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[209.132.183.28]) by mx.google.com with ESMTPS id r5si1891983vsr.127.2019.07.11.08.50.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Jul 2019 08:50:23 -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-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C3BB5309265A; Thu, 11 Jul 2019 15:50:22 +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 66F7F19C69; Thu, 11 Jul 2019 15:50:08 +0000 (UTC) Subject: Re: [RFC][Patch v11 1/2] mm: page_hinting: core infrastructure From: Nitesh Narayan Lal 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> <0b871cf1-e54f-f072-1eaf-511a03c2907f@redhat.com> 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: <0b871cf1-e54f-f072-1eaf-511a03c2907f@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 11 Jul 2019 15:50:23 +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 7/11/19 11:25 AM, Nitesh Narayan Lal wrote: > 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. >> 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. My bad I think I jumped here, I saw what you are referring to here. I will fix these kind of things. >> 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 = 0; zone_idx < MAX_NR_ZONES; zone_idx++) { >>> + unsigned long pages = free_area[zone_idx].end_pfn - >>> + free_area[zone_idx].base_pfn; >>> + bitmap_size = (pages >> PAGE_HINTING_MIN_ORDER) + 1; >>> + if (!bitmap_size) >>> + continue; >>> + free_area[zone_idx].bitmap = 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 really >> enumerate the deltas in) this approach vs. Alex's. >> -- Thanks Nitesh