On 1/29/19 3:40 PM, Andrea Arcangeli wrote: > In addition to the above "NUMA remote THP vs NUMA local non-THP > tradeoff" topic, there are other developments in "userfaultfd" land that > are approaching merge readiness and that would be possible to provide a > short overview about: > > - Peter Xu made significant progress in finalizing the userfaultfd-WP > support over the last few months. That feature was planned from the > start and it will allow userland to do some new things that weren't > possible to achieve before. In addition to synchronously blocking > write faults to be resolved by an userland manager, it has also the > ability to obsolete the softdirty feature, because it can provide > the same information, but with O(1) complexity (as opposed of the > current softdirty O(N) complexity) similarly to what the Page > Modification Logging (PML) does in hardware for EPT write accesses. I would be interested in this topic as well. IIRC, Peter's patches do not address hugetlbfs support. I put together patches for this some time back. At the time, they worked as well as userfaultfd-WP support for normal base pages: not too well :). Once base page support is finalized, I suspect I will be involved in hugetlbfs support. -- Mike Kravetz
