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 0D092ECAAD5 for ; Fri, 2 Sep 2022 09:05:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7F32B8D001A; Fri, 2 Sep 2022 05:04:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7A2258D0014; Fri, 2 Sep 2022 05:04:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 66AAF8D001A; Fri, 2 Sep 2022 05:04:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 5705B8D0014 for ; Fri, 2 Sep 2022 05:04:59 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 1D3671211DF for ; Fri, 2 Sep 2022 09:04:59 +0000 (UTC) X-FDA: 79866560718.30.395357C Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by imf30.hostedemail.com (Postfix) with ESMTP id 532BE8007A for ; Fri, 2 Sep 2022 09:04:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1662109498; x=1693645498; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=+uvbB2ryl//T87TRTZlLEPk15pWjZP7QXw7HS4tbRE8=; b=fgn4R/ykFNd4vqS1WVY/A4Rn89uYw7uRMwsiQt00FIRWUGACzzQVsGGA RmfJZtkiKWnMYqIBmWFeRaOrv67CBhLxossHAP6c5Pl5wFWPnuhbSyBME uKT2EHNZ0fRptvryDb5WPqFQwIBm26IY4pCvO2/LEvqOUoBsIjByNVZtJ KZHh1FhWMboJofX/rLMvQHnGeGNK8a57jy/N0DK8wDefPeQTaCM5KnKP5 yAz957Sozeu/64gmN8BkdmZKv4oJLxA3Gmkyulm0IjzgWKuw2Y3OCqJDS +zGVGGrVeiaVMNoo9Hwa6wstXcwM3J9W3KfG9Fpp5q6W/6JDvI5hkI8hd A==; X-IronPort-AV: E=McAfee;i="6500,9779,10457"; a="357656258" X-IronPort-AV: E=Sophos;i="5.93,283,1654585200"; d="scan'208";a="357656258" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2022 02:04:57 -0700 X-IronPort-AV: E=Sophos;i="5.93,283,1654585200"; d="scan'208";a="941219190" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2022 02:04:52 -0700 From: "Huang, Ying" To: Aneesh Kumar K V Cc: Wei Xu , Johannes Weiner , Linux MM , Andrew Morton , Yang Shi , Davidlohr Bueso , Tim C Chen , Michal Hocko , Linux Kernel Mailing List , Hesham Almatary , Dave Hansen , Jonathan Cameron , Alistair Popple , Dan Williams , jvgediya.oss@gmail.com, Bharata B Rao , Greg Thelen , Greg Kroah-Hartman , "Rafael J. Wysocki" Subject: Re: [PATCH v3 updated] mm/demotion: Expose memory tier details via sysfs References: <20220830081736.119281-1-aneesh.kumar@linux.ibm.com> <87tu5rzigc.fsf@yhuang6-desk2.ccr.corp.intel.com> <87pmgezkhp.fsf@yhuang6-desk2.ccr.corp.intel.com> <87fshaz63h.fsf@yhuang6-desk2.ccr.corp.intel.com> <698120ce-d4df-3d13-dea9-a8f5c298783c@linux.ibm.com> <87bkryz4nh.fsf@yhuang6-desk2.ccr.corp.intel.com> <2b4ddc45-74ae-27df-d973-6724f61f4e18@linux.ibm.com> <877d2mz3c1.fsf@yhuang6-desk2.ccr.corp.intel.com> <45488760-02b5-115b-c16d-5219303f2f33@linux.ibm.com> <871qsuyzr2.fsf@yhuang6-desk2.ccr.corp.intel.com> <672e528d-40b7-fc12-9b0c-1591d586c079@linux.ibm.com> Date: Fri, 02 Sep 2022 17:04:51 +0800 In-Reply-To: <672e528d-40b7-fc12-9b0c-1591d586c079@linux.ibm.com> (Aneesh Kumar K. V.'s message of "Fri, 2 Sep 2022 14:18:40 +0530") Message-ID: <87wnamxi30.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662109498; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=etKs7aWHeFntjBxcIwXO/lQbszFdZrapXCUwr/Yj7DE=; b=M8KpoFx98eCNSojot41QlgvVZc0N+2u+u2ml6hmH6z7Ls15kUFsUR42AqckeAcrzrHhgBD Kg6nmMvxinRz8N9mpDlo1cL3f6dvFN/V6NLv3xoyAXiIWpuYhOrI5/XYM1/uvxyOB3MshM Alt2FU4jrf5HANRgvkgz2GhvNass3/o= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b="fgn4R/yk"; spf=softfail (imf30.hostedemail.com: 134.134.136.31 is neither permitted nor denied by domain of ying.huang@intel.com) smtp.mailfrom=ying.huang@intel.com; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662109498; a=rsa-sha256; cv=none; b=3VrXMVJqVFSRt4wI6XcvkocnCMNVr4KFPCbM8uIz4QOPk0mQaBbNKUksP+TdOl9WYe4/0u fHwvgSThYTywYzdS0hu139tYVaYaFKUtYq2BSWmi1QyKJ+Pt4fSeqq+3rUvnczDslZKEbS cT0ecbEnVN47dJjWzSQHoMRYr/3m/aI= X-Stat-Signature: q348yupbkpey3k5u76735hcpyx6qodn8 X-Rspamd-Queue-Id: 532BE8007A Authentication-Results: imf30.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b="fgn4R/yk"; spf=softfail (imf30.hostedemail.com: 134.134.136.31 is neither permitted nor denied by domain of ying.huang@intel.com) smtp.mailfrom=ying.huang@intel.com; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none) X-Rspamd-Server: rspam12 X-Rspam-User: X-HE-Tag: 1662109498-358598 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: Aneesh Kumar K V writes: > On 9/2/22 1:27 PM, Huang, Ying wrote: >> Wei Xu writes: >> >>> On Thu, Sep 1, 2022 at 11:44 PM Aneesh Kumar K V >>> wrote: >>>> >>>> On 9/2/22 12:10 PM, Huang, Ying wrote: >>>>> Aneesh Kumar K V writes: >>>>> >>>>>> On 9/2/22 11:42 AM, Huang, Ying wrote: >>>>>>> Aneesh Kumar K V writes: >>>>>>> >>>>>>>> On 9/2/22 11:10 AM, Huang, Ying wrote: >>>>>>>>> Aneesh Kumar K V writes: >>>>>>>>> >>>>>>>>>> On 9/2/22 10:39 AM, Wei Xu wrote: >>>>>>>>>>> On Thu, Sep 1, 2022 at 5:33 PM Huang, Ying wrote: >>>>>>>>>>>> >>>>>>>>>>>> Aneesh Kumar K V writes: >>>>>>>>>>>> >>>>>>>>>>>>> On 9/1/22 12:31 PM, Huang, Ying wrote: >>>>>>>>>>>>>> "Aneesh Kumar K.V" writes: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> This patch adds /sys/devices/virtual/memory_tiering/ where all memory tier >>>>>>>>>>>>>>> related details can be found. All allocated memory tiers will be listed >>>>>>>>>>>>>>> there as /sys/devices/virtual/memory_tiering/memory_tierN/ >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> The nodes which are part of a specific memory tier can be listed via >>>>>>>>>>>>>>> /sys/devices/virtual/memory_tiering/memory_tierN/nodes >>>>>>>>>>>>>> >>>>>>>>>>>>>> I think "memory_tier" is a better subsystem/bus name than >>>>>>>>>>>>>> memory_tiering. Because we have a set of memory_tierN devices inside. >>>>>>>>>>>>>> "memory_tier" sounds more natural. I know this is subjective, just my >>>>>>>>>>>>>> preference. >>>>>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> I missed replying to this earlier. I will keep memory_tiering as subsystem name in v4 >>>>>>>>>> because we would want it to a susbsystem where all memory tiering related details can be found >>>>>>>>>> including memory type in the future. This is as per discussion >>>>>>>>>> >>>>>>>>>> https://lore.kernel.org/linux-mm/CAAPL-u9TKbHGztAF=r-io3gkX7gorUunS2UfstudCWuihrA=0g@mail.gmail.com >>>>>>>>> >>>>>>>>> I don't think that it's a good idea to mix 2 types of devices in one >>>>>>>>> subsystem (bus). If my understanding were correct, that breaks the >>>>>>>>> driver core convention. >>>>>>>>> >>>>>>>> >>>>>>>> All these are virtual devices .I am not sure i follow what you mean by 2 types of devices. >>>>>>>> memory_tiering is a subsystem that represents all the details w.r.t memory tiering. It shows >>>>>>>> details of memory tiers and can possibly contain details of different memory types . >>>>>>> >>>>>>> IMHO, memory_tier and memory_type are 2 kind of devices. They have >>>>>>> almost totally different attributes (sysfs file). So, we should create >>>>>>> 2 buses for them. Each has its own attribute group. "virtual" itself >>>>>>> isn't a subsystem. >>>>>> >>>>>> Considering both the details are related to memory tiering, wouldn't it be much simpler we consolidate >>>>>> them within the same subdirectory? I am still not clear why you are suggesting they need to be in different >>>>>> sysfs hierarchy. It doesn't break any driver core convention as you mentioned earlier. >>>>>> >>>>>> /sys/devices/virtual/memory_tiering/memory_tierN >>>>>> /sys/devices/virtual/memory_tiering/memory_typeN >>>>> >>>>> I think we should add >>>>> >>>>> /sys/devices/virtual/memory_tier/memory_tierN >>>>> /sys/devices/virtual/memory_type/memory_typeN >>>>> >>>> >>>> I am trying to find if there is a technical reason to do the same? >>>> >>>>> I don't think this is complex. Devices of same bus/subsystem should >>>>> have mostly same attributes. This is my understanding of driver core >>>>> convention. >>>>> >>>> >>>> I was not looking at this from code complexity point. Instead of having multiple directories >>>> with details w.r.t memory tiering, I was looking at consolidating the details >>>> within the directory /sys/devices/virtual/memory_tiering. (similar to all virtual devices >>>> are consolidated within /sys/devics/virtual/). >>>> >>>> -aneesh >>> >>> Here is an example of /sys/bus/nd/devices (I know it is not under >>> /sys/devices/virtual, but it can still serve as a reference): >>> >>> ls -1 /sys/bus/nd/devices >>> >>> namespace2.0 >>> namespace3.0 >>> ndbus0 >>> nmem0 >>> nmem1 >>> region0 >>> region1 >>> region2 >>> region3 >>> >>> So I think it is not unreasonable if we want to group memory tiering >>> related interfaces within a single top directory. >> >> Thanks for pointing this out. My original understanding of driver core >> isn't correct. >> >> But I still think it's better to separate instead of mixing memory_tier >> and memory_type. Per my understanding, memory_type shows information >> (abstract distance, latency, bandwidth, etc.) of memory types (and >> nodes), it can be useful even without memory tiers. That is, memory >> types describes the physical characteristics, while memory tier reflects >> the policy. >> > > The latency and bandwidth details are already exposed via > > /sys/devices/system/node/nodeY/access0/initiators/ > > Documentation/admin-guide/mm/numaperf.rst > > That is the interface that libraries like libmemkind will look at for finding > details w.r.t latency/bandwidth Yes. Only with that, it's still inconvenient to find out which nodes belong to same memory type (has same performance, same topology, managed by same driver, etc). So memory types can still provide useful information even without memory tiering. Best Regards, Huang, Ying