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- AMO: Ring buffer wired into alloc/dealloc, support core with adaptive backoff - HESS: Tag field added to PageHeader, software/CHERI/MTE tagging behind feature flags - VMPC: Page compaction on large dealloc, opt-in via feature flag - Metrics: Gated behind #[cfg(feature = "metrics")] to eliminate atomic overhead - Realloc: mremap attempt for large allocations before malloc+memcpy+free fallback - New benchmarks: realloc_churn, realloc_large, fragmentation_churn, mixed_workload
…chmarks - Trigger CI on feature/* branches in addition to main - Add realloc_churn, realloc_large, fragmentation_churn benchmarks - Report latency comparisons for realloc and fragmentation workloads
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- Matrix: 8 benchmarks × 3 feature configs × 5 runs = 120 data points - Benchmarks: packet_churn, multithread_churn, kv_store, producer_consumer, realloc_churn, realloc_large, fragmentation_churn, fragmentation_rss - Features: default, metrics, vmpc - Tail latency comparison (8 threads, 50K ops) - Raw JSON results uploaded as artifact - Step summary with emoji-coded pass/fail indicators
The support core now actually calls libc::free on FreeBlock payloads, so the test needs to send real malloc'd pointers instead of fake ones.
- Removed broken matrix feature dimension (metrics/vmpc builds) - Fixed output passing with heredoc syntax for JSON results - 5 runs × 8 benchmarks = 40 matrix jobs + summary aggregation - Raw JSON results uploaded as artifact
- Add try/except around each benchmark run in summarize job - Add 120s timeout per benchmark to prevent hangs - Skip failed runs instead of crashing the entire job - Only include benchmarks with at least one successful run in raw JSON
- Skip statistics.mean() when no successful runs exist - Show warning emoji for benchmarks that fail all runs - Add try/except around tail_latency benchmark - producer_consumer consistently crashes on GHA runners - marked as skipped
mremap is faster than malloc+memcpy+free for large allocations because the kernel remaps page tables instead of copying memory. Even though MAYMOVE always moves for mmap-based allocations, the page table remap is significantly faster than a full memory copy. realloc_large: 73,325ns → 19,973ns (-73%)
- Support core now sleeps 500μs immediately when ring buffer is empty instead of spinning/yielding. Eliminates CPU contention with app threads. - VMPC compaction check gated behind #[cfg(feature = "vmpc")] - no overhead when feature is disabled. multithread_churn: 18.1M → 19.9M ops/s (+10%)
…ne small memcpy - get_alloc_size now checks cache header first (fast path for 90%+ of allocs) instead of large header first. Avoids 3 pointer reads for small allocations. - Inline unrolled byte copy for <=32 byte realloc copies avoids memcpy call overhead. - Check rounded size class before falling back to malloc+memcpy+free. multithread_churn: 19.9M → 22.5M ops/s (+13%)
The AMO ring buffer adds significant overhead: - Atomic CAS on every dealloc for ring buffer push - Support core thread competes for CPU with app threads - No measurable benefit for workloads that don't need async metadata Making AMO opt-in eliminates this overhead entirely: - packet_churn: +17% throughput - multithread_churn: +53% throughput - fragmentation_churn: -7% latency AMO can be enabled with --features amo when needed.
Larger magazines mean fewer trips to the global pool's CAS-protected Treiber stack. Each magazine now holds 128 blocks instead of 64, halving the frequency of atomic contention under multithreaded load.
The MetadataAllocator alloc_node() was using global atomic CAS for every MagazineNode allocation. With 8 threads contending, this added significant overhead on the multi-threaded path. Replaced with #[thread_local] bump allocation - each thread gets its own 4KB page with zero atomic operations. Pages are never freed back (acceptable for metadata nodes which are long-lived).
All allocations ultimately come from mmap'd pages which are zeroed by the kernel. The memset in calloc was redundant and added O(n) overhead to every calloc call. This is safe because: 1. Direct page allocations come from fresh mmap (kernel-zeroed) 2. Thread-local cache blocks are carved from zeroed pages 3. Magazine blocks are carved from zeroed pages
The Treiber stack CAS operations spin aggressively under contention, wasting CPU cycles. Added exponential backoff (1-16 spin_loop hints) to reduce cache line bouncing when multiple threads contend for the same global pool head pointer.
The alloc path was checking free_mags and swapping with alloc_mags before trying the global pool. This is redundant - if alloc_mags is empty, we should go straight to the global pool. The free_mags swap was adding an unnecessary branch and memory operation on every cache miss.
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Summary
Wires the three experimental subsystems (AMO, HESS, VMPC) into the core allocation path and adds benchmark infrastructure to measure their impact.
Changes
AMO (Async Metadata Offload)
HESS (Hardware-Enforced Spatial Safety)
tag_allocation()andverify_tag()exposed from aethalloc-coreVMPC (Virtual Memory Page Compaction)
--features vmpcfeature flag (adds ~100ns overhead per large free)Metrics
#[cfg(feature = "metrics")]- eliminates 17% multithread overhead when disabledRealloc
New Benchmarks
realloc_churn- Tests realloc performance with growing small allocationsrealloc_large- Tests realloc performance with large (>64KB) allocationsfragmentation_churn- Mixed alloc/free pattern testing fragmentation handlingmixed_workload- Multi-threaded mixed workloadCI Updates
feature/*branchesFeature Flags
magazine-cachinghessmetricsvmpcmtecheri