OpenXiangShan/GEM5
Oct 2024 – Feb 2026
15 Months active
Languages Used
C++BashPythonShellScalaYAMLMarkdown
Technical Skills
Embedded SystemsLow-Level ProgrammingRISC-V ArchitectureBug FixingCI/CDCPU Architecture
ZHEN HAO
PROFILE
Zhen Hao
Over 15 months, contributed to the OpenXiangShan/GEM5 repository by developing and refining advanced memory subsystem features, simulation tools, and debugging instrumentation. Delivered enhancements such as SV48 page table support, Ramulator memory simulator integration, and adaptive prefetching mechanisms, focusing on configurability and performance analysis. Addressed complex bugs in RISC-V interrupt handling, TLB validation, and CSR access, improving simulation fidelity and system reliability. Leveraged C++, Python, and Bash to implement automated calibration frameworks, profiling counters, and dynamic configuration options. Emphasized maintainable code, robust documentation, and data-driven optimization, enabling more accurate architectural modeling and streamlined workflows for research and development teams.
Overall Statistics
Feature vs Bugs
73%Features
Repository Contributions
26Total
Bugs
7
Commits
26
Features
19
Lines of code
2,310
Activity Months15
Your Network
35 peopleShared Repositories
27
Work History
February 2026
1 Commits • 1 Features
Feb 1, 2026February 2026 – OpenXiangShan/GEM5: Delivered MemRenaming analysis to improve memory access tracking and profiling. Implemented tracking of load instructions with reused addresses and store-load producer-consumer relationships, and added profiling checks for forward memory accesses to enhance performance visibility. This work strengthens memory performance modeling and provides actionable data for optimization and debugging.
1 Commits • 1 Features
Feb 1, 2026February 2026 – OpenXiangShan/GEM5: Delivered MemRenaming analysis to improve memory access tracking and profiling. Implemented tracking of load instructions with reused addresses and store-load producer-consumer relationships, and added profiling checks for forward memory accesses to enhance performance visibility. This work strengthens memory performance modeling and provides actionable data for optimization and debugging.
February 2026
January 2026
2 Commits • 2 Features
Jan 1, 2026January 2026 monthly summary for OpenXiangShan/GEM5: Focused on improving profiling observability and developer guidance. Key features delivered include a new performance counter for memory renaming loads to enhance profiling (MEMRenaming) and documentation improvements clarifying KMH-V2-CONFIG branch usage. No major bugs fixed this month; emphasis was on reliability, maintainability, and onboarding. Overall impact: stronger profiling capabilities, better developer guidance, and a smoother path for future performance work. Technologies/skills demonstrated: performance profiling, memory renaming, repository maintenance, and documentation best practices. Business value: faster identification of performance bottlenecks and reduced risk of misconfiguration, enabling quicker iterations and improved performance outcomes.
January 2026
2 Commits • 2 Features
Jan 1, 2026January 2026 monthly summary for OpenXiangShan/GEM5: Focused on improving profiling observability and developer guidance. Key features delivered include a new performance counter for memory renaming loads to enhance profiling (MEMRenaming) and documentation improvements clarifying KMH-V2-CONFIG branch usage. No major bugs fixed this month; emphasis was on reliability, maintainability, and onboarding. Overall impact: stronger profiling capabilities, better developer guidance, and a smoother path for future performance work. Technologies/skills demonstrated: performance profiling, memory renaming, repository maintenance, and documentation best practices. Business value: faster identification of performance bottlenecks and reduced risk of misconfiguration, enabling quicker iterations and improved performance outcomes.
December 2025
1 Commits • 1 Features
Dec 1, 2025Month: 2025-12 Key features delivered: - Adaptive BOP offset optimization in GEM5 for OpenXiangShan: Calibrates BOP hash and enables adaptive offset to optimize prefetching based on runtime conditions, improving memory access efficiency in GEM5. Major bugs fixed: - No major bugs fixed this period. The focus was on feature delivery and configuration enhancements for memory subsystem optimization. Overall impact and accomplishments: - Introduced adaptive BOP offset capability in GEM5, providing a more responsive memory subsystem tuning path for simulations and workloads. - This work establishes a foundation for further memory system optimizations and measurable performance improvements in GEM5-based simulations. - All changes are traceable via commit 28a10b3b1a9b9f64be102367fa2c66aee36a05be, including mem: Calibrate bop config and mem: Update bop Config, with Change-Id I898480eeac3589f24233760d8cbe80076a674d16 and I9a6ec7883ed95d093b7e2bb481269628c08b407e. Technologies/skills demonstrated: - Memory subsystem tuning and calibration (bop config, hash calibration, adaptOffset). - Feature flag utilization and configuration management in GEM5. - Version control traceability and Change-Id-based commits.
