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b=hWvGvwGSg6cFQfnz1kfeWqSIvi9bUfwv83y1MDgHl3kxtcPgXjljetTL0pOcvef++ /52FoN1OVfb4z9I/p8voZFnyvw894wJMt7D7gHbtFuz7mRSh8JoG7jY7vf9hPqeNln QiNGpAQhbLbG6+tsGZ9EB5WioLiYQPitG+ooJuCbiC/g2tVM3cO9xr91RQUxb4kvWn IuZeBEgZc+FLB7A2oXurUFqw86ZEw6OVxKATZeyv59gFiRZG+7aS2aM5VTxNe1B9u/ E3P1jLmOBniVQi2N28k1gMl/dNOYSWbT9KzjHB8GKM79HMCK3ndSZe3MFSoMOskbh/ 2UaZRY7n+lLPA== Date: Sun, 12 May 2024 07:45:15 -0600 From: Mike Rapoport To: Oscar Salvador Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org Subject: Re: [LSF/MM/BFP TOPIC] Deprecate SPARSEMEM and have only SPARSEMEM_VMEMMAP Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6013140015 X-Stat-Signature: iczo554jbkifyry5ypebqj5oithwyih6 X-HE-Tag: 1715521614-386883 X-HE-Meta: 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 Eq2RReZc wbi08HPtIUgQjWiXdmJWv0j1+lVdtz4S+p7O3JomTmAmsJVNf6YK4JenBOdvVm2jvFVNtmhu99KkbYOkvRoj2mGAOmCSVH3lSGCunQhU38dK0Md4MKtSlriUcm2HfP0qagwzT06Z10L3yV/BRFElJ9J9MOLa85wzdZ83UeGqWJFPCQdz2aVpIvmrzBWRmiAu06W5r+rvfHPEQ5/FlXwk+gsCur6DbSgJ2QGuMjXo1q0vyXME= 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: List-Subscribe: List-Unsubscribe: On Fri, May 10, 2024 at 11:03:14AM +0200, Oscar Salvador wrote: > Hi all, > > I would like to discuss the following topic in the LSFMM. > > We have SPARSEMEM memory model and SPARSEMEM_VMEMMAP, where the only difference > between the two of them is that the latter allocates a virtual chunk to represent > the memmap array, which speeds operations like > page_to_pfn/pfn_to_page/nth_page/folio_page_idx. ... > I did some research on which arches use CONFIG_SPARSE_MEMMAP/VMEMMAP or > none(using flatmem?). FLATMEM it is. > SPARSE_MEMMAP SPARSE_VMEMMAP > arc > arm X > arm64 X X > csky > hexagon > loongarch X X > m68k > microblaze > mips X > nios2 > openrisc > parisc > powerpc X X > riscv X X > s390 X X > sh X > sparc X X > um > x86 X X > xtensa > > arm, mips, parisc and sh operate with SPARSE_MEMMAP but are lacking code for > SPARSE_VMEMMAP. arm can use "sparse flatmem" in the sense that it can free unused parts of the memory map so FLATMEM does not have memory overhead with sparsely located memory banks. So possible we can just drop SPARSEMEM on arm. But I agree with Matthew that for this discussion we'd need arch maintainers to participate. > Thanks > > -- > Oscar Salvador > SUSE Labs > -- Sincerely yours, Mike.