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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 9D9C9C433E3 for ; Mon, 10 Aug 2020 07:32:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5064D2073A for ; Mon, 10 Aug 2020 07:32:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="F5Je8ewD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5064D2073A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EA1A66B0003; Mon, 10 Aug 2020 03:32:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E514A6B0005; Mon, 10 Aug 2020 03:32:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D194F6B0006; Mon, 10 Aug 2020 03:32:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0164.hostedemail.com [216.40.44.164]) by kanga.kvack.org (Postfix) with ESMTP id BB0536B0003 for ; Mon, 10 Aug 2020 03:32:45 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 79FAF181AC9C6 for ; Mon, 10 Aug 2020 07:32:45 +0000 (UTC) X-FDA: 77133841890.13.duck06_2b0bb9f26fd8 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 5100F18140B60 for ; Mon, 10 Aug 2020 07:32:45 +0000 (UTC) X-HE-Tag: duck06_2b0bb9f26fd8 X-Filterd-Recvd-Size: 8848 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [205.139.110.61]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Mon, 10 Aug 2020 07:32:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597044764; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Pf2gnD93u5PiPmv+Ak0uYR+4wn4zwq2Nglh6AAI8C/w=; b=F5Je8ewD5CFjfunlGg2pYhsKVxXmGDX6pdik0wJZerM8x+jcB+kxPgbXsHwIEdyI2AG1s/ 4E/qNmszoJAR+1k6y9z1XofMRQxQiNIW+zhgtmThta2s/Bf3GSoZfbRp6ewdN6cSuQzm2Y PWoEvdMftH/IaPfReR2WFiA+hXBMqzU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-500-g7okM2B-NYy3RlJ4rDG8xA-1; Mon, 10 Aug 2020 03:32:26 -0400 X-MC-Unique: g7okM2B-NYy3RlJ4rDG8xA-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id BC5FA1009440; Mon, 10 Aug 2020 07:32:24 +0000 (UTC) Received: from [10.36.113.172] (ovpn-113-172.ams2.redhat.com [10.36.113.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id E447619D61; Mon, 10 Aug 2020 07:32:19 +0000 (UTC) Subject: Re: [PATCH] mm: sort freelist by rank number To: Pekka Enberg Cc: pullip.cho@samsung.com, Andrew Morton , "linux-mm@kvack.org" , LKML , hyesoo.yu@samsung.com, janghyuck.kim@samsung.com References: <1596435031-41837-1-git-send-email-pullip.cho@samsung.com> <5f41af0f-4593-3441-12f4-5b0f7e6999ac@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63W5Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAjwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat GmbH Message-ID: Date: Mon, 10 Aug 2020 09:32:18 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Rspamd-Queue-Id: 5100F18140B60 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 Content-Transfer-Encoding: quoted-printable 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 07.08.20 09:08, Pekka Enberg wrote: > Hi Cho and David, >=20 > On Mon, Aug 3, 2020 at 10:57 AM David Hildenbrand wr= ote: >> >> On 03.08.20 08:10, pullip.cho@samsung.com wrote: >>> From: Cho KyongHo >>> >>> LPDDR5 introduces rank switch delay. If three successive DRAM accesse= s >>> happens and the first and the second ones access one rank and the las= t >>> access happens on the other rank, the latency of the last access will >>> be longer than the second one. >>> To address this panelty, we can sort the freelist so that a specific >>> rank is allocated prior to another rank. We expect the page allocator >>> can allocate the pages from the same rank successively with this >>> change. It will hopefully improves the proportion of the consecutive >>> memory accesses to the same rank. >> >> This certainly needs performance numbers to justify ... and I am sorry= , >> "hopefully improves" is not a valid justification :) >> >> I can imagine that this works well initially, when there hasn't been a >> lot of memory fragmentation going on. But quickly after your system is >> under stress, I doubt this will be very useful. Proof me wrong. ;) >> >> ... I dislike this manual setting of "dram_rank_granule". Yet another = mm >> feature that can only be enabled by a magic command line parameter whe= re >> users have to guess the right values. >> >> (side note, there have been similar research approaches to improve >> energy consumption by switching off ranks when not needed). >=20 > I was thinking of the exact same thing. PALLOC [1] comes to mind, but > perhaps there are more recent ones? A more recent one is "Footprint-Based DIMM Hotplug" (https://dl.acm.org/doi/abs/10.1109/TC.2019.2945562), which triggers memory onlinng/offlining from the kernel to disable banks where possible (I don't think the approach is upstream material in that form). Also, I stumbled over "Towards Practical Page Placement for a Green Memory Manager" (https://ieeexplore.ieee.org/document/7397629), proposing an adaptive buddy allocator that tries to keep complete banks free in the buddy where possible. That approach sounded quite interesting while skimming over the paper. >=20 > I also dislike the manual knob, but is there a way for the OS to > detect this by itself? My (perhaps outdated) understanding was that > the DRAM address mapping scheme, for example, is not exposed to the > OS. I guess one universal approach is by measuring access times ... not what we might be looking for :) >=20 > I think having more knowledge of DRAM controller details in the OS > would be potentially beneficial for better page allocation policy, so > maybe try come up with something more generic, even if the fallback to > providing this information is a kernel command line option. >=20 > [1] http://cs-people.bu.edu/rmancuso/files/papers/palloc-rtas2014.pdf >=20 > - Pekka >=20 --=20 Thanks, David / dhildenb