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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3327CC433F5 for ; Mon, 18 Apr 2022 16:50:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346449AbiDRQx1 (ORCPT ); Mon, 18 Apr 2022 12:53:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346447AbiDRQxY (ORCPT ); Mon, 18 Apr 2022 12:53:24 -0400 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA3CD32EFF for ; Mon, 18 Apr 2022 09:50:36 -0700 (PDT) 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="245453342" X-IronPort-AV: E=Sophos;i="5.90,270,1643702400"; d="scan'208";a="245453342" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.