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"
