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 D0076C433EF for ; Tue, 26 Apr 2022 09:10:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 626E96B0073; Tue, 26 Apr 2022 05:10:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5D7216B0074; Tue, 26 Apr 2022 05:10:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 49E326B0075; Tue, 26 Apr 2022 05:10:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.26]) by kanga.kvack.org (Postfix) with ESMTP id 3838A6B0073 for ; Tue, 26 Apr 2022 05:10:13 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 0B59880C47 for ; Tue, 26 Apr 2022 09:10:13 +0000 (UTC) X-FDA: 79398458706.23.3D6259D Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf23.hostedemail.com (Postfix) with ESMTP id D8DA514004B for ; Tue, 26 Apr 2022 09:10:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650964212; x=1682500212; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version:content-transfer-encoding; bh=mhc1LkdFmJv5cdHaRlQmMd4IHZo0mxKiF8Rnx8DSyb4=; b=ZecLscP5kxhul5A62NKCZuZluUDOkj8GqvlplYQlNh6VAViN2knCpJdX cF0p9Xb6u/l5QYIGuA3vDwFT5mXX6rpF4u7bxI/aPkdgZrg6P9suioNGU 9cuk+dSpcwkvSXiLrrisy1wEA1Wbz6X446Yx56omGFtKms38f/OPgUCBe rkcMsZpNmNxBmAiklE2V2OjdXKU+tYmVUPgFwRH29DLtOQR9A8x8d8Wez c8+fqVF60tLRrh4V9yLn3umhQGhligHnZ9e8wTaDLoB1Sgddq9FoUQFAC gEYbotwmb195nt9gU/ZF3LxWnygMpSe/wlc6c6Amm7/V5szn4UkjoB7af w==; X-IronPort-AV: E=McAfee;i="6400,9594,10328"; a="328451860" X-IronPort-AV: E=Sophos;i="5.90,290,1643702400"; d="scan'208";a="328451860" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Apr 2022 02:10:10 -0700 X-IronPort-AV: E=Sophos;i="5.90,290,1643702400"; d="scan'208";a="532564643" Received: from yyu16-mobl.ccr.corp.intel.com ([10.254.212.128]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Apr 2022 02:10:07 -0700 Message-ID: <8cd54998029dd59dc2f6a04b698f75df021294c2.camel@intel.com> Subject: Re: [PATCH v3 0/7] mm: demotion: Introduce new node state N_DEMOTION_TARGETS From: "ying.huang@intel.com" To: Aneesh Kumar K V , Jagdish Gediya Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, baolin.wang@linux.alibaba.com, dave.hansen@linux.intel.com, shy828301@gmail.com, weixugc@google.com, gthelen@google.com, dan.j.williams@intel.com Date: Tue, 26 Apr 2022 17:10:04 +0800 In-Reply-To: <63b0c4ab-861c-3d07-4912-e6cd842d0bfd@linux.ibm.com> References: <20220422195516.10769-1-jvgediya@linux.ibm.com> <4b986b46afb2fe888c127d8758221d0f0d3ec55f.camel@intel.com> <085260285e48093f48d889994aaa500a78577bf2.camel@intel.com> <63b0c4ab-861c-3d07-4912-e6cd842d0bfd@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.3-1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D8DA514004B X-Stat-Signature: foy3i4bhn98odywm5y81jk8dkn6z1ziy Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=ZecLscP5; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf23.hostedemail.com: domain of ying.huang@intel.com has no SPF policy when checking 134.134.136.100) smtp.mailfrom=ying.huang@intel.com X-Rspam-User: X-HE-Tag: 1650964206-206067 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 Tue, 2022-04-26 at 14:37 +0530, Aneesh Kumar K V wrote: > On 4/26/22 1:25 PM, ying.huang@intel.com wrote: > > On Mon, 2022-04-25 at 16:45 +0530, Jagdish Gediya wrote: > > > On Sun, Apr 24, 2022 at 11:19:53AM +0800, ying.huang@intel.com wrote: > > > > On Sat, 2022-04-23 at 01:25 +0530, Jagdish Gediya wrote: > > > > > Some systems(e.g. PowerVM) can have both DRAM(fast memory) only > > > > > NUMA node which are N_MEMORY and slow memory(persistent memory) > > > > > only NUMA node which are also N_MEMORY. As the current demotion > > > > > target finding algorithm works based on N_MEMORY and best distance, > > > > > it will choose DRAM only NUMA node as demotion target instead of > > > > > persistent memory node on such systems. If DRAM only NUMA node is > > > > > filled with demoted pages then at some point new allocations can > > > > > start falling to persistent memory, so basically cold pages are in > > > > > fast memor (due to demotion) and new pages are in slow memory, this > > > > > is why persistent memory nodes should be utilized for demotion and > > > > > dram node should be avoided for demotion so that they can be used > > > > > for new allocations. > > > > > > > > > > Current implementation can work fine on the system where the memory > > > > > only numa nodes are possible only for persistent/slow memory but it > > > > > is not suitable for the like of systems mentioned above. > > > > > > > > Can you share the NUMA topology information of your machine? And the > > > > demotion order before and after your change? > > > > > > > > Whether it's good to use the PMEM nodes as the demotion targets of the > > > > DRAM-only node too? > > > > > > $ numactl -H > > > available: 2 nodes (0-1) > > > node 0 cpus: 0 1 2 3 4 5 6 7 > > > node 0 size: 14272 MB > > > node 0 free: 13392 MB > > > node 1 cpus: > > > node 1 size: 2028 MB > > > node 1 free: 1971 MB > > > node distances: > > > node 0 1 > > >    0: 10 40 > > >    1: 40 10 > > > > > > 1) without N_DEMOTION_TARGETS patch series, 1 is demotion target > > >     for 0 even when 1 is DRAM node and there is no demotion targets for 1. > > > > > > $ cat /sys/bus/nd/devices/dax0.0/target_node > > > 2 > > > $ > > > # cd /sys/bus/dax/drivers/ > > > :/sys/bus/dax/drivers# ls > > > device_dax kmem > > > :/sys/bus/dax/drivers# cd device_dax/ > > > :/sys/bus/dax/drivers/device_dax# echo dax0.0 > unbind > > > :/sys/bus/dax/drivers/device_dax# echo dax0.0 > ../kmem/new_id > > > :/sys/bus/dax/drivers/device_dax# numactl -H > > > available: 3 nodes (0-2) > > > node 0 cpus: 0 1 2 3 4 5 6 7 > > > node 0 size: 14272 MB > > > node 0 free: 13380 MB > > > node 1 cpus: > > > node 1 size: 2028 MB > > > node 1 free: 1961 MB > > > node 2 cpus: > > > node 2 size: 0 MB > > > node 2 free: 0 MB > > > node distances: > > > node 0 1 2 > > >    0: 10 40 80 > > >    1: 40 10 80 > > >    2: 80 80 10 > > > > > > > This looks like a virtual machine, not a real machine. That's > > unfortunate. I am looking forward to a real issue, not a theoritical > > possible issue. > > > > This is the source of confusion i guess. A large class of ppc64 systems > are virtualized. The firmware include a hypervisor (PowerVM) and end > user creates guest (aka LPAR) on them. That is the way end user will use > this system. There is no baremetal access on this (There is an openpower > variant, but all new systems built by IBM these days do have PowerVM on > them). > > > So this is not a theoretical possibility. > Now I get it. Thanks for detailed explanation. Best Regards, Huang, Ying