On 25 May 2015, at 23:29, Arnd Bergmann <[email protected]> wrote: > On Monday 25 May 2015 19:47:15 Catalin Marinas wrote: >> On 25 May 2015, at 13:01, Jungseok Lee <[email protected]> wrote: >>>> Could the stack size be reduced to 8KB perhaps? >>> >>> I guess probably not. >>> >>> A commit, 845ad05e, says that 8KB is not enough to cover SpecWeb benchmark. >> >> We could go back to 8KB stacks if we implement support for separate IRQ >> stack on arm64. It's not too complicated, we would have to use SP0 for >> (kernel) threads >> and SP1 for IRQ handlers. > > I think most architectures that see a lot of benchmarks have moved to > irqstacks at some point, that definitely sounds like a useful idea, > even if the implementation turns out to be a bit more tricky than > what you describe.
Of course, it's more complicated than just setting up two stacks (but I'm away for a week and writing from a phone). We would need to deal with the initial per-CPU setup, rescheduling following an IRQ, CPU on following power management and maybe other issues. However, the architecture helps us a bit by allowing both SP0 and SP1 to be used at EL1. > There are a lot of workloads that would benefit from having lower > per-thread memory cost. If we keep the 16KB stack, is there any advantage in a separate IRQ one (assuming that we won't overflow 16KB)? Catalin-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