1 Commits • 1 Features
Dec 1, 2025Month: 2025-12 Key features delivered: - Adaptive BOP offset optimization in GEM5 for OpenXiangShan: Calibrates BOP hash and enables adaptive offset to optimize prefetching based on runtime conditions, improving memory access efficiency in GEM5. Major bugs fixed: - No major bugs fixed this period. The focus was on feature delivery and configuration enhancements for memory subsystem optimization. Overall impact and accomplishments: - Introduced adaptive BOP offset capability in GEM5, providing a more responsive memory subsystem tuning path for simulations and workloads. - This work establishes a foundation for further memory system optimizations and measurable performance improvements in GEM5-based simulations. - All changes are traceable via commit 28a10b3b1a9b9f64be102367fa2c66aee36a05be, including mem: Calibrate bop config and mem: Update bop Config, with Change-Id I898480eeac3589f24233760d8cbe80076a674d16 and I9a6ec7883ed95d093b7e2bb481269628c08b407e. Technologies/skills demonstrated: - Memory subsystem tuning and calibration (bop config, hash calibration, adaptOffset). - Feature flag utilization and configuration management in GEM5. - Version control traceability and Change-Id-based commits.
December 2025
November 2025
2 Commits • 2 Features
Nov 1, 2025Month: 2025-11 — OpenXiangShan/GEM5 delivered two major features enhancing observability and configurability of the memory subsystem. Virtual Address Tracing adds logging of virtual address accesses in the architecture database to support debugging, memory management, and performance analysis. XS-Stride Configuration Tuning calibrates stride entries with a tree-based replacement policy and relaxes non-power-of-two errors to warnings, increasing configuration flexibility and stability. No major bugs fixed this month; focus was on feature delivery and architecture robustness. Impact includes faster root-cause analysis, broader hardware-model support, and easier deployment in production environments. Technologies/skills demonstrated: memory hierarchy design, archdb integration, tree-based data structures, configuration policy design, and change management.
November 2025
2 Commits • 2 Features
Nov 1, 2025Month: 2025-11 — OpenXiangShan/GEM5 delivered two major features enhancing observability and configurability of the memory subsystem. Virtual Address Tracing adds logging of virtual address accesses in the architecture database to support debugging, memory management, and performance analysis. XS-Stride Configuration Tuning calibrates stride entries with a tree-based replacement policy and relaxes non-power-of-two errors to warnings, increasing configuration flexibility and stability. No major bugs fixed this month; focus was on feature delivery and architecture robustness. Impact includes faster root-cause analysis, broader hardware-model support, and easier deployment in production environments. Technologies/skills demonstrated: memory hierarchy design, archdb integration, tree-based data structures, configuration policy design, and change management.
October 2025
1 Commits • 1 Features
Oct 1, 2025October 2025: Focused on expanding simulation fidelity by integrating Ramulator memory simulation capabilities into the XS-GEM5 framework, enabling detailed end-to-end memory subsystem analysis for GEM5-based research and development.
1 Commits • 1 Features
Oct 1, 2025October 2025: Focused on expanding simulation fidelity by integrating Ramulator memory simulation capabilities into the XS-GEM5 framework, enabling detailed end-to-end memory subsystem analysis for GEM5-based research and development.
October 2025
September 2025
3 Commits • 3 Features
Sep 1, 2025OpenXiangShan/GEM5 — 2025-09 monthly summary. Focused on delivering configurable automation enhancements, memory subsystem optimizations, and safer cross-component integration between gem5 and NEMU. The work improved calibration automation, prefetch accuracy, and CSR synchronization control, enabling faster iteration, higher fidelity simulations, and reduced integration risk.
September 2025
3 Commits • 3 Features
Sep 1, 2025OpenXiangShan/GEM5 — 2025-09 monthly summary. Focused on delivering configurable automation enhancements, memory subsystem optimizations, and safer cross-component integration between gem5 and NEMU. The work improved calibration automation, prefetch accuracy, and CSR synchronization control, enabling faster iteration, higher fidelity simulations, and reduced integration risk.
