On 12/18/18 1:38 PM, Andi Kleen wrote: >> I misunderstood, you mean 32bit kernel, not 32bit machine. Theoretically >> 32bit >> kernel can use AVX512, but not sure if anyone use it like this. >> get_jiffies_64() >> includes jiffies_lock ops so not good in context switch. So I want to use raw >> jiffies_64 here. jiffies is a good candidate but it has wraparound overflow >> issue. >> Other time source are expensive here. >> >> Should I limit the code only running on 64bit kernel? > Yes making it 64bit only should be fine.
I think I'd rather just disable AVX512 itself on 32-bit and be done with it. I think more than half of the ~2k of XSAVE space that it consumes in *every* *task* is just pure waste because it has to be 0's. This ~2k of extra space is also lowmem, which makes it even more valuable.
