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Wysocki" 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> <87wnamxi30.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Aneesh Kumar K V In-Reply-To: <87wnamxi30.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset=UTF-8 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ZfX0-LowShHPJLjikCQJmx_d2Dkg0j6M X-Proofpoint-ORIG-GUID: Tshqiy_QkK55o91ca1MWM24NLLIaypB1 Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-09-02_01,2022-08-31_03,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 bulkscore=0 suspectscore=0 priorityscore=1501 mlxlogscore=999 clxscore=1015 spamscore=0 impostorscore=0 mlxscore=0 phishscore=0 lowpriorityscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2207270000 definitions=main-2209020045 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662111888; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=OHrCdqR+7nVowticktGiwfekN4OfMW/k6KwPMJ/DUGA=; b=XOrA0XsXBWUd3ktr6k6u9mj5nmahhHo21H52RCtAB66bCHP5xxFTp6wtnqCSBqj1pfohAa s7OOqzXMIZUDHzv0HxyqrGsyp53IeW9iRmKUtmGMOIDRMXSD1cD+KJYrh17zctyFLshXI4 V8dg2u8Clfbd+GPghV95x2wZhUMBLH0= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=Ao3hDPfZ; spf=pass (imf23.hostedemail.com: domain of aneesh.kumar@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=aneesh.kumar@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662111888; a=rsa-sha256; cv=none; b=cNN2aJdGGq1hMBlquFHmAfp/0CZkk6ydvSL1I/7YlRgsZsi/4B3exB9zIzs2X9YuqtDnbK YV/I4sQq6pBv34PLczas/8DS1NN1nwaoo7V59kZxIfhGWJQj9oyO+r/R79oiA9BVaNW0Nw Kk6rVVG8BdoSn2j24MRU12aIew/49vM= Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=Ao3hDPfZ; spf=pass (imf23.hostedemail.com: domain of aneesh.kumar@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=aneesh.kumar@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Rspamd-Server: rspam11 X-Stat-Signature: z3jrncryt5fr5ryr96ebn95cfc67893z X-Rspamd-Queue-Id: 55B58140060 X-Rspam-User: X-HE-Tag: 1662111888-942528 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 9/2/22 2:34 PM, Huang, Ying wrote: > 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. > I am not sure i quiet follow what to conclude from your reply. I used the subsystem name "memory_tiering" so that all memory tiering related information can be consolidated there. I guess you agreed to the above part that we can consolidated things like that. We might end up adding memory_type there if we allow changing "abstract distance" of a memory type from userspace later. Otherwise, I don't see a reason for memory type to be exposed. But then we don't have to decide on this now. -aneesh