Hakbeom Jang;Younghoon Min;Dongha Yoon;Hane Yie;Hoshik Kim;Jongryool Kim
{"title":"JBOC: Just a Bunch of CXL-Enabled SSDs for Resource-Efficient LLM Checkpointing","authors":"Hakbeom Jang;Younghoon Min;Dongha Yoon;Hane Yie;Hoshik Kim;Jongryool Kim","doi":"10.1109/LCA.2026.3676331","DOIUrl":"https://doi.org/10.1109/LCA.2026.3676331","url":null,"abstract":"The rapid growth of Large Language Models (LLMs) has pushed training systems to rely on memory sharding and offloading, introducing substantial data movement overhead. This is further exacerbated by frequent checkpointing, where training states must traverse multiple software and hardware layers. Such a process creates a critical performance bottleneck, as traditional host-centric hierarchies struggle to handle the massive data movement required for high-frequency, fault-tolerant checkpointing. In this paper, we introduce JBOC, an in-device processing architecture leveraging CXL-enabled SSDs that fuses optimizer updates and checkpointing into a single, unified operation. By offloading massive footprint optimizer updates and executing these fused tasks directly within internal computational units, JBOC achieves highly efficient checkpointing as persistence is handled during the update pipeline. This offloaded approach allows training states to remain within device-side resources, bypassing the host-side resource hierarchy and effectively isolating the host from heavy storage traffic. We validate JBOC on commercial CXL platforms from Marvell and SK Hynix. Our evaluation achieves up to a <inline-formula><tex-math>$4.40,times$</tex-math></inline-formula> speedup under per-iteration checkpointing. Compared to ZeRO-Offload, JBOC delivers comparable throughput while checkpointing <inline-formula><tex-math>$10,times$</tex-math></inline-formula> more frequently. Furthermore, JBOC outperforms both ZeRO-Offload and ZeRO-Infinity in memory-constrained scenarios, demonstrating its robustness when host resources are limited.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"182-185"},"PeriodicalIF":1.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148003648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Wafer-Scale GPU Memory Pool With In-Package Optics for Enhanced Capacity and Bandwidth","authors":"Khakim Akhunov;Aakash Patel;Robert Kleijnen;Julien Ryckaert;James Myers;Dwaipayan Biswas","doi":"10.1109/LCA.2026.3696219","DOIUrl":"https://doi.org/10.1109/LCA.2026.3696219","url":null,"abstract":"The escalating demands of modern AI applications push the limits of conventional GPU memory systems, where high-bandwidth memory (HBM) architectures face critical challenges in scalability and bandwidth efficiency. We propose a wafer-scale system integrating photonic interconnects to decouple GPU compute from memory, addressing capacity and bandwidth limitations of conventional HBM-based architectures. We develop an analytical framework, HBM-pool, blending in-package optical I/O (OIO) parameters with GPU memory traffic for high-density nodes. The system-technology co-optimization (STCO) study shows that 300 mm wafer-scale disaggregation with OIO can achieve a 4× increase in memory capacity and reduce bandwidth bottlenecks up to 8× compared to a 2.5D electrically packaged node, enabling larger training/inference and improving latency.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"230-234"},"PeriodicalIF":2.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148442455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dusol Lee;Taehyung Lee;Hanseon Lee;Nam Sung Kim;Jihong Kim
{"title":"MMC: Metadata Migration for Efficient Memory Management in CXL DRAM Systems","authors":"Dusol Lee;Taehyung Lee;Hanseon Lee;Nam Sung Kim;Jihong Kim","doi":"10.1109/LCA.2026.3687345","DOIUrl":"https://doi.org/10.1109/LCA.2026.3687345","url":null,"abstract":"CXL-DRAM enables cost-efficient memory expansion in data-center servers, but introduces new challenges for operating system memory management. In particular, large in-kernel metadata structures can occupy a significant portion of DDR-DRAM, reducing the space available for application data and increasing accesses to slower CXL-DRAM. Placing all metadata in CXL-DRAM frees DDR-DRAM space but can cause severe tail latency due to inefficient memory reclamation. We propose <monospace>MMC</monospace>, a hot–cold metadata migration mechanism that balances application performance and reclamation efficiency by dynamically placing metadata across DDR-DRAM and CXL-DRAM. Our results show that <monospace>MMC</monospace> improves throughput while reducing tail latency across diverse workloads.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"166-169"},"PeriodicalIF":2.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148478929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohammad M. Gharaguzlo;Mohammadamin Ajdari;Hossein Asadi
