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 02AD2C433F5 for ; Mon, 18 Apr 2022 16:50:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4DFB48D0019; Mon, 18 Apr 2022 12:50:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 48DA28D0013; Mon, 18 Apr 2022 12:50:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 355658D0019; Mon, 18 Apr 2022 12:50:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id 25F948D0013 for ; Mon, 18 Apr 2022 12:50:39 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id E198B244A7 for ; Mon, 18 Apr 2022 16:50:38 +0000 (UTC) X-FDA: 79370588556.21.5F0257A Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf15.hostedemail.com (Postfix) with ESMTP id A2462A0003 for ; Mon, 18 Apr 2022 16:50:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650300637; x=1681836637; h=message-id:date:mime-version:to:references:from:subject: in-reply-to:content-transfer-encoding; bh=T9DgsGykPJu/61nxfr6AZYfMrvU5yqC0wpyU4UQckBs=; b=kbLypj4vUoXGNLt9eyOuZxrdqeuIKOvPfDhlIPpvgdMuY2aV8mBViOL/ CrS863w/iBoECNIYkT+Rib5LHihcT9Z805geve4zYt4sD2KzwbSmPh4pM ydtukVBjM1rvDI3al2Q66ZzrGKlR+4u1+qT6gXmx3nd/ZGq4XVHv1b1mN /UNdrODQEdkrjVrM7psEHpynhwxFho6+6bi0+L4yxw6XSbBxZo7C3DTuG +xrvwRHoQPlxye5UHiMMWtwcH0fOTAv8UX3RLVH6QtZa0fm0zoJ+lMHa+ uBcW5hFQ6NZRN87X2MAdTe9TesE+OpPZvfrJCjpJF0bqchE1D1QI3UuGs Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10321"; a="263025269" X-IronPort-AV: E=Sophos;i="5.90,270,1643702400"; d="scan'208";a="263025269" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Apr 2022 09:50:35 -0700 X-IronPort-AV: E=Sophos;i="5.90,270,1643702400"; d="scan'208";a="554310652" Received: from cebrown-mobl.amr.corp.intel.com (HELO [10.212.18.136]) ([10.212.18.136]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Apr 2022 09:50:34 -0700 Message-ID: <9961bda1-687a-a681-743e-7eb7b9f6f751@intel.com> Date: Mon, 18 Apr 2022 09:50:33 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Content-Language: en-US To: linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org, rientjes@google.com, yosryahmed@google.com, hannes@cmpxchg.org, shakeelb@google.com, dave.hansen@linux.intel.com, tim.c.chen@linux.intel.com, roman.gushchin@linux.dev, gthelen@google.com, a.manzanares@samsung.com, heekwon.p@samsung.com, gim.jongmin@samsung.com, linux-kernel@vger.kernel.org References: <20220416053902.68517-1-dave@stgolabs.net> <20220417034932.jborenmvfbqrfhlj@offworld> <20220418164503.jfips3aiwhnlfjrq@offworld> From: Dave Hansen Subject: Re: [PATCH 6/6] mm/migrate: export whether or not node is toptier in sysf In-Reply-To: <20220418164503.jfips3aiwhnlfjrq@offworld> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: aai3z4kmdsik4zum6qbebxw1ki4xsi8j X-Rspam-User: Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=kbLypj4v; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf15.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 134.134.136.24) smtp.mailfrom=dave.hansen@intel.com X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A2462A0003 X-HE-Tag: 1650300637-589686 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 4/18/22 09:45, Davidlohr Bueso wrote: > On Mon, 18 Apr 2022, Dave Hansen wrote: >> On 4/16/22 20:49, Davidlohr Bueso wrote: >>> This allows userspace to know if the node is considered fast >>> memory (with CPUs attached to it). While this can be already >>> derived without a new file, this helps further encapsulate the >>> concept. >> >> What is userspace supposed to *do* with this, though? > > This came as a scratch to my own itch. I wanted to start testing > more tiering patches overall that I see pop up, and wanted a way > to differentiate the slow vs the fast memories in order to better > configure workload(s) working set sizes beyond what is your typical > grep MemTotal /proc/meminfo. If there is a better way I'm all > for it. But how does this help you? Does it save you a few lines in a shell script to find the nodes that have memory and CPUs? >> Isn't it just asking for trouble to add (known) redundancy to the ABI? >> It seems like a recipe for future inconsistency. > > Perhaps. It was mostly about the fact that the notion of top tier > could also change as technology evolves. It seems like something arbitrary that everyone will just disagree on. I think we should try to stick to cold, hard facts as must as possible rather than trying to have the *kernel* dictate as a policy what is fast versus slow.