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| author | Vivian Wang <wangruikang@iscas.ac.cn> | 2026-06-25 14:34:15 +0800 |
|---|---|---|
| committer | Paul Walmsley <pjw@kernel.org> | 2026-06-25 11:41:15 -0600 |
| commit | 0fa749771993033befb9dda60b023782cb5fd2d9 (patch) | |
| tree | ee12479e94febb882c359cf1961d8ca2ba674fe9 /arch | |
| parent | c75597caada080effbfbc0a7fb10dc2a3bb543ad (diff) | |
| download | linux-2.6-0fa749771993033befb9dda60b023782cb5fd2d9.tar.gz linux-2.6-0fa749771993033befb9dda60b023782cb5fd2d9.zip | |
riscv: Raise default NR_CPUS for 64BIT to 256
SpacemiT has already produced a 80-core RVA23 RISC-V server [1], and
going further back, the dual-socket SG2042-based Sophgo Pisces has 128
cores (although that had some issues achieving mainline support).
Therefore, an NR_CPUS of 64 is not enough.
Raise default NR_CPUS to 256 for 64BIT (when !RISCV_SBI_V01, since very
old firmware can't support more than 64 cores). The number was picked as
a power of two that is at least double the known max. I believe this
should be the right balance between not wasting too much memory and not
having to touch this too often.
Ubuntu has already been shipping NR_CPUS=512 for riscv64. We have also
been testing NR_CPUS=256 internally at ISCAS and found negligible
performance impact and no ill effects.
Reported-by: Lufei Zheng <lufei.zheng@spacemit.com>
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1140651 # [1]
Suggested-by: Han Gao <gaohan@iscas.ac.cn>
Signed-off-by: Vivian Wang <wangruikang@iscas.ac.cn>
Link: https://patch.msgid.link/20260625-riscv-more-nr-cpus-v1-1-5da8c72b9269@iscas.ac.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/riscv/Kconfig | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 3f0a647218e4..c0a6992933e4 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -454,7 +454,8 @@ config NR_CPUS range 2 32 if RISCV_SBI_V01 && 32BIT range 2 64 if RISCV_SBI_V01 && 64BIT default "32" if 32BIT - default "64" if 64BIT + default "64" if RISCV_SBI_V01 && 64BIT + default "256" if !RISCV_SBI_V01 && 64BIT config HOTPLUG_CPU bool "Support for hot-pluggable CPUs" |