On Thu, Jan 7, 2021 at 7:16 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > On Thu 07-01-21 10:52:21, Muchun Song wrote: > > On Thu, Jan 7, 2021 at 12:13 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > On Wed 06-01-21 16:47:34, Muchun Song wrote: > > > > If the refcount is one when it is migrated, it means that the page > > > > was freed from under us. So we are done and do not need to migrate. > > > > > > Is this common enough that it would warrant the explicit check for each > > > migration? > > > > Are you worried about the overhead caused by the check? Thanks. > > I am not as worried as I would like to see some actual justification for > this optimization. OK. The HugeTLB page can be freed after it was isolated but before being migrated. Right? If we catch this case, it is an optimization. I do this just like unmap_and_move() does for a base page. > -- > Michal Hocko > SUSE Labs
