llm-batch: A Practical Solution for Accelerating LLM Batch Processing Tasks with C++ Multithreading

llm-batch is an open-source project that addresses the bottlenecks in inference efficiency and system throughput of large language models (LLMs). It uses C++ multithreading technology to parallelize batch processing tasks, and improves hardware resource utilization and system throughput through mechanisms like thread pools. It provides a scalable solution for production environments and is suitable for various scenarios such as server-side inference and offline data processing.

LLM inference is a computationally intensive task, facing challenges such as high concurrent request pressure (serial processing delay increases linearly), unbalanced resource utilization (single thread cannot fully utilize multi-core hardware), and trade-offs between cost and efficiency (in cloud service scenarios, latency affects user experience while throughput determines the number of users served per unit cost). Batch processing technology is a classic solution to these problems, and llm-batch combines the high-performance features of C++ to build a lightweight batch processing framework.

llm-batch is developed based on C++ and uses the thread pool pattern as its core: 1. Thread reuse reduces the overhead of creation and destruction; 2. The task queue decouples production and consumption, supporting asynchronous processing; 3. Fine-grained concurrency control allows dynamic adjustment of the number of threads to balance multi-core utilization and context switching overhead.

1. Task Scheduling and Load Balancing: Dynamically evaluate thread load and intelligently assign tasks of different complexities to avoid thread overload or idleness; 2. Memory Management and Resource Reuse: Use object pools to reuse data structures (input tensors, caches, etc.) during inference, reducing memory allocation overhead and fragmentation; adopt zero-copy design and share data through smart pointers/reference counting; 3. Synchronization Primitives and Thread Safety: Use mutexes, condition variables, and atomic operations to ensure data integrity and thread safety in high-concurrency scenarios.

llm-batch is suitable for: 1. Server-side Inference Engine: As the core of the request processing layer, it aggregates user requests into batches for parallel processing, improving API service QPS; 2. Offline Data Processing Pipeline: Accelerates batch text processing tasks such as document summarization and sentiment analysis, reducing processing time; 3. Model Evaluation and Benchmarking: Parallelizes large-scale model evaluation tasks to speed up the acquisition of experimental results.

1. Thread Count Selection: It is recommended to set it to 1-2 times the number of CPU cores to avoid context switching caused by too many threads; 2. Batch Size Trade-off: Online services need to balance throughput and latency; 3. Memory Bandwidth Bottleneck: Can be alleviated by model quantization (INT8/INT4) to reduce memory usage, or by using a hierarchical loading strategy.

llm-batch solves the engineering problems of LLM inference through C++ multithreading batch processing technology, improving throughput and resource utilization. In the future, we can expect batch processing solutions optimized for hardware such as GPU/NPU, as well as integration with technologies like dynamic batch processing and continuous batch processing. Efficient and scalable inference infrastructure is an important cornerstone for the popularization of LLMs.