August 2025
2 Commits • 2 Features
Aug 1, 2025Monthly summary for 2025-08 focusing on delivering automation, configurability, and performance-related enhancements for the GEM5-based OpenXiangShan project. The primary work this month concentrated on building automation around parameter calibration, along with a dynamic feature flag for the PHT prefetcher to improve runtime configurability and experimental throughput.
2 Commits • 2 Features
Aug 1, 2025Monthly summary for 2025-08 focusing on delivering automation, configurability, and performance-related enhancements for the GEM5-based OpenXiangShan project. The primary work this month concentrated on building automation around parameter calibration, along with a dynamic feature flag for the PHT prefetcher to improve runtime configurability and experimental throughput.
August 2025
July 2025
1 Commits • 1 Features
Jul 1, 2025July 2025 monthly summary for OpenXiangShan/GEM5 focusing on a practical, business-value oriented update.
July 2025
1 Commits • 1 Features
Jul 1, 2025July 2025 monthly summary for OpenXiangShan/GEM5 focusing on a practical, business-value oriented update.
June 2025
1 Commits
Jun 1, 2025June 2025 monthly performance summary for OpenXiangShan/GEM5 development focusing on memory subsystem reliability and RISC-V path correctness.
1 Commits
Jun 1, 2025June 2025 monthly performance summary for OpenXiangShan/GEM5 development focusing on memory subsystem reliability and RISC-V path correctness.
June 2025
May 2025
1 Commits
May 1, 2025May 2025 monthly summary for OpenXiangShan/GEM5. Delivered a critical RISC-V CSR access bug fix improving correctness of cycle/time register handling across S- and U-modes. The fix updates mcounteren to enable S-/U-mode access and adjusts NEMU_COUNTER_MASK to ensure writes take effect, preventing timing/counting gaps in privileged-mode operation. Performed targeted validation and code review, aligning with architectural CSR handling and enabling more reliable OS timing, performance measurements, and test reproducibility.
May 2025
1 Commits
May 1, 2025May 2025 monthly summary for OpenXiangShan/GEM5. Delivered a critical RISC-V CSR access bug fix improving correctness of cycle/time register handling across S- and U-modes. The fix updates mcounteren to enable S-/U-mode access and adjusts NEMU_COUNTER_MASK to ensure writes take effect, preventing timing/counting gaps in privileged-mode operation. Performed targeted validation and code review, aligning with architectural CSR handling and enabling more reliable OS timing, performance measurements, and test reproducibility.
February 2025
1 Commits • 1 Features
Feb 1, 2025February 2025 — OpenXiangShan/GEM5: Focused on instrumentation to improve memory subsystem performance visibility. Delivered Memory Cache MSHR Bandwidth Analytics, adding counters mshrinsert, multimshr, and multicacheline to quantify how MSHRs affect memory bandwidth. This enables data-driven cache optimization and deeper insight into cache access patterns. Commit reference: mem-cache: Add cache mshr stats (#276) (5944748d95bb3f04c101438e28655bfed5f47790). No major bugs fixed this month based on the tracked work. Overall impact includes improved observability for MSHR-related traffic, informing targeted performance improvements and capacity planning. Technologies/skills demonstrated include low-level memory subsystem instrumentation, performance data modeling, and disciplined code contribution.
1 Commits • 1 Features
Feb 1, 2025February 2025 — OpenXiangShan/GEM5: Focused on instrumentation to improve memory subsystem performance visibility. Delivered Memory Cache MSHR Bandwidth Analytics, adding counters mshrinsert, multimshr, and multicacheline to quantify how MSHRs affect memory bandwidth. This enables data-driven cache optimization and deeper insight into cache access patterns. Commit reference: mem-cache: Add cache mshr stats (#276) (5944748d95bb3f04c101438e28655bfed5f47790). No major bugs fixed this month based on the tracked work. Overall impact includes improved observability for MSHR-related traffic, informing targeted performance improvements and capacity planning. Technologies/skills demonstrated include low-level memory subsystem instrumentation, performance data modeling, and disciplined code contribution.