{"title":"Smart Prediction of I/O Accesses in Enterprise Workloads to Accelerate Data Serving During Array Reconstruction","authors":"Mohammad M. Gharaguzlo;Mohammadamin Ajdari;Hossein Asadi","doi":"10.1109/LCA.2026.3669450","DOIUrl":"https://doi.org/10.1109/LCA.2026.3669450","url":null,"abstract":"Storage systems in mission-critical environments require steady high performance all the time. When a <italic>Solid-State Drive</i> (SSD) fails within a disk array, the array reconstruction starts and therefore, serving the application I/O request rate slows down. As our <italic>first</i> contribution, we reveal that SSD arrays suffer from up to 3.3× drop of <italic>I/O per Second</i> (IOPS) of serving enterprise workloads during SSD array reconstruction. To mitigate the array reconstruction problem, existing studies modify RAID algorithms, which make them inapplicable to many deployed SAN storage systems. Others propose predicting hot workload accesses during array reconstruction, and serving those addresses from a faster device. Unfortunately, we observe that such approaches mainly focus on short history, or have improper weight assignment for long history tracking, thus suffer from incomplete access predictions, and low acceleration opportunities. As the <italic>second</i> contribution, we propose a novel I/O history pattern analysis, which applies proper weights for short- and long-term to maximize detection of repeated workload accesses during array reconstruction. We implement our proposed method and evaluate its effectiveness on a real system using enterprise workload I/O traces. Our proposed method predicts 80% more hot requests compared to state-of-art, which enables <italic>27% higher average IOPS</i> during array reconstruction.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"101-104"},"PeriodicalIF":1.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147557649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Dicemite: Scaling Shared-Memory Isolation for Highly Consolidated FaaS Workers","authors":"Seonggyu Han;Jongmin Shin;Daehoon Kim","doi":"10.1109/LCA.2026.3688492","DOIUrl":"https://doi.org/10.1109/LCA.2026.3688492","url":null,"abstract":"Function-as-a-Service (FaaS) workers heavily consolidate and multiplex many short-lived functions, intensifying contention for shared last-level cache (LLC) and memory bandwidth (BW) and inflating tail latency. Existing cache/bandwidth managers largely assume long-lived workloads that can be profiled and controlled per entity, assumptions that break under extreme function multiplicity, bursty arrivals, and the small, fixed number of hardware-enforceable control domains. We present <monospace>Dicemite</monospace>, a role-based shared-memory resource manager for FaaS workers, where a <italic>role</i> is a bounded, hardware-enforceable abstraction of shared-memory pressure. <monospace>Dicemite</monospace> scales by admitting only the high-impact subset, summarizing their LLC/BW pressure into a small number of roles, and allocating/enforcing budgets at role granularity while leaving the long tail as best-effort. Across synthetic load sweeps and trace-driven replays, <monospace>Dicemite</monospace> improves sustainable throughput and reduces end-to-end tail latency.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"170-173"},"PeriodicalIF":1.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148003629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"FeatureBleed: Inferring Private Enriched Attributes From Sparsity-Optimized AI Accelerators","authors":"Darsh Asher;Farshad Dizani;Joshua Kalyanapu;Rosario Cammarota;Aydin Aysu;Samira Mirbagher Ajorpaz","doi":"10.1109/LCA.2026.3666823","DOIUrl":"https://doi.org/10.1109/LCA.2026.3666823","url":null,"abstract":"Backend enrichment deployed in sensitive domains such as product recommendation pipelines, healthcare, and finance, where models are trained on confidential data and retrieve private features whose values influence inference behavior while remaining hidden from the API caller. This paper presents the first <italic>hardware-level backend retrieval data-stealing attack</i>, showing that accelerator optimizations designed for performance can directly undermine data confidentiality and bypass state-of-the-art privacy defenses. Our attack, <sc>FeatureBleed</small>, exploits <italic>zero-skipping</i> in AI accelerators to infer private backend-retrieved features solely through end-to-end timing, without relying on power analysis, DVFS manipulation, or shared-cache side channels. We evaluate <sc>FeatureBleed</small> on three datasets spanning medical and non-medical domains—Texas-100X (clinical records), OrganAMNIST (medical imaging), and Census-19 (socioeconomic data). We further evaluate <sc>FeatureBleed</small> across three hardware backends (Intel AVX, Intel AMX, and NVIDIA A100) and three model architectures (DNNs, CNNs, and hybrid CNN–MLP pipelines), demonstrating that the leakage generalizes across CPU and GPU accelerators, data modalities, and application domains, with an adversarial advantage of up to <bold>98.87</b> pp. Finally, we identify the root cause of the leakage as sparsity-driven zero-skipping in modern hardware. We quantify the privacy–performance–power trade-off: disabling zero-skipping increases Intel AMX’s per-operation energy by up to <bold>25%</b> and incurs <bold>100%</b> performance overhead. We propose a padding-based defense that masks timing leakage by equalizing responses to the worst-case execution time, achieving protection with only <bold>7.24%</b> average performance overhead and no additional power cost is now widely.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"77-80"},"PeriodicalIF":2.