Linux's Early Boot-Time Physical Memory Allocator Sees Big Speed-Up: ~268s To ~50ms
Linux kernel 7.4 introduces memblock improvements, including a binary search optimization for the early boot-time physical memory allocator, reducing retrieval time from 268s to 50ms.
Intelligence analysis by Qwen 2.5 (3B)
Linux kernel 7.4 speeds up the early boot-time physical memory allocator with a binary search optimization, cutting retrieval time from 268 seconds to 50 milliseconds.
The Linux kernel's early boot-time memory allocator used to take a long time to find memory regions. Now, it can do it much faster using a binary search, like how you might quickly find a book in a library by checking the middle shelf first.
Analysis
{"# Tarun Sahu's Observation":"Google engineer Tarun Sahu noticed that the mm/memblock.c code was using a linear search for finding candidate regions, which was inefficient under heavy fragmentation conditions. He suggested using a binary search to improve performance.","# Binary Search Implementation":"The binary search implementation in memblock_add_range() and memblock_isolate_range() functions reduces the worst-case complexity from O(N) to O(N log N), resulting in a significant speedup.","# Impact on Kernel Handover (KHO)":"The binary search optimization reduces the KHO memory retrieval time from around 238 seconds to around 50 milliseconds, demonstrating the practical benefits of the change."}
Key points
- Linux kernel 7.4 introduces memblock improvements
- Binary search optimization for early boot-time physical memory allocator
- Reduces retrieval time from 268 seconds to 50 milliseconds
- Improves performance in environments with heavy fragmentation and Kernel Handover (KHO) usage
- Optimization was sent out as part of the memblock pull request for the Linux 7.4 kernel
This optimization can help reduce boot times and improve the overall performance of Linux systems, especially in environments with high fragmentation and the use of the Kernel Handover functionality.
While the binary search optimization is a significant improvement, there could be potential issues if the binary search algorithm encounters a situation where the memory regions are not evenly distributed.