On Tue, Sep 08, 2020 at 03:48:08PM +0530, Anshuman Khandual wrote: > On 09/03/2020 10:26 PM, Catalin Marinas wrote: > > On Mon, Aug 17, 2020 at 02:49:43PM +0530, Anshuman Khandual wrote: > >> pmd_present() and pmd_trans_huge() are expected to behave in the following > >> manner during various phases of a given PMD. It is derived from a previous > >> detailed discussion on this topic [1] and present THP documentation [2]. > >> > >> pmd_present(pmd): > >> > >> - Returns true if pmd refers to system RAM with a valid pmd_page(pmd) > >> - Returns false if pmd does not refer to system RAM - Invalid pmd_page(pmd) > > > > The second bullet doesn't make much sense. If you have a pmd mapping of > > some I/O memory, pmd_present() still returns true (as does > > pte_present()). > > Derived this from an earlier discussion (https://lkml.org/lkml/2018/10/17/231) > but current representation here might not be accurate. > > Would this be any better ? > > pmd_present(pmd): > > - Returns true if pmd refers to system RAM with a valid pmd_page(pmd) > - Returns false if pmd refers to a migration or swap entry Yes, that's better -- Catalin
