Hey Michal, Thanks for taking time to review! On some servers within our company, we deploy a daemon responsible for monitoring and updating local applications. Some applications prefer not to use THP, so the daemon calls prctl to disable THP before fork/exec. Conversely, for other applications, the daemon calls prctl to enable THP before fork/exec. Ideally, the daemon should invoke prctl after the fork, but its current implementation follows the described approach. BR, Lance On Tue, Jan 30, 2024 at 12:28 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > On Mon 29-01-24 13:45:51, Lance Yang wrote: > > khugepaged scans the entire address space in the > > background for each given mm, looking for > > opportunities to merge sequences of basic pages > > into huge pages. However, when an mm is inserted > > to the mm_slots list, and the MMF_DISABLE_THP flag > > is set later, this scanning process becomes > > unnecessary for that mm and can be skipped to avoid > > redundant operations, especially in scenarios with > > a large address space. > > Is this a real problem? I thought that the prctl is called > on the parent before fork/exec. Or are you aware of any > applications which do call prctl late enough that the race > would be actually observable? > -- > Michal Hocko > SUSE Labs
