rcu_sched stall OR kernel panic on PowerEdge R640

[Quazz]

@Sebastian-Roth

There are kernel flags to disable SMP if necessary, so I think it’s pretty safe to compile with MAXSMP. Just my opinion of course; without a diverse test fleet it’s hard to say for sure since kernels can always have bugs or unforeseen interactions. But that would be true for any change we make.

I can’t find anything googling about stalls/problems with MAXSMP either. Only some people on embedded systems who want to reduce the size of their kernel, but that’s a targetted compile anyway.

There will be more and more systems entering the floor with more than 8 cores (our current NR_CPU value) given the recent CPU releases as well, so at the very least that number could use a bump.

[Sebastian Roth]

@Quazz said in rcu_sched stall OR kernel panic on PowerEdge R640:

I can’t find anything googling about stalls/problems with MAXSMP either. Only some people on embedded systems who want to reduce the size of their kernel, but that’s a targetted compile anyway.

Ok, you and George have convinced me this is most probably not going to cause us much trouble, so I will add the options as mentioned below.

[Sebastian Roth]

@george1421 @Quazz I just added the two kernel options as mentioned below to the x64 kernel config (not pushed the change yet).

While CONFIG_INTEL_IDLE is available in x86 (32 bit) config as well CONFIG_MAXSMP is not (depends on X86_64 [=y]). Should I leave CONFIG_NR_CPUS set to 8 (default I think) or increase it to 16, 32, 64?

For ARM kernel config we don’t have CONFIG_INTEL_IDLE nor CONFIG_MAXSMP but can adjust CONFIG_NR_CPUS too. 16, 32, 64?

[Quazz]

@Sebastian-Roth I think it’s fine to leave X86 to 8 since I don’t think they make huge multicore 32 bit CPUs. (wouldn’t really make sense to me anyway) Though I also think it wouldn’t necessarily hurt to change it, why bother if it’s not needed? I also believe 8 is default for X86 anyway

As for ARM: https://www.phoronix.com/scan.php?page=news_item&px=ARM64-256-Default-NR_CPUS

Default in Linux 5.1 ARM 64 is 256 now. (current default being 64)

[Sebastian Roth]

@Quazz Thanks, done: https://github.com/FOGProject/fos/issues/31