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[209.85.220.65]) by mx.google.com with SMTPS id g3sor115595eje.40.2019.05.04.08.56.01 for (Google Transport Security); Sat, 04 May 2019 08:56:02 -0700 (PDT) Received-SPF: pass (google.com: domain of pasha.tatashin@soleen.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@soleen.com header.s=google header.b=ZrdWTpIg; spf=pass (google.com: domain of pasha.tatashin@soleen.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=D/xUA4we+CfWIBMstY2ZZGUlR8dNMfA/8aG9kri4RSo=; b=ZrdWTpIgvvrF424jIp+wrwRFjns9Vws1VhvhVyeQLQ8yUB0K/RtorMBF6hIJ8qdZr/ EMNY9XodjCnuUSks5vvIic5f25dogm0UqOVLHW1qPGEa5AIPjIUxhdJ6vyyG+zQwjSVb Es6EOhcjogmP+jv9TmQXzop3fT6A5kIYR4QdSUVCyYBPBKteqVQv+Mr+7uyZmdwuPuLX 0XuWwnIzEw5utfKyj4eEzEOCUe+bSQvYbR0zp66AsLiLTgD/1mSrqF+0Fi72jzDJxuSU jUBy/A5BIp4B5w1mm3m2TYLN7uiDehFBdz/RSQ6Qku4HP2JVpf746kbtSaqqIkqt/mKN QUJA== X-Google-Smtp-Source: APXvYqwL1+OT6I7xDELCdfNz+oPiiC/N2OEv5oobeObUVGp+lISzqLMPEiMy5oB5eqPGvxPFUEwyNJ8Pi/qnMyQIUAw= X-Received: by 2002:a17:906:3fca:: with SMTP id k10mr11517604ejj.126.1556985361722; Sat, 04 May 2019 08:56:01 -0700 (PDT) MIME-Version: 1.0 References: <155552633539.2015392.2477781120122237934.stgit@dwillia2-desk3.amr.corp.intel.com> <155552634075.2015392.3371070426600230054.stgit@dwillia2-desk3.amr.corp.intel.com> <20190501232517.crbmgcuk7u4gvujr@soleen.tm1wkky2jk1uhgkn0ivaxijq1c.bx.internal.cloudapp.net> In-Reply-To: From: Pavel Tatashin Date: Sat, 4 May 2019 11:55:50 -0400 Message-ID: Subject: Re: [PATCH v6 01/12] mm/sparsemem: Introduce struct mem_section_usage To: Dan Williams Cc: Andrew Morton , Michal Hocko , Vlastimil Babka , Logan Gunthorpe , Linux MM , linux-nvdimm , Linux Kernel Mailing List , David Hildenbrand 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: > > I'm ok with it being 16M for now unless it causes a problem in > > practice, i.e. something like the minimum hardware mapping alignment > > for physical memory being less than 16M. > > On second thought, arbitrary differences across architectures is a bit > sad. The most common nvdimm namespace alignment granularity is > PMD_SIZE, so perhaps the default sub-section size should try to match > that default. I think that even if you keep it 16M for now, at very least you should make the map_active bitmap scalable so it will be possible to change as required later without revisiting all functions that use it. Making it a static array won't slowdown x86, as it will be still a single 64-bit word on x86. Pasha