> -----Original Message----- > From: owner-linux-mm@xxxxxxxxx [mailto:owner-linux-mm@xxxxxxxxx] On > Behalf Of Oscar Salvador > Sent: Tuesday, November 24, 2020 11:25 PM > To: Muchun Song <songmuchun@xxxxxxxxxxxxx> > Cc: corbet@xxxxxxx; mike.kravetz@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; > mingo@xxxxxxxxxx; bp@xxxxxxxxx; x86@xxxxxxxxxx; hpa@xxxxxxxxx; > dave.hansen@xxxxxxxxxxxxxxx; luto@xxxxxxxxxx; peterz@xxxxxxxxxxxxx; > viro@xxxxxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; paulmck@xxxxxxxxxx; > mchehab+huawei@xxxxxxxxxx; pawan.kumar.gupta@xxxxxxxxxxxxxxx; > rdunlap@xxxxxxxxxxxxx; oneukum@xxxxxxxx; anshuman.khandual@xxxxxxx; > jroedel@xxxxxxx; almasrymina@xxxxxxxxxx; rientjes@xxxxxxxxxx; > willy@xxxxxxxxxxxxx; mhocko@xxxxxxxx; Song Bao Hua (Barry Song) > <song.bao.hua@xxxxxxxxxxxxx>; duanxiongchun@xxxxxxxxxxxxx; > linux-doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; > linux-fsdevel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v6 07/16] x86/mm/64: Disable PMD page mapping of > vmemmap > > On Tue, Nov 24, 2020 at 05:52:50PM +0800, Muchun Song wrote: > > If we enable the CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, we can just > > disbale PMD page mapping of vmemmap to simplify the code. In this > > case, we do not need complex code doing vmemmap page table > > manipulation. This is a way to simply the first version of this > > patch series. In the future, we can add some code doing page table > > manipulation. > > IIRC, CONFIG_HUGETLB_PAGE_FREE_VMEMMAP was supposed to be enabled > by default, > right? > And we would control whether we __really__ want to this by a boot option, > which was disabled by default? > > If you go for populating the memmap with basepages by checking > CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, would not everybody, even the > ones that > did not enable this by the boot option be affected? > I would believe we could only bypass the pmd mapping of vmemmap while free_vmemmap is explicitly enabled. pmd mapping shouldn't be disabled in default. Would a cmdline of enabling vmemmap_free be used for the first patchset? > -- > Oscar Salvador > SUSE L3 Thanks Barry
