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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD591C3ABC0 for ; Thu, 8 May 2025 15:12:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 34D356B000A; Thu, 8 May 2025 11:12:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2D4546B0082; Thu, 8 May 2025 11:12:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 14D8F6B0083; Thu, 8 May 2025 11:12:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id E99786B000A for ; Thu, 8 May 2025 11:12:50 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 5AE8457902 for ; Thu, 8 May 2025 15:12:52 +0000 (UTC) X-FDA: 83420082984.13.B514095 Received: from mail-il1-f180.google.com (mail-il1-f180.google.com [209.85.166.180]) by imf25.hostedemail.com (Postfix) with ESMTP id 47F82A0010 for ; Thu, 8 May 2025 15:12:50 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=gourry.net header.s=google header.b=YyQaA1Fo; dmarc=none; spf=pass (imf25.hostedemail.com: domain of gourry@gourry.net designates 209.85.166.180 as permitted sender) smtp.mailfrom=gourry@gourry.net ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1746717170; a=rsa-sha256; cv=none; b=afuXdmtqa2KV9AWjjKxcD/IwAxg/JOov/jgIMTvl6fG9v7y8+1X/GHSc3ht+PfrDQ17Lth 7eUNP6JD9hyo8typ7qhwPdxUSwtw5oeuFqjQ1fUP5mdGZ0gCliNE+sgmgQamBgGaPWNpAt J8phN1fkveNCpvotJELCuKj2SokFykc= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=gourry.net header.s=google header.b=YyQaA1Fo; dmarc=none; spf=pass (imf25.hostedemail.com: domain of gourry@gourry.net designates 209.85.166.180 as permitted sender) smtp.mailfrom=gourry@gourry.net ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1746717170; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=0GcWz7M9jCTD3vQ092kn0pMggWzRsyQcje+pdvcvTyU=; b=dm8hopuRbRpVfJLeN9ZKhcIxL/pSQOLNZi5IFaOIgk8t8uYjnVZWx/gALqeOr2+gxRv+RH fAJ6LfN3CRhKKYVbGa6w4x0EcOf/OZcHlK1fTGEFxP6FwBCQSz0AIPYyfvS11o3AiD6FH/ bZh6ebAJc1ERrNNbmmv2JCItPdW58iE= Received: by mail-il1-f180.google.com with SMTP id e9e14a558f8ab-3cfce97a3d9so8346285ab.2 for ; Thu, 08 May 2025 08:12:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gourry.net; s=google; t=1746717169; x=1747321969; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=0GcWz7M9jCTD3vQ092kn0pMggWzRsyQcje+pdvcvTyU=; b=YyQaA1FouD21t5vP0JaQG/R3nxqIhDVxmV7kgXUU/lOS66Gez+SeOJmkvOt8pthmhA StKOlBVnEJyjb+VNyi7cl+sd0o9HPxNFNgVo4PiNRgU2Ztw4XYc8pwNFwCpgYBQQfVJa 4/VzQMVxKWJVddxt58Czx0RT9tY1kBB+Z1dZcARxmpNT8jC+oUQlhbv3bpphRu3HYlVo lQmzxTFgn86oQ+RadzEzdJb0LY8oxazh3lbavO5QZBFx1HpQ1nTuRjc8PJaFeonklKya 9f0BtOe8pPEN8Qg0iJUlC5EIz0hx9hdPOco7pMpHl23cSvFi/ujErMxyv4XRxuvxgYpE oiFg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1746717169; x=1747321969; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=0GcWz7M9jCTD3vQ092kn0pMggWzRsyQcje+pdvcvTyU=; b=u+LKIilQWQ1flqeqOpIdTvk9CFr5Sqo1vR/8H2+JV14/NmJCE6JWC0tbZNh/19TQ/H WXVLzoaDrFSNFFktubDOi+RHgRZj2XHNTOuCmE3K9BQE0h+U2LeSi819Z/lDj2LG25dp gJB5MPEL4VDbOyPM1nO+luyJYFeVFD03csnE8TuEavTeS/WWQf8IEIHazRZKvYRbZRk8 nAfaTwRq/28r+5CcEQKKOGU5LgOGkiRx/YPJzeflSXoSvZoYxzSFxMZDDskKRl/+x1sV pXOOdra0pwhREE9zjq8dAmfFurGEo/ajKuDENeN04zBUMATqeeChBLROW3cu9xLalOpp 2pcA== X-Forwarded-Encrypted: i=1; AJvYcCXEIgktALgNj3gnrvOUuUZWZXXN0tGOBpsjhHkyybJhSxKhP5F0CGPBIuJPWh1zBmS+t9yQ5lMeIw==@kvack.org X-Gm-Message-State: AOJu0YwqAYNa9qkS4/L5e6azTVUxUtIL5MLZzniM80F1dqaYraGWf0KX gwfh5d7HzVieDSJzXu1MXGkpxiN03oZ/goHjBYznswmAtyq9Fn64DnA8nkM4CaOQZwUr5SrA72G x X-Gm-Gg: ASbGncsehnhBLZhY9YZ6pgHH9tDFX+JkCOBKvwxL3JS01sAZVitmQvjGEmbkMKBTtjV CeBr/kmbXUhyyIe7VrTpTMH8ct48gWDVzLGnFvySFZGKImlRNVVeQiTLL8NSqEezFdSUzQFa3bK JVDf0eHsBrLeqxwUsZHQXWrkos0Ef5wcTc9vc8f9ijf4COfEghKDvqCoiXc89lxxzZ53HE6Yy1g