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 B02A7C433EF for ; Sun, 24 Apr 2022 03:02:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 10B556B0074; Sat, 23 Apr 2022 23:02:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0B9706B0075; Sat, 23 Apr 2022 23:02:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F12A56B0078; Sat, 23 Apr 2022 23:02:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.a.hostedemail.com [64.99.140.24]) by kanga.kvack.org (Postfix) with ESMTP id E51826B0074 for ; Sat, 23 Apr 2022 23:02:54 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id A79292149C for ; Sun, 24 Apr 2022 03:02:54 +0000 (UTC) X-FDA: 79390275468.22.29E061E Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by imf17.hostedemail.com (Postfix) with ESMTP id D0D7040031 for ; Sun, 24 Apr 2022 03:02:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650769373; x=1682305373; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version:content-transfer-encoding; bh=Ux9PsAQmdWKorvAm6+E36dUqx1AaTnYpTj72E3+/dCk=; b=n8+tGcF7TQnPcocaJo+q07HpYJezRXIgZaNqJ8s4/6EF2jvDqstjqzOk TqE0a0uv0WXawBJW1eonFfL4sQn1Gg8kP65dcwo4XlDTXL0oljHthvENq Cn0XL9spGRCfPWw6kKi7l3GI/OtW4IVRmYAZML7BbN62/mql2LArDEMmZ kPR3f/B2rLsAeRiq2A8JqIacjfFQirWbaeommWbAZplnEPZ6/FA8ZqXhA v03sgIWqSQw5AwhdQrzpVw0M+SPq6r0LFPLpKRoPE6ZWq7DEEAc5qxJB1 MhywSPxPO0K/+L1ScU1cho18ssM3eEkNV7xhNX4r4r81PtUjWLT/pyk9n g==; X-IronPort-AV: E=McAfee;i="6400,9594,10326"; a="246895458" X-IronPort-AV: E=Sophos;i="5.90,285,1643702400"; d="scan'208";a="246895458" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Apr 2022 20:02:52 -0700 X-IronPort-AV: E=Sophos;i="5.90,285,1643702400"; d="scan'208";a="557093768" Received: from dafeixu-mobl1.ccr.corp.intel.com ([10.254.212.194]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Apr 2022 20:02:49 -0700 Message-ID: <200e95cf36c1642512d99431014db8943fed715d.camel@intel.com> Subject: Re: [PATCH v2 0/5] mm: demotion: Introduce new node state N_DEMOTION_TARGETS From: "ying.huang@intel.com" To: Jagdish Gediya , Wei Xu , Yang Shi , Dave Hansen , Dan Williams , Davidlohr Bueso Cc: Linux MM , Linux Kernel Mailing List , Andrew Morton , "Aneesh Kumar K.V" , Baolin Wang , Greg Thelen , MichalHocko , Brice Goglin Date: Sun, 24 Apr 2022 11:02:47 +0800 In-Reply-To: References: <610ccaad03f168440ce765ae5570634f3b77555e.camel@intel.com> <8e31c744a7712bb05dbf7ceb2accf1a35e60306a.camel@intel.com> <78b5f4cfd86efda14c61d515e4db9424e811c5be.camel@intel.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.3-1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=n8+tGcF7; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf17.hostedemail.com: domain of ying.huang@intel.com has no SPF policy when checking 134.134.136.126) smtp.mailfrom=ying.huang@intel.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D0D7040031 X-Rspam-User: X-Stat-Signature: aix5bbntopnhrqhacwedwponbgx4r45s X-HE-Tag: 1650769368-758448 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: Hi, All, On Fri, 2022-04-22 at 16:30 +0530, Jagdish Gediya wrote: [snip] > I think it is necessary to either have per node demotion targets > configuration or the user space interface supported by this patch > series. As we don't have clear consensus on how the user interface > should look like, we can defer the per node demotion target set > interface to future until the real need arises. > > Current patch series sets N_DEMOTION_TARGET from dax device kmem > driver, it may be possible that some memory node desired as demotion > target is not detected in the system from dax-device kmem probe path. > > It is also possible that some of the dax-devices are not preferred as > demotion target e.g. HBM, for such devices, node shouldn't be set to > N_DEMOTION_TARGETS. In future, Support should be added to distinguish > such dax-devices and not mark them as N_DEMOTION_TARGETS from the > kernel, but for now this user space interface will be useful to avoid > such devices as demotion targets. > > We can add read only interface to view per node demotion targets > from /sys/devices/system/node/nodeX/demotion_targets, remove > duplicated /sys/kernel/mm/numa/demotion_target interface and instead > make /sys/devices/system/node/demotion_targets writable. > > Huang, Wei, Yang, > What do you suggest? We cannot remove a kernel ABI in practice. So we need to make it right at the first time. Let's try to collect some information for the kernel ABI definitation. The below is just a starting point, please add your requirements. 1. Jagdish has some machines with DRAM only NUMA nodes, but they don't want to use that as the demotion targets. But I don't think this is a issue in practice for now, because demote-in-reclaim is disabled by default. 2. For machines with PMEM installed in only 1 of 2 sockets, for example, Node 0 & 2 are cpu + dram nodes and node 1 are slow memory node near node 0, available: 3 nodes (0-2) node 0 cpus: 0 1 node 0 size: n MB node 0 free: n MB node 1 cpus: node 1 size: n MB node 1 free: n MB node 2 cpus: 2 3 node 2 size: n MB node 2 free: n MB node distances: node 0 1 2 0: 10 40 20 1: 40 10 80 2: 20 80 10 We have 2 choices, a) node demotion targets 0 1 2 1 b) node demotion targets 0 1 2 X a) is good to take advantage of PMEM. b) is good to reduce cross-socket traffic. Both are OK as defualt configuration. But some users may prefer the other one. So we need a user space ABI to override the default configuration. 3. For machines with HBM (High Bandwidth Memory), as in https://lore.kernel.org/lkml/39cbe02a-d309-443d-54c9-678a0799342d@gmail.com/ > [1] local DDR = 10, remote DDR = 20, local HBM = 31, remote HBM = 41 Although HBM has better performance than DDR, in ACPI SLIT, their distance to CPU is longer. We need to provide a way to fix this. The user space ABI is one way. The desired result will be to use local DDR as demotion targets of local HBM. Best Regards, Huang, Ying