On Wed, Aug 28, 2019 at 06:02:24PM +0200, Michal Hocko wrote: > > > > > > Any idea about a bad case? > > > > Not really. > > > > How bad you want it to get? How many processes share the page? Access > > pattern? Locking situation? > > Let's say how hard a regular user can make this? It bumped to ~170 ms if each THP was mapped 5 times. Adding ptl contention (tight loop of MADV_DONTNEED) in 3 processes that maps the page, the time to split bumped to ~740ms. Overally, it's reasonable to take ~100ms per GB of huge pages as rule of thumb. -- Kirill A. Shutemov
