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" ...
