Supporting write-through caching with high-performance TSO for resilient CXL systems

Ocalan, Burak

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https://hdl.handle.net/2142/129929 Copy

Description

Title

Supporting write-through caching with high-performance TSO for resilient CXL systems

Author(s)

Ocalan, Burak

Issue Date

2025-07-11

Director of Research (if dissertation) or Advisor (if thesis)

Torrellas, Josep

Department of Study

Siebel School Comp & Data Sci

Discipline

Computer Science

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• write-through
• TSO
• CXL

Abstract

Current multiprocessors that support the total store order (TSO) memory consistency model invariably use write-back (WB) caches. When their hardware needs to issue write-through (WT) stores as in uncached operations, they deliver dismal performance: writes to memory have to be fully serialized, often forcing the program to observe the full latency of a round-trip to memory. To solve this problem, this thesis presents a novel architecture that supports high-performance TSO for WT caching environments. The architecture, called PhasedStore, involves extending the store queue of the core with additional states. Individual WT stores operate in two phases, which allow them to fully overlap with other stores and still satisfy TSO. PhasedStore is useful in environments that require a WT cache coherence protocol. This is the case in a setting that this thesis explores: a cache-coherent CXL distributed shared memory system in the presence of compute node failures. In this environment, to simplify recovery, we support a WT directory-based protocol which guarantees that stores are propagated to the CXL memory before updating the caches. Our evaluation shows that PhasedStore is very effective. Compared to a conventional approach to enforce TSO in a WT protocol, PhasedStore reduces the average execution time of a set of parallel applications by 2.21x. Further, the applications' execution time is only 1.40x higher than with a TSO WB protocol that includes no resilience consideration.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129929

Copyright and License Information

Copyright 2025 Burak Ocalan

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