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[2003:cb:c727:9100:ccc4:124c:ad98:2c81]) by smtp.gmail.com with ESMTPSA id f23sm1340793ejj.128.2022.01.09.04.25.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 09 Jan 2022 04:25:46 -0800 (PST) Message-ID: <4821e34b-b7b5-a281-588d-fe8242856b6b@redhat.com> Date: Sun, 9 Jan 2022 13:25:46 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 To: "Ranjan, Vikash" , "linux-mm@kvack.org" References: <14101f99fda548dc960e2041a6807536@HIBDWSMB03.ad.harman.com> From: David Hildenbrand Organization: Red Hat Subject: Re: memory_block_size reduction in memory hot plug, can we reduced it to 1GB,currently it is 4GB In-Reply-To: <14101f99fda548dc960e2041a6807536@HIBDWSMB03.ad.harman.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 77D81A0006 X-Stat-Signature: 8ijc44c9uqbgydeug6km66x64ht93isy Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=EJJqT18P; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf25.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=david@redhat.com X-HE-Tag: 1641731150-226686 Content-Transfer-Encoding: quoted-printable 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: Hi >=20 > We are trying to enable memory hot plug for our device's based on arm64= , > is it possible to reduce memory_block_size to 1 GB or lesser as > currently it is 4GB. ... are you sure it's 4GB? I never heard that magic number on arm64 before. The section size is 512 MiB on arm64 with 64k and 128 MiB with 4k= . >=20 > If you have any info on updated patch or any other way we can do this, > please let us know. >=20 > =C2=A0After applying attached test patch (for reduction of memory_block= _size > to 1 GB),we are getting below error. Probe is working fine in case of 4= GB. >=20 I think I am missing something important. #define MIN_MEMORY_BLOCK_SIZE (1UL << SECTION_SIZE_BITS) arch/arm64/include/asm/sparsemem.h:#define SECTION_SIZE_BITS 29 arch/arm64/include/asm/sparsemem.h:#define SECTION_SIZE_BITS 27 -> 512 MiB / 128 MiB arm64 does not override memory_block_size_bytes(), so it matches exactly these numbers. --=20 Thanks, David / dhildenb