From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C01FC74A52 for ; Thu, 11 Jul 2019 11:48:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F8532166E for ; Thu, 11 Jul 2019 11:48:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728240AbfGKLsm convert rfc822-to-8bit (ORCPT ); Thu, 11 Jul 2019 07:48:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53798 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727956AbfGKLsm (ORCPT ); Thu, 11 Jul 2019 07:48:42 -0400 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 6C880308218D; Thu, 11 Jul 2019 11:48:41 +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 81F6B19C70; Thu, 11 Jul 2019 11:48:32 +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: 8BIT 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 [10.5.110.47]); Thu, 11 Jul 2019 11:48:41 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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'? 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 > } > } > > It has big "TODO"s. It's virtually comment-free. I'm shocked it's at > the 11th version and still looking like this. One of the reasons for being on v11 was that the entire design has changed a few times. But that's no excuse, I understand what you are saying and I will work on it and improve 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. Thanks, I will look into this. > > 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