On Sun, Sep 12, 2021, at 18:30, Alexey Dobriyan wrote: > How about making everything "unsigned long" or even "u64" like NIC > drivers do? I see some possible hurdles ahead: - Not all architectures have atomic operations for 64-bit values All those "unsigned int" counters are incremented with __this_cpu_inc() which tries to use atomics if possible. Though, I'm not quite sure how this works for read side which does not seem to use atomic reads at all. I guess, just by the virtue of properly aligned 32-bit reads being atomic everywhere? If that's so, I think widening counters to 64 bits will come with an asterisk. - We'll need to update all counters to be 64-bit. Like, *everyone*. Every field that gets summed up needs to be 64-bit (or else wrap-arounds will be incorrect). Basically every counter in every irq_cpustat_t will need to become twice as wide. If that's a fine price to pay for accurate, full-width counters... Previously I thought that some of these counters even come from hardware, but now that I'm reviewing them, that does not seem to be the case. Thankfully. So right now I don't see why it shouldn't be doable in theory. I'll give it a shot, I guess, and see how it works in practice, at least as far as the patches go (since I can't really test on all architectures).
