Linux DAMON & Proactive Memory Reclamation Studio

Architect autonomous memory optimization with Linux DAMON (Data Access MONitor) and DAMOS schemes. Simulate adaptive region splitting and merging, evaluate cold-memory proactive pageout, and design multi-tiered CXL and NUMA memory migration policies with bounded 1% CPU overhead.

The Adaptive Region Split & Merge Algorithm

DAMON guarantees negligible CPU consumption through dynamic spatial aggregation:

• Initial Segmentation: The target virtual memory space is initially partitioned into $N$ coarse regions (e.g. 10 to 1,000 regions).
• Randomized Sampling: During each sampling interval, DAMON checks access bits on a single randomly selected page within each region, amortizing TLB and PTE walking overhead.
• Aggregation & Region Merging: At each aggregation interval, DAMON tallies access counts. Contiguous regions with identical access frequencies are automatically coalesced into larger super-regions.
• Selective Splitting: Regions exhibiting divergent internal access counts are split into smaller pieces, dynamically focusing resolution on hot boundary zones.

CXL Multi-Tier Memory Optimization

Modern hyperscale servers feature heterogeneous memory tiers (Fast Local DDR5 vs Expanded CXL 2.0 Bus Memory):

• Hierarchical Demotion: DAMOS continuously moves pages that haven’t been accessed for $> 10$ seconds from Node 0 (Local DRAM) to Node 2 (CXL expander) using action: migrate_cold.
• Zero Latency Jitter: Applications continue executing without realizing pages have shifted across physical interconnects.
• Hugepage Preservation: DAMON coordinates with transparent hugepages (THP), splitting and collapsing 2MB hugepages only when access patterns demand fine-grained migration.