On Wed, Jun 26, 2024 at 11:18 PM Ryan Roberts <ryan.roberts@xxxxxxx> wrote: > > On 26/06/2024 16:15, Matthew Wilcox wrote: > > On Wed, Jun 26, 2024 at 12:07:04PM +0100, Ryan Roberts wrote: > >> On 26/06/2024 04:06, Zi Yan wrote: > >>> On Tue Jun 25, 2024 at 10:49 PM EDT, ran xiaokai wrote: > >>>> From: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx> > >>>> > >>>> KPF_COMPOUND_HEAD and KPF_COMPOUND_TAIL are set on "common" compound > >>>> pages, which means of any order, but KPF_THP should only be set > >>>> when the folio is a 2M pmd mappable THP. > >> > >> Why should KPF_THP only be set on 2M THP? What problem does it cause as it is > >> currently configured? > >> > >> I would argue that mTHP is still THP so should still have the flag. And since > >> these smaller mTHP sizes are disabled by default, only mTHP-aware user space > >> will be enabling them, so I'll naively state that it should not cause compat > >> issues as is. > >> > >> Also, the script at tools/mm/thpmaps relies on KPF_THP being set for all mTHP > >> sizes to function correctly. So that would need to be reworked if making this > >> change. > > > > I told you you'd run into trouble calling them "mTHP" ... > > "There are two hard things in computer science; naming, cache invalidation and > off-by-one errors" Totally agree. Naming things can be surprisingly challenging ;) Thanks, Lance >