February 2025
January 2025
1 Commits • 1 Features
Jan 1, 2025January 2025 monthly summary focusing on the OpenXiangShan/GEM5 work. The primary delivered feature is the RISC-V sv48 Address Usage Warning System, which adds a non-intrusive warning mechanism to detect potential sv48 address usage and emit warnings without altering the translation process. This supports debugging and helps prevent deadlocks by identifying sv48-related patterns early. The work is tracked under commit 4979689920d0bc6cf54932ede872722216815bb0 ("arch-riscv: add sv48 warning message (#262)"). No other major bugs fixed in this repo this month.
January 2025
1 Commits • 1 Features
Jan 1, 2025January 2025 monthly summary focusing on the OpenXiangShan/GEM5 work. The primary delivered feature is the RISC-V sv48 Address Usage Warning System, which adds a non-intrusive warning mechanism to detect potential sv48 address usage and emit warnings without altering the translation process. This supports debugging and helps prevent deadlocks by identifying sv48-related patterns early. The work is tracked under commit 4979689920d0bc6cf54932ede872722216815bb0 ("arch-riscv: add sv48 warning message (#262)"). No other major bugs fixed in this repo this month.
December 2024
4 Commits • 2 Features
Dec 1, 2024December 2024: Concrete progress on testing, benchmarking, and correctness in GEM5. Implemented default Difftest instruction tracing to enhance test coverage and analysis, added a configurable Cliff workload benchmark to GEM5 for realistic performance evaluation, fixed LSQ-related bank conflict handling to remove stale warnings, and corrected TLB prefetch address calculation in RISC-V to ensure accurate prefetch behavior. These changes collectively improve test reliability, benchmarking realism, and architectural correctness, enabling better performance analysis and faster issue diagnosis.
4 Commits • 2 Features
Dec 1, 2024December 2024: Concrete progress on testing, benchmarking, and correctness in GEM5. Implemented default Difftest instruction tracing to enhance test coverage and analysis, added a configurable Cliff workload benchmark to GEM5 for realistic performance evaluation, fixed LSQ-related bank conflict handling to remove stale warnings, and corrected TLB prefetch address calculation in RISC-V to ensure accurate prefetch behavior. These changes collectively improve test reliability, benchmarking realism, and architectural correctness, enabling better performance analysis and faster issue diagnosis.
December 2024
November 2024
4 Commits • 2 Features
Nov 1, 2024November 2024 (OpenXiangShan/GEM5) delivered targeted memory subsystem improvements and expanded architecture testing, enhancing performance, stability, and validation coverage. Key changes include cache resource management to cap L1 tag read ports with new debug flags and LSQ rescheduling on tag read failures; xsstream prefetcher bug fixes and kmh_align enablement with a security-context check; refined RISC-V L2 TLB refresh logic for non-zero VPN/ASID to improve memory-management stability; and added GEM5 RVH architecture testing support with a new CI test job, updated configurations, and a script for RVH checkpoint simulation.
November 2024
4 Commits • 2 Features
Nov 1, 2024November 2024 (OpenXiangShan/GEM5) delivered targeted memory subsystem improvements and expanded architecture testing, enhancing performance, stability, and validation coverage. Key changes include cache resource management to cap L1 tag read ports with new debug flags and LSQ rescheduling on tag read failures; xsstream prefetcher bug fixes and kmh_align enablement with a security-context check; refined RISC-V L2 TLB refresh logic for non-zero VPN/ASID to improve memory-management stability; and added GEM5 RVH architecture testing support with a new CI test job, updated configurations, and a script for RVH checkpoint simulation.
October 2024
1 Commits
Oct 1, 2024October 2024: Delivered a critical bug fix for RISC-V SIE interrupt handling in OpenXiangShan/GEM5, improving interrupt masking and propagation across privilege levels and virtual mode, and enhancing overall system reliability in simulated environments.
1 Commits
Oct 1, 2024October 2024: Delivered a critical bug fix for RISC-V SIE interrupt handling in OpenXiangShan/GEM5, improving interrupt masking and propagation across privilege levels and virtual mode, and enhancing overall system reliability in simulated environments.
October 2024
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Quality Metrics
Correctness83.0%
Maintainability81.6%
Architecture80.8%
Performance74.2%
AI Usage25.4%
Skills & Technologies
Programming Languages
BashC++MarkdownPythonScalaShellYAML
Technical Skills
Benchmark ExecutionBug FixingBuild SystemsC++ DevelopmentC++ developmentCI/CDCPU ArchitectureCPU SimulationCache CoherenceCache PrefetchingCache SimulationCode RefactoringConfiguration ManagementContinuous IntegrationDebugging
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