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[209.85.220.65]) by mx.google.com with SMTPS id z16sor1711854oth.36.2019.03.20.08.34.32 for (Google Transport Security); Wed, 20 Mar 2019 08:34:32 -0700 (PDT) Received-SPF: pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@intel-com.20150623.gappssmtp.com header.s=20150623 header.b=S1BTeZ60; spf=pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=uNIyVUbxeFEDoIbxgtBJkCNkY0r/4CBODhtc3HnZvfo=; b=S1BTeZ60qB8Kcw6wQHVvBU2Cw4rNly7jAnT1sv/cmmSV2k4deA9yMb7w1j6/m2Q7eN I0qQK4ihRRtoLqjMr9JBlDJxL03hrUvIAZ4zrfaYSZwb9Rz9vc0AqJaovdTBauLDCGg2 5ak3wWitVxY9gkpb4x+iB0EYEiq5A8H80kh1YPOC6PxGa9koz5UavcxbNY+BLgYvx3Dh J6CAW3BvJDoHbLCvHJV56Y1nul+KP6YMIlIA2Wo3Ei5mh1A0af24SEv5q1xMa9+k6XxD mjNrgoBWeZEj3sPoSMDW+6K9ngq6F4U19oVo6Hc1SCLZkYrHIijoo2AnD4h8DCLqdEFt xSiw== X-Google-Smtp-Source: APXvYqxh599eRoi9kopKodFa8svBbY69SGQsc6Ak3KgIjjSVU6tD1uVGa0VbJ5R8O2CduKZXexy6I0CD6Z58iDK2Ytg= X-Received: by 2002:a9d:224a:: with SMTP id o68mr6279518ota.214.1553096071716; Wed, 20 Mar 2019 08:34:31 -0700 (PDT) MIME-Version: 1.0 References: <20190228083522.8189-1-aneesh.kumar@linux.ibm.com> <20190228083522.8189-2-aneesh.kumar@linux.ibm.com> <87k1hc8iqa.fsf@linux.ibm.com> <871s3aqfup.fsf@linux.ibm.com> <87bm267ywc.fsf@linux.ibm.com> <878sxa7ys5.fsf@linux.ibm.com> In-Reply-To: <878sxa7ys5.fsf@linux.ibm.com> From: Dan Williams Date: Wed, 20 Mar 2019 08:34:20 -0700 Message-ID: Subject: Re: [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default To: "Aneesh Kumar K.V" Cc: Jan Kara , linux-nvdimm , Michael Ellerman , Linux Kernel Mailing List , Linux MM , Ross Zwisler , Andrew Morton , linuxppc-dev , "Kirill A . Shutemov" 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, Mar 20, 2019 at 1:09 AM Aneesh Kumar K.V wrote: > > Aneesh Kumar K.V writes: > > > Dan Williams writes: > > > >> > >>> Now what will be page size used for mapping vmemmap? > >> > >> That's up to the architecture's vmemmap_populate() implementation. > >> > >>> Architectures > >>> possibly will use PMD_SIZE mapping if supported for vmemmap. Now a > >>> device-dax with struct page in the device will have pfn reserve area aligned > >>> to PAGE_SIZE with the above example? We can't map that using > >>> PMD_SIZE page size? > >> > >> IIUC, that's a different alignment. Currently that's handled by > >> padding the reservation area up to a section (128MB on x86) boundary, > >> but I'm working on patches to allow sub-section sized ranges to be > >> mapped. > > > > I am missing something w.r.t code. The below code align that using nd_pfn->align > > > > if (nd_pfn->mode == PFN_MODE_PMEM) { > > unsigned long memmap_size; > > > > /* > > * vmemmap_populate_hugepages() allocates the memmap array in > > * HPAGE_SIZE chunks. > > */ > > memmap_size = ALIGN(64 * npfns, HPAGE_SIZE); > > offset = ALIGN(start + SZ_8K + memmap_size + dax_label_reserve, > > nd_pfn->align) - start; > > } > > > > IIUC that is finding the offset where to put vmemmap start. And that has > > to be aligned to the page size with which we may end up mapping vmemmap > > area right? Right, that's the physical offset of where the vmemmap ends, and the memory to be mapped begins. > > Yes we find the npfns by aligning up using PAGES_PER_SECTION. But that > > is to compute howmany pfns we should map for this pfn dev right? > > > > Also i guess those 4K assumptions there is wrong? Yes, I think to support non-4K-PAGE_SIZE systems the 'pfn' metadata needs to be revved and the PAGE_SIZE needs to be recorded in the info-block.