslab: compute capacity with effective stride (block_size + header for classes 0..6; class7 remains headerless) in superslab_init_slab(). Add a debug-only bound check in superslab_alloc_from_slab() to fail fast if carve would exceed usable bytes. - Refill (non-P0 and P0): use header-aware stride for all linear carving and TLS window bump operations. Ensure alignment/validation in tiny_refill_opt.h also uses stride, not raw class size. - Drain: keep existing defense-in-depth for remote sentinel and sanitize nodes before splicing into freelist (already present). Notes - This unifies the memory layout across alloc/linear-carve/refill with a single stride definition and keeps class7 (1024B) headerless as designed. - Debug builds add fail-fast checks; release builds remain lean. Next - Re-run Tiny benches (256/1024B) in debug to confirm stability, then in release. If any remaining crash persists, bisect with HAKMEM_TINY_P0_BATCH_REFILL=0 to isolate P0 batch carve, and continue reducing branch-miss as planned. 2025-11-09 18:55:50 +09:00			`% time seconds usecs/call calls errors syscall`
			`------ ----------- ----------- --------- --------- ----------------`
			`87.50 0.000084 9 9 mmap`
			`12.50 0.000012 12 1 munmap`
			`------ ----------- ----------- --------- --------- ----------------`
			`100.00 0.000096 9 10 total`