On Thu, May 02, 2024 at 11:11:04AM +0200, Thomas Hellström wrote: > It's true the cpu vma lookup is a remnant from amdkfd. The idea here is > to replace that with fixed prefaulting ranges of tunable size. So far, > as you mention, the prefaulting range has been determined by the CPU > vma size. Given previous feedback, this is going to change. Perhaps limiting prefault to a VMA barrier is a reasonable thing to do, but the implementation should be pushed into hmm_range_fault and not open coded in the driver. > Still the prefaulting range needs to be restricted to avoid -EFAULT > failures in hmm_range_fault(). That can ofc be done by calling it > without HMM_PFN_REQ_FAULT for the range and interpret the returned > pnfs. Yes, this is exactly what that feature is for, you mark your prefetch differently from the fault critical page(s). > There is a performance concern of this approach as compared to > peeking at the CPU vmas directly, since hmm_range_fault() would need to > be called twice. Any guidelines ideas here? If there is something wrong with hmm_range_fault() then please fix it. I'm not sure why you'd call it twice, the HMM_PFN_REQ_FAULT is per PFN? Jason
