Review Checklist for CXL.cache Coherency Protocol focuses on Snoop response latency, cacheline conflict rate, and coherence transaction retry count. The purpose is to turn memory observations into mechanism-backed actions with explicit owners and release-safe validation.
Workload scope and SLA targets are explicit.
Environment tags are locked and reproducible.
First failing transition is proven by command-level evidence.
Owner and rollback criteria are documented.
Validation matrix covers performance, stability, and reliability.
Owners signed: coherency owner, CXL architect, RTL owner, validation owner.
CXL extends PCIe with coherency and memory semantics; each protocol layer has distinct enablement and debug needs.
CXL PROTOCOL LAYERS
CXL.io (enumerate) -> CXL.cache (coherency) -> CXL.mem (capacity)CXL ENABLEMENT RISK
mailbox timeout █████
cache conflict ████
HDM misconfig ███DVSEC inventory
mailbox command log
CXL.cache trace
CXL.mem region map
CXL.io enumerated but cache enable failed due to incomplete mailbox coherency mode negotiation.
Confirm CXL.io readiness before cache/mem enable
Trace coherency transactions under mixed CPU/device writers
Validate HDM metadata against OS memory registration
Ask: which latency, bandwidth, and reliability evidence proves this PCIe/CXL topic is closed under real traffic?
Always tie controller and PHY counter shifts to application latency and throughput outcomes.
Lock firmware timing profile, thermal condition, and DIMM state before comparing PCIe/CXL captures.
Chasing peak bandwidth while ignoring p99 latency and fairness tails.
Changing timing guardbands without separating SI noise from scheduling issues.
Declaring closure without reliability gates, fault injection, and regression replay.
A checklist here protects against false closure. Every item should map to a known memory failure mode.
For CXL.cache Coherency Protocol, minimum checklist: workload scope, Snoop response latency, cacheline conflict rate, and coherence transaction retry count, artifact evidence (Coherency transaction trace, state transition log, and conflict heatmap), bottleneck class, owner, rollback path, and corner-matrix validation.
If controller or firmware changed, include fairness and RAS checks. If PHY or package assumptions changed, include SI/PI and thermal guardband evidence.