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[121.45.173.48]) by smtp.gmail.com with ESMTPSA id a3sm433368pfi.206.2021.03.03.21.06.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Mar 2021 21:06:22 -0800 (PST) Date: Thu, 4 Mar 2021 16:06:19 +1100 From: Balbir Singh To: Muchun Song Cc: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, willy@infradead.org, osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com, david@redhat.com, naoya.horiguchi@nec.com, joao.m.martins@oracle.com, duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Miaohe Lin Subject: Re: [PATCH v17 2/9] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Message-ID: <20210304050619.GC1223287@balbir-desktop> References: <20210225132130.26451-1-songmuchun@bytedance.com> <20210225132130.26451-3-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210225132130.26451-3-songmuchun@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Feb 25, 2021 at 09:21:23PM +0800, Muchun Song wrote: > The option HUGETLB_PAGE_FREE_VMEMMAP allows for the freeing of > some vmemmap pages associated with pre-allocated HugeTLB pages. > For example, on X86_64 6 vmemmap pages of size 4KB each can be > saved for each 2MB HugeTLB page. 4094 vmemmap pages of size 4KB > each can be saved for each 1GB HugeTLB page. > > When a HugeTLB page is allocated or freed, the vmemmap array > representing the range associated with the page will need to be > remapped. When a page is allocated, vmemmap pages are freed > after remapping. When a page is freed, previously discarded > vmemmap pages must be allocated before remapping. > > The config option is introduced early so that supporting code > can be written to depend on the option. The initial version of > the code only provides support for x86-64. > > Like other code which frees vmemmap, this config option depends on > HAVE_BOOTMEM_INFO_NODE. The routine register_page_bootmem_info() is > used to register bootmem info. Therefore, make sure > register_page_bootmem_info is enabled if HUGETLB_PAGE_FREE_VMEMMAP > is defined. > > Signed-off-by: Muchun Song > Reviewed-by: Oscar Salvador > Acked-by: Mike Kravetz > Reviewed-by: Miaohe Lin > --- Reviewed-by: Balbir Singh