Lock-less Zero-copy Messaging for LTE Modems
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Solution Overview
Problem
In LTE wireless communication systems, the use of a single modem board with multiple cores faces latency spikes due to the non-lockless nature of the Linux protocol stack, which can cause the LTE L2 scheduler to break down, especially in multi-cell configurations where real-time and non-real-time processes share the same operating system instance.
Innovation Solution
A lock-less, zero-copy, non-blocking messaging scheme is implemented using a circular buffer and kernel-to-user-space mapped buffer descriptors, allowing data packets to be processed without crossing the user-kernel boundary, thus avoiding the Linux protocol stack and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Linux protocol stack is used for data plane functions on a multi-core processor, then general-purpose operating system support is achieved, but unbounded latency spikes occur due to lock contention between real-time and non-real-time processes
Solution Approach 1:
The patent segments the operating system into two separate instances: a control plane OS for non-real-time functions and a data plane OS for real-time functions. Each OS instance runs independently on designated cores, eliminating lock contention between different process types while maintaining comprehensive OS support for both control and data plane operations.
2Adaptability or versatility
If multiple modem boards are used to support multi-cell configurations, then each cell can be properly supported, but system complexity and cost increase
Solution Approach 1:
The patent merges multiple cell support capabilities onto a single modem board by implementing a multi-core processor architecture where each core can handle a separate cell. The data plane OS is configured to support multiple cells simultaneously, eliminating the need for multiple separate modem boards while maintaining full multi-cell functionality.
3Adaptability or versatility
If data packets cross the user-kernel boundary using the Linux protocol stack, then standard networking protocols are supported, but data copying and lock acquisition cause processing delays
Solution Approach 1:
The patent extracts the critical data plane packet processing path from the Linux protocol stack to eliminate lock contention and data copying. A dedicated data plane OS instance handles real-time packet processing directly without requiring locks or protocol stack traversal, while the control plane OS maintains standard protocol support for non-real-time operations.
4Reliability
If locks are used for buffer access in a multi-core environment, then data consistency is maintained, but real-time processing is blocked by non-real-time processes acquiring locks
Solution Approach 1:
The patent segments buffer access into separate address spaces for control plane and data plane operations. The data plane OS accesses buffers in its own address space without requiring locks, while the control plane OS manages buffers in a separate space. This segmentation maintains data consistency through address space isolation while eliminating lock-induced delays for real-time processing.
Data Source
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AI summary
A computer-implemented system and method for a lock-less, zero data copy messaging mechanism in a multi-core processor for use on a modem in a telecommunications network are described herein. The method includes, for each of a plurality of processing cores, acquiring a kernel to user-space (K-U) mapped buffer and corresponding buffer descriptor, inserting a data packet into the buffer; and inserting the buffer descriptor into a circular buffer. The method further includes creating a frame descriptor containing the K-U mapped buffer pointer, inserting the frame descriptor onto a frame queue specified by a dynamic PCD rule mapping IP addresses to frame queues, and creating a buffer descriptor from the frame descriptor.