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 4C85DC76195 for ; Mon, 15 Jul 2019 14:42:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 26040217F9 for ; Mon, 15 Jul 2019 14:42:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731717AbfGOOmH (ORCPT ); Mon, 15 Jul 2019 10:42:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41278 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404541AbfGOOkq (ORCPT ); Mon, 15 Jul 2019 10:40:46 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 92433309175E; Mon, 15 Jul 2019 14:40:45 +0000 (UTC) Received: from [10.36.118.52] (unknown [10.36.118.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 781AD5D9C8; Mon, 15 Jul 2019 14:40:31 +0000 (UTC) Subject: Re: [RFC][Patch v11 1/2] mm: page_hinting: core infrastructure From: David Hildenbrand To: Dave Hansen , Nitesh Narayan Lal , 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, 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> <46336efb-3243-0083-1d20-7e8578131679@redhat.com> Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwX4EEwECACgFAljj9eoCGwMFCQlmAYAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEE3eEPcA/4Na5IIP/3T/FIQMxIfNzZshIq687qgG 8UbspuE/YSUDdv7r5szYTK6KPTlqN8NAcSfheywbuYD9A4ZeSBWD3/NAVUdrCaRP2IvFyELj xoMvfJccbq45BxzgEspg/bVahNbyuBpLBVjVWwRtFCUEXkyazksSv8pdTMAs9IucChvFmmq3 jJ2vlaz9lYt/lxN246fIVceckPMiUveimngvXZw21VOAhfQ+/sofXF8JCFv2mFcBDoa7eYob s0FLpmqFaeNRHAlzMWgSsP80qx5nWWEvRLdKWi533N2vC/EyunN3HcBwVrXH4hxRBMco3jvM m8VKLKao9wKj82qSivUnkPIwsAGNPdFoPbgghCQiBjBe6A75Z2xHFrzo7t1jg7nQfIyNC7ez MZBJ59sqA9EDMEJPlLNIeJmqslXPjmMFnE7Mby/+335WJYDulsRybN+W5rLT5aMvhC6x6POK z55fMNKrMASCzBJum2Fwjf/VnuGRYkhKCqqZ8gJ3OvmR50tInDV2jZ1DQgc3i550T5JDpToh dPBxZocIhzg+MBSRDXcJmHOx/7nQm3iQ6iLuwmXsRC6f5FbFefk9EjuTKcLMvBsEx+2DEx0E UnmJ4hVg7u1PQ+2Oy+Lh/opK/BDiqlQ8Pz2jiXv5xkECvr/3Sv59hlOCZMOaiLTTjtOIU7Tq 7ut6OL64oAq+zsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCghCj/CA/lc/LMthqQ773ga uB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseBfDXHA6m4B3mUTWo13nid 0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts6TZ+IrPOwT1hfB4WNC+X 2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiuQmt3yqrmN63V9wzaPhC+ xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKBTccu2AXJXWAE1Xjh6GOC 8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvFFFyAS0Nk1q/7EChPcbRb hJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh2YmnmLRTro6eZ/qYwWkC u8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRkF3TwgucpyPtcpmQtTkWS gDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0LLH63+BrrHasfJzxKXzqg rW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4vq7oFCPsOgwARAQABwsFl BBgBAgAPBQJVy5+RAhsMBQkJZgGAAAoJEE3eEPcA/4NagOsP/jPoIBb/iXVbM+fmSHOjEshl KMwEl/m5iLj3iHnHPVLBUWrXPdS7iQijJA/VLxjnFknhaS60hkUNWexDMxVVP/6lbOrs4bDZ NEWDMktAeqJaFtxackPszlcpRVkAs6Msn9tu8hlvB517pyUgvuD7ZS9gGOMmYwFQDyytpepo YApVV00P0u3AaE0Cj/o71STqGJKZxcVhPaZ+LR+UCBZOyKfEyq+ZN311VpOJZ1IvTExf+S/5 