From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@kernel.org>
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 40CC3C433EF
	for <linux-kernel@archiver.kernel.org>; Mon,  4 Jul 2022 15:00:34 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S234182AbiGDPAd (ORCPT <rfc822;linux-kernel@archiver.kernel.org>);
        Mon, 4 Jul 2022 11:00:33 -0400
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57324 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S230174AbiGDPAa (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 4 Jul 2022 11:00:30 -0400
Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6C5B62D4
        for <linux-kernel@vger.kernel.org>; Mon,  4 Jul 2022 08:00:28 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;
        d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version:
        References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:
        Content-Transfer-Encoding:Content-ID:Content-Description;
        bh=yswN5aZkyvlegWG7tn/cLii2U3IAmP4FdWDVkw8I23c=; b=SyYMOfELnNCGaaPbSWD/JGXhXh
        MLbsalnhhK7QuipbmZDNCWfxzN4mOdM23XricwOPKMP1kbKeEz577rXjrwsYlL4eNXSXunynR+U+y
        F7q6Sc79Rtf84OsBGBDMMY0c2HSXe2R+h4ix5JmhVcdihOb5KYZJ3l/5JU3O0Df+m99e0UiPMmUio
        udO0dfm8XWh2dI9jUCHOjqRTk7Iwwagrg1m/lLbaEixP+zGIafxWFFTtxoOKU6VCCuwzxnWkc9OCo
        OH2wGaAzUqCfTMw/t462zIW6fba7glnuRvORXn2vfBwaHyy5zVivgTMfZQ93jAhzgmyVFcXJHkxse
        0FHAad0g==;
Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux))
        id 1o8NYX-00HNZO-Kl; Mon, 04 Jul 2022 15:00:09 +0000
Date:   Mon, 4 Jul 2022 16:00:09 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc:     linux-mm@kvack.org, akpm@linux-foundation.org,
        Wei Xu <weixugc@google.com>, Huang Ying <ying.huang@intel.com>,
        Yang Shi <shy828301@gmail.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Tim C Chen <tim.c.chen@intel.com>,
        Michal Hocko <mhocko@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Hesham Almatary <hesham.almatary@huawei.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Alistair Popple <apopple@nvidia.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Johannes Weiner <hannes@cmpxchg.org>, jvgediya.oss@gmail.com
Subject: Re: [PATCH v8 00/12] mm/demotion: Memory tiers and demotion
Message-ID: <YsMAeU2fwEoysohr@casper.infradead.org>
References: <20220704070612.299585-1-aneesh.kumar@linux.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220704070612.299585-1-aneesh.kumar@linux.ibm.com>
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Jul 04, 2022 at 12:36:00PM +0530, Aneesh Kumar K.V wrote:
> * The current tier initialization code always initializes
>   each memory-only NUMA node into a lower tier.  But a memory-only
>   NUMA node may have a high performance memory device (e.g. a DRAM
>   device attached via CXL.mem or a DRAM-backed memory-only node on
>   a virtual machine) and should be put into a higher tier.
> 
> * The current tier hierarchy always puts CPU nodes into the top
>   tier. But on a system with HBM (e.g. GPU memory) devices, these
>   memory-only HBM NUMA nodes should be in the top tier, and DRAM nodes
>   with CPUs are better to be placed into the next lower tier.

These things that you identify as problems seem perfectly sensible to me.
Memory which is attached to this CPU has the lowest latency and should
be preferred over more remote memory, no matter its bandwidth.