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148478829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Reducing LLM Inference Memory Bandwidth via Frequent Exponent Value Encoding","authors":"Maxwell Michalec;Swamit Tannu;Gurindar Sohi","doi":"10.1109/LCA.2026.3671166","DOIUrl":"https://doi.org/10.1109/LCA.2026.3671166","url":null,"abstract":"We consider the issue of the memory bandwidth required for the transfer of weights of an LLM between the memory and the processor (CPU or GPU). Observing that a few exponent values dominate for FP8 and BF16 floating-point formats, we propose an alternate (compressed) representation and storage of the exponents in memory, and a design for reconstructing the full, exact weight values in the processor. The proposed approach reduces the memory bandwidth needed by up to 10% and 30% for LLMs using weight in FP8 and BF16 formats, respectively, without changing any of the computation carried out by the original LLM inference software.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"85-88"},"PeriodicalIF":2.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148479224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"An Operand Divergence-Aware All-Bank PIM Architecture for Sparse Attention","authors":"Soojin Hwang;Sanghyeon Lee;Juhyun Lee;Jaehyuk Huh","doi":"10.1109/LCA.2026.3684216","DOIUrl":"https://doi.org/10.1109/LCA.2026.3684216","url":null,"abstract":"Processing-in-memory (PIM) architectures leverage all-bank execution to provide high internal bandwidth for memory-bound operations. However, synchronized control across banks fundamentally conflicts with the irregular access patterns of sparse workloads, where operand divergence requires banks to access different row or column addresses. We propose a novel divergence-aware all-bank PIM architecture that resolves operand-level data divergence. Our design enables each bank to dynamically access distinct rows or columns under a shared command, allowing sparse execution without sacrificing bank-level parallelism. We apply this architecture to accelerate large language models with dynamic KV-cache filtering with unstructured token-level sparsity. The simulation results show that the proposed design achieves an average 6.6× speedup over dense all-bank PIM.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"158-161"},"PeriodicalIF":1.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147796055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Enabling Computation and Communication Overlap in PIMs for On-Device LLM Inference","authors":"Siu Jeong;Suhwan Kim;Changyong Eom;Jaehyuk Huh","doi":"10.1109/LCA.2026.3676795","DOIUrl":"https://doi.org/10.1109/LCA.2026.3676795","url":null,"abstract":"DRAM-based processing-in-memory (PIM) exploits all-bank execution to accelerate memory-bound workloads, but limited PIM capacity makes runtime data movement unavoidable and often performance-critical. Existing PIM architectures tightly couple computation and memory access across all banks, serializing computation and data transfer and limiting opportunities to hide communication latency. This paper proposes a bank-level computation–communication overlap mechanism that selectively assigns a subset of bank resources for communication, enabling concurrent data transfer without disrupting ongoing computation while preserving the unified control model of all-bank PIM. Evaluations on mixture-of-experts (MoE) and multi–small language model (multi-SLM) inference workloads using a simulated LPDDR5-based PIM system show execution time reductions of up to 19% and 16%, respectively, along with consistently improved channel bandwidth utilization compared to all-bank and channel-level overlap baselines.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"126-129"},"PeriodicalIF":1.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147665383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Untangling the Low Accuracy of the Entangling Instruction Prefetcher","authors":"Vedant Kalbande;Biswabandan Panda;Alexandra Jimborean;Alberto Ros","doi":"10.1109/LCA.2026.3676273","DOIUrl":"https://doi.org/10.1109/LCA.2026.3676273","url":null,"abstract":"The Entangling Instruction Prefetcher (EIP) is a state-of-the-art mechanism designed to improve instruction-fetch timeliness. While earlier studies report an average prefetch accuracy of 72% and as high as 91%, more recent evaluations using different methodologies—most notably the gem5 simulator—report lower accuracies of 44% on average and even below 30%. This work aims to shed light on this controversy by providing a robust and faithful open-source implementation within the gem5 simulation framework. In addition, we analyze several design choices that influence EIP's accuracy and performance highlighting common pitfalls when porting EIP across simulators. In our experiments, using the same benchmarks as prior studies, our gem5 version of EIP achieves an average prefetch accuracy of 64.35%, demonstrating that its accuracy remains stable across the simulators.","PeriodicalId":51248,"journal":{"name":"IEEE Computer Architecture Letters","volume":"25 1","pages":"130-133"},"PeriodicalIF":1.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147665455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}