lqnciDtbO3I4Wq0ArLX1gs1q1XlXLaVaA3yVqeC8E7kOchDNinD3hJS4OX0e1gdsx/e6COvy qNg5aL5n0Kl4fcVqM0LdIhsubVs4eiNCa5XMSYpXmVi3HAuFyg9dN+x8thSwI836FoMASwOl C7tHsTjnSGufB+D7F7ZBT61BffNBBIm1KdMxcxqLUVXpBQHHlGkbwI+3Ye+nE6HmZH7IwLwV W+Ajl7oYF+jeKaH4DZFtgLYGLtZ1LDwKPjX7VAsa4Yx7S5+EBAaZGxK510MjIx6SGrZWBrrV TEvdV00F2MnQoeXKzD7O4WFbL55hhyGgfWTHwZ457iN9SgYi1JLPqWkZB0JRXIEtjd4JEQcx +8Umfre0Xt4713VxMygW0PnQt5aSQdMD58jHFxTk092mU+yIHj5LeYgvwSgZN4airXk5yRXl SE+xAvmumFBY Organization: Red Hat GmbH Message-ID: Date: Mon, 15 Jul 2019 16:40:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <46336efb-3243-0083-1d20-7e8578131679@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Mon, 15 Jul 2019 14:40:45 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 15.07.19 11:33, David Hildenbrand wrote: > On 11.07.19 20:21, Dave Hansen wrote: >> On 7/10/19 12:51 PM, Nitesh Narayan Lal wrote: >>> +static void bm_set_pfn(struct page *page) >>> +{ >>> + struct zone *zone = page_zone(page); >>> + int zone_idx = page_zonenum(page); >>> + unsigned long bitnr = 0; >>> + >>> + lockdep_assert_held(&zone->lock); >>> + bitnr = pfn_to_bit(page, zone_idx); >>> + /* >>> + * TODO: fix possible underflows. >>> + */ >>> + if (free_area[zone_idx].bitmap && >>> + bitnr < free_area[zone_idx].nbits && >>> + !test_and_set_bit(bitnr, free_area[zone_idx].bitmap)) >>> + atomic_inc(&free_area[zone_idx].free_pages); >>> +} >> >> Let's say I have two NUMA nodes, each with ZONE_NORMAL and ZONE_MOVABLE >> and each zone with 1GB of memory: >> >> Node: 0 1 >> NORMAL 0->1GB 2->3GB >> MOVABLE 1->2GB 3->4GB >> >> This code will allocate two bitmaps. The ZONE_NORMAL bitmap will >> represent data from 0->3GB and the ZONE_MOVABLE bitmap will represent >> data from 1->4GB. That's the result of this code: >> >>> + if (free_area[zone_idx].base_pfn) { >>> + free_area[zone_idx].base_pfn = >>> + min(free_area[zone_idx].base_pfn, >>> + zone->zone_start_pfn); >>> + free_area[zone_idx].end_pfn = >>> + max(free_area[zone_idx].end_pfn, >>> + zone->zone_start_pfn + >>> + zone->spanned_pages); >> >> But that means that both bitmaps will have space for PFNs in the other >> zone type, which is completely bogus. This is fundamental because the >> data structures are incorrectly built per zone *type* instead of per zone. >> > > I don't think it's incorrect, it's just not optimal in all scenarios. > E.g., in you example, this approach would "waste" 2 * 1GB of tracking > data for the wholes (2* 64bytes when using 1 bit for 2MB). > > FWIW, this is not a numa-specific thingy. We can have sparse zones > easily on single-numa systems. > > Node: 0 > NORMAL 0->1GB, 2->3GB > MOVABLE 1->2GB, 3->4GB > > So tracking it per zones instead instead of zone type is only one part > of the story. > Oh, and FWIW, in setups like Node: 0 1 NORMAL 4->5GB, 6->7GB 5->6GB, 8->9GB What Nitesh proposes is actually better. So it really depends on the use case - but in general sparsity is the issue. -- Thanks, David / dhildenb