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Mon, 25 Jan 2021 04:32:08 -0800 (PST) MIME-Version: 1.0 References: <20210117151053.24600-1-songmuchun@bytedance.com> <20210117151053.24600-10-songmuchun@bytedance.com> <7550ebba-fdb5-0dc9-a517-dda56bd105d9@redhat.com> <20210125120827.GA29289@linux> In-Reply-To: <20210125120827.GA29289@linux> From: Muchun Song Date: Mon, 25 Jan 2021 20:31:31 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v13 09/12] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap To: Oscar Salvador Cc: David Hildenbrand , Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Michal Hocko , "Song Bao Hua (Barry Song)" , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jan 25, 2021 at 8:08 PM Oscar Salvador wrote: > > On Mon, Jan 25, 2021 at 12:43:23PM +0100, David Hildenbrand wrote: > > > - if (end - start < PAGES_PER_SECTION * sizeof(struct page)) > > > + if (is_hugetlb_free_vmemmap_enabled() || > > > + end - start < PAGES_PER_SECTION * sizeof(struct page)) > > > > This looks irresponsible. You ignore any altmap, even though current > > altmap users (ZONE_DEVICE) will not actually result in applicable > > vmemmaps that huge pages could ever use. > > > > Why do you ignore the altmap completely? This has to be properly > > documented, but IMHO it's not even the right approach to mess with > > altmap here. > > The goal was not to ignore altmap but to disable PMD mapping sections > when the feature was enabled. > Shame on me I did not notice that with this, altmap will be ignored. > > Something like below maybe: Yeah, Thanks a lot. > > int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, > struct vmem_altmap *altmap) > { > int err; > bool populate_base_pages = false; > > if ((end - start < PAGES_PER_SECTION * sizeof(struct page)) || > (is_hugetlb_free_vmemmap_enabled() && !altmap)) > populate_base_pages = true; > > if (populate_base_pages) { > err = vmemmap_populate_basepages(start, end, node, NULL); > } else if (boot_cpu_has(X86_FEATURE_PSE)) { > .... > > > > > > -- > > Thanks, > > > > David / dhildenb > > > > > > -- > Oscar Salvador > SUSE L3