On 08/24/2015 12:17 PM, Konstantin Khlebnikov wrote: >> >> I am in the middle of implementing lock on fault this way, but I cannot >> see how we will hanlde mremap of a lock on fault region. Say we have >> the following: >> >> addr = mmap(len, MAP_ANONYMOUS, ...); >> mlock(addr, len, MLOCK_ONFAULT); >> ... >> mremap(addr, len, 2 * len, ...) >> >> There is no way for mremap to know that the area being remapped was lock >> on fault so it will be locked and prefaulted by remap. How can we avoid >> this without tracking per vma if it was locked with lock or lock on >> fault? > > remap can count filled ptes and prefault only completely populated areas.
Does (and should) mremap really prefault non-present pages? Shouldn't it just prepare the page tables and that's it? > There might be a problem after failed populate: remap will handle them > as lock on fault. In this case we can fill ptes with swap-like non-present > entries to remember that fact and count them as should-be-locked pages. I don't think we should strive to have mremap try to fix the inherent unreliability of mmap (MAP_POPULATE)?
