arXiv subjects

Bojie Li

Publications and source records attributed to Bojie Li.

22 records · Page 2Linked to original sources

arXiv2026

Tiara: A Programmable Line-Rate ISA for Remote Memory Access

RDMA one-sided verbs are the natural primitive for memory disaggregation, but they require the client to supply the exact remote address. The 1-RTT performance breaks down when the target address depends on data that must first be read from remote memory, a pattern we call the Indirection Wall. Indirection is pervasive: graph traversals follow pointers hop by hop, address translation walks multi-level page tables, distributed coordination requires conditional multi-host logic, and disaggregated LLM inference must resolve paged KV caches through block-table lookups. Each level of indirection costs one sequentially dependent network round-trip, yet offloading to existing RDMA NICs either consumes remote CPU cycles or has limited throughput. We present Tiara, a compact, statically verifiable instruction set that executes on the memory-side NIC. Tiara operators are pre-registered programs, analogous to eBPF programs in the kernel, that resolve indirection locally, collapsing multi-RTT dependent chains into a single round-trip. On an FPGA-based prototype, Tiara reduces 10-hop graph-traversal latency by 2.85x over one-sided RDMA while sustaining 3.4x higher throughput, cuts page-table walk latency by 62%, reduces uncontended distributed-lock latency by 2.9x, achieves 2.8x throughput for disaggregated PagedAttention at 8 KB blocks, and 1.88x MoE expert-gather latency at 32 experts.

cs.AR↗

arXiv2026

OpenURMA: A Clean-Room Open Implementation of the Unified Bus Protocol

Modern datacenter RDMA is bottlenecked at the network interface, not the wire. A NIC running RoCE or InfiniBand holds per-connection state for every (application, remote-endpoint) pair - hundreds of megabytes at 1024-application fanout - and pays a four-traversal PCIe round trip on a 64-byte operation, inflating latency an order of magnitude beyond the wire. Both follow from the Queue Pair over PCIe abstraction RDMA inherits from InfiniBand. Huawei's Unified Bus (UB), a public 2025 specification, changes the abstraction: it decouples per-application endpoint state from per-host transport state so connection context grows additively, exposes ordering as opt-in, and reaches remote memory through native CPU load/store to an on-chip-bus controller. UB ships in Huawei's closed Ascend 950 silicon. OpenURMA is the first clean-room open implementation of UB's transport and transaction layers, realised at three tiers - synthesisable RTL on Alveo U50, a cycle-level two-node SystemC simulator, and a gem5 full-system scaffold - each with a matched OpenRoCE (RoCEv2 RC) baseline. The contribution is the implementation, harness, and controlled comparison closed silicon does not admit. On the canonical 64-byte remote fetch - LOAD on UB-spec Sec.8.3, READ on RoCEv2 RC - UB's load/store path delivers ~500 ns end-to-end, 4.37x below the matched baseline (2186 ns), sustains 2.80x higher throughput, and fits in ~14% of a U50's LUTs.

cs.AI↗

arXiv2026

Sema: Semantic Transport for Real-Time Multimodal Agents

Real-time multimodal agents transport raw audio and screenshots using networking stacks designed for human receivers, which optimize for perceptual fidelity and smooth playout. Yet agent models act as event-driven processors with no inherent sense of physical time, consuming task-relevant semantics rather than reconstructing signals in real time. This fundamental difference shifts the transport goal from the technical problem of signal fidelity (Shannon-Weaver Level A) to the semantic problem of meaning preservation (Level B). This mismatch imposes significant overhead. In visual pipelines, screenshot upload accounts for over 60% of end-to-end action latency on constrained uplinks, and in voice pipelines, conventional transport carries massive redundancy, sending 43-64x more data than needed to maintain task accuracy. We present Sema, a semantic transport system that combines discrete audio tokenizers with a hybrid screen representation (lossless accessibility-tree or OCR text, plus compact visual tokens) and bursty token delivery that eliminates jitter buffers. In simulations under emulated WAN conditions, Sema reduces uplink bandwidth by 64x for audio and 130-210x for screenshots while preserving task accuracy within 0.7 percentage points of the raw baseline.

cs.MM↗

arXiv2023

NP-RDMA: Using Commodity RDMA without Pinning Memory

Remote Direct Memory Access (RDMA) has been haunted by the need of pinning down memory regions. Pinning limits the memory utilization because it impedes on-demand paging and swapping. It also increases the initialization latency of large memory applications from seconds to minutes. To remove memory pining, existing approaches often require special hardware which supports page fault, and still have inferior performance. We propose NP-RDMA, which removes memory pinning during memory registration and enables dynamic page fault handling with commodity RDMA NICs. NP-RDMA does not require NICs to support page fault. Instead, by monitoring local memory paging and swapping with MMU-notifier, combining with IOMMU/SMMU-based address mapping, NP-RDMA efficiently detects and handles page fault in the software with near-zero additional latency to non-page-fault RDMA verbs. We implement an LD_PRELOAD library (with a modified kernel module), which is fully compatible with existing RDMA applications. Experiments show that NP-RDMA adds only 0.1{\sim}2 μs latency under non-page-fault scenarios. Moreover, NP-RDMA adds only 3.5{\sim}5.7 μs and 60 μs under minor or major page faults, respectively, which is 500x faster than ODP which uses advanced NICs that support page fault. With non-pinned memory, Spark initialization is 20x faster and the physical memory usage reduces by 86% with only 5.4% slowdown. Enterprise storage can expand to 5x capacity with SSDs while the average latency is only 10% higher. To the best of our knowledge, NP-RDMA is the first efficient and application-transparent software approach to remove memory pinning using commodity RDMA NICs.

cs.NI↗