> On Nov 28, 2020, at 4:45 PM, Nadav Amit <nadav.amit@xxxxxxxxx> wrote: > > From: Nadav Amit <namit@xxxxxxxxxx> > > Userfaultfd writes can now be used for copy/zeroing. When using iouring > with userfaultfd, performing the copying/zeroing on the faulting thread > instead of the handler/iouring thread has several advantages: > > (1) The data of the faulting thread will be available on the local > caches, which would make subsequent memory accesses faster. > > (2) find_vma() would be able to use the vma-cache, which cannot be done > from a different process or io-uring kernel thread. > > (3) The page is more likely to be allocated on the correct NUMA node. > > To do so, userfaultfd work queue structs are extended to hold the > information that is required for the faulting thread to copy/zero. The > handler wakes one of the faulting threads to perform the copy/zero and > that thread wakes the other threads after the zero/copy is done. I noticed some bugs of mine in this patch, but more importantly I realized that the there may be a more performant solution to do the copying on the faulting thread - without async-writes. Please do not review this patch and the next one (12/13). Feedback for the rest of the series is of course welcomed. Regards, Nadav