y3W4uYX5dazBBogXCI8ChAfLChwYwZ5rCZtYpFmk8xR+rtofMC4h05lTuNjwu90MBVylmzUvOtO SY9B7IBK6JxkigVJeNySI3TIEKNCtInR4tPKJuzuWPXOFwOMpM/jJnLI8xaBwI2/DRQfyqhEwYh eHl8oT+8TUsLnKpkpWF1t X-Google-Smtp-Source: AGHT+IFrmotMhA/nMZAIEBB7GeHwIixjZIq4w08j6/K6MLvI6ZRzQvIIQBKip5mAFrzBQzYq229QKA== X-Received: by 2002:a05:6214:e8c:b0:6f5:e0c:b203 with SMTP id 6a1803df08f44-6f5429e89afmr115651736d6.11.1746717158264; Thu, 08 May 2025 08:12:38 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F (pool-96-255-20-42.washdc.ftas.verizon.net. [96.255.20.42]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6f6e3a60eaesm705496d6.122.2025.05.08.08.12.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 May 2025 08:12:37 -0700 (PDT) Date: Thu, 8 May 2025 11:12:35 -0400 From: Gregory Price To: Rakie Kim Cc: joshua.hahnjy@gmail.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, dan.j.williams@intel.com, ying.huang@linux.alibaba.com, kernel_team@skhynix.com, honggyu.kim@sk.com, yunjeong.mun@sk.com Subject: Re: [RFC] Add per-socket weight support for multi-socket systems in weighted interleave Message-ID: References: <20250508063042.210-1-rakie.kim@sk.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250508063042.210-1-rakie.kim@sk.com> X-Rspam-User: X-Rspamd-Queue-Id: 47F82A0010 X-Rspamd-Server: rspam04 X-Stat-Signature: fdiyo1wx3mfh677xqdnrn36u5krxxdic X-HE-Tag: 1746717170-58043 X-HE-Meta: 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 ccFOalxN x4EUu9jrIxN1uapCbEKwOQhD7zh+Ipu0Zlp2NW4IkX3MwqCOq+ZB3gy8aZDX3qzSo0flUDIoEzM8FAsg1b9wp2G/W77zTa3oJFYMt9EONjgvWwiddrt7zZQgVzwUKB6ag6xpM+HThBnRMLaf2c9Mt4fgQAhoIAj7Tz0nsWNutGr6Kig/Y1AWtEuVfNLOos6TQlhvPLItoA5fYtjdWtXCj8GZ4eOmAMINv5rtmnRccDMbyzakN5/vG7NqkDUESElBsvcMjsOL/9HXzTPmdHe6oGvk059RKRTNvausBAlCoNUJHruPQ93nyhG5swv+U/FL1HpDAk+N2cyh7XtaQ5NReB4QAfG3FmAdcOCRjh7Y1xRxFJKBAMhU1b8fmCnrN68tI4jmxpCpGfONVj/jTTN+OfjiJgnUxHhEvvNMOD4zYwQ0ucI/PETc2I52GSJhUA3EahRom5NROmvw3Hwo= 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: List-Subscribe: List-Unsubscribe: On Thu, May 08, 2025 at 03:30:36PM +0900, Rakie Kim wrote: > On Wed, 7 May 2025 12:38:18 -0400 Gregory Price wrote: > > The proposed design is completely optional and isolated: it retains the > existing flat weight model as-is and activates the source-aware behavior only > when 'multi' mode is enabled. The complexity is scoped entirely to users who > opt into this mode. > I get what you're going for, just expressing my experience around this issue specifically. The lack of enthusiasm for solving the cross-socket case, and thus reduction from a 2D array to a 1D array, was because reasoning about interleave w/ cross-socket interconnects is not really feasible with the NUMA abstraction. Cross-socket interconnects are "Invisible" but have real performance implications. Unless we have a way to: 1) Represent the topology, AND 2) A way to get performance about that topology It's not useful. So NUMA is an incomplete (if not wrong) tool for this. Additionally - reacting to task migration is not a real issue. If you're deploying an allocation strategy, you probably don't want your task migrating away from the place where you just spent a bunch of time allocating based on some existing strategy. So the solution is: don't migrate, and if you do - don't use cross-socket interleave. Maybe if we solve the first half of this we can take a look at the task migration piece again, but I wouldn't try to solve for migration. At the same time we were discussing this, we were also discussing how to do external task-mempolicy modifications - which seemed significantly more useful, but ultimately more complex and without sufficient interested parties / users. ~Gregory