maxcpus=1?

Posted Jun 10, 2025 20:06 UTC (Tue) by marcH (subscriber, #57642)
Parent article: An end to uniprocessor configurations

This was probably too obvious to even mention but just to be on the safe side... will maxcpus=1 still be available? It's very useful for testing purposes (finding races etc.)

maxcpus=1?

Posted Jun 11, 2025 6:42 UTC (Wed) by tamiko (subscriber, #115350) [Link] (1 responses)

This should continue to work. The patch set is about removing the CONFIG_SMP configuration option.

maxcpus=1?

Posted Jun 11, 2025 9:47 UTC (Wed) by arnd (subscriber, #8866) [Link]

Not even that, the series specifically removes the special case for CONFIG_SMP=n in the scheduler, not anywhere else.

You can still build a kernel with SMP disabled, and it will still use the trivial implementation of per-cpu data, spinlocks, smp barriers etc, which is where most of the performance and size advantages are for non-SMP builds.

There is currently no way to build an SMP kernel for a lot of the older embedded architectures that lack the required CPU instructions or the irqchip for SMP: ARMv5, most MIPS32r2, PowerPC8xx, m68k, SH3/SH4, ARCompact, microblaze, nios2, and xtensa.