Linux Kernel Increases Default RISC-V CPU Core Count
The upcoming Linux 7.2-rc2 kernel release introduces a significant adjustment for the RISC-V architecture, raising the default supported CPU core count from 64 to 256.
Beijing, China – The Linux kernel's mainline has received a notable enhancement for the RISC-V architecture, with the upcoming release of Linux 7.2-rc2 set to more than quadruple the default number of supported CPU cores.
This change, integrated as part of RISC-V patches, addresses the growing capabilities of RISC-V server hardware. Companies like SpacemiT have developed 80-core RVA23 standard servers, and previous dual-socket servers based on Sophgo's SG2042 chip feature 128 cores, necessitating an increase beyond the original 64-core default.
The kernel configuration parameter 'NR_CPUS' dictates static memory allocations within the kernel. The new threshold of 256 was chosen as a power of two at least double the known maximum core count, balancing memory usage with future needs. Other distributions, such as Ubuntu, already utilize higher NR_CPUS values for RISC-V, and internal testing indicated negligible performance impact.
While the new default remains conservative compared to architectures like x86_64 (up to 8192 cores) and ARM64 (512 cores), it signifies Linux's preparation for RISC-V's expansion into higher-core-count server markets. The modification was accepted by kernel maintainer Linus Torvalds, indicating a low-risk integration.