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[209.132.183.28]) by mx.google.com with ESMTPS id g9si961708uac.187.2019.07.11.08.25.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Jul 2019 08:25:56 -0700 (PDT) Received-SPF: pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=nitesh@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 82F77285AE; Thu, 11 Jul 2019 15:25:55 +0000 (UTC) Received: from [10.18.17.163] (dhcp-17-163.bos.redhat.com [10.18.17.163]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A8CB860C05; Thu, 11 Jul 2019 15:25:48 +0000 (UTC) Subject: Re: [RFC][Patch v11 1/2] mm: page_hinting: core infrastructure To: Dave Hansen , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, yang.zhang.wz@gmail.com, riel@surriel.com, david@redhat.com, mst@redhat.com, dodgen@google.com, konrad.wilk@oracle.com, dhildenb@redhat.com, aarcange@redhat.com, alexander.duyck@gmail.com, john.starks@microsoft.com, mhocko@suse.com References: <20190710195158.19640-1-nitesh@redhat.com> <20190710195158.19640-2-nitesh@redhat.com> <3f9a7e7b-c026-3530-e985-804fc7f1ec31@intel.com> From: Nitesh Narayan Lal Openpgp: preference=signencrypt Autocrypt: addr=nitesh@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <3f9a7e7b-c026-3530-e985-804fc7f1ec31@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 11 Jul 2019 15:25:55 +0000 (UTC) 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 7/10/19 4:45 PM, Dave Hansen wrote: > On 7/10/19 12:51 PM, Nitesh Narayan Lal wrote: >> +struct zone_free_area { >> + unsigned long *bitmap; >> + unsigned long base_pfn; >> + unsigned long end_pfn; >> + atomic_t free_pages; >> + unsigned long nbits; >> +} free_area[MAX_NR_ZONES]; > Why do we need an extra data structure. What's wrong with putting > per-zone data in ... 'struct zone'? Will it be acceptable to add fields in struct zone, when they will only be used by page hinting? > The cover letter claims that it > doesn't touch core-mm infrastructure, but if it depends on mechanisms > like this, I think that's a very bad thing. > > To be honest, I'm not sure this series is worth reviewing at this point= =2E > It's horribly lightly commented and full of kernel antipatterns lik > > void func() > { > if () { > ... indent entire logic > ... of function > } > } I usually run checkpatch to detect such indentation issues. For the patches, I shared it didn't show me any issues. > > It has big "TODO"s. It's virtually comment-free. I'm shocked it's at > the 11th version and still looking like this. > >> + >> + for (zone_idx =3D 0; zone_idx < MAX_NR_ZONES; zone_idx++) { >> + unsigned long pages =3D free_area[zone_idx].end_pfn - >> + free_area[zone_idx].base_pfn; >> + bitmap_size =3D (pages >> PAGE_HINTING_MIN_ORDER) + 1; >> + if (!bitmap_size) >> + continue; >> + free_area[zone_idx].bitmap =3D bitmap_zalloc(bitmap_size, >> + GFP_KERNEL); > This doesn't support sparse zones. We can have zones with massive > spanned page sizes, but very few present pages. On those zones, this > will exhaust memory for no good reason. > > Comparing this to Alex's patch set, it's of much lower quality and at a= > much earlier stage of development. The two sets are not really even > comparable right now. This certainly doesn't sell me on (or even reall= y > enumerate the deltas in) this approach vs. Alex's. > --=20 Thanks Nitesh