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Wed, 16 Dec 2020 06:26:42 -0800 (PST) MIME-Version: 1.0 References: <20201213154534.54826-1-songmuchun@bytedance.com> <20201213154534.54826-11-songmuchun@bytedance.com> <20201216140340.GE29394@linux> In-Reply-To: <20201216140340.GE29394@linux> From: Muchun Song Date: Wed, 16 Dec 2020 22:26:02 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v9 10/11] mm/hugetlb: Gather discrete indexes of tail page To: Oscar Salvador Cc: 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)" , David Hildenbrand , 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 Wed, Dec 16, 2020 at 10:03 PM Oscar Salvador wrote: > > On Sun, Dec 13, 2020 at 11:45:33PM +0800, Muchun Song wrote: > > For HugeTLB page, there are more metadata to save in the struct page. > > But the head struct page cannot meet our needs, so we have to abuse > > other tail struct page to store the metadata. In order to avoid > > conflicts caused by subsequent use of more tail struct pages, we can > > gather these discrete indexes of tail struct page. In this case, it > > will be easier to add a new tail page index later. > > > > There are only (RESERVE_VMEMMAP_SIZE / sizeof(struct page)) struct > > page structs can be used when CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, so > "that can be..." Thanks. > > > add a BUILD_BUG_ON to catch invalid usage of the tail struct page. > > > > Signed-off-by: Muchun Song > > I think this makes the current situation with metadata usage in sub-pages > easier to track. Agree. > > Reviewed-by: Oscar Salvador Thank you. > > -- > Oscar Salvador > SUSE L3 -- Yours, Muchun