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Wysocki" References: <20220830081736.119281-1-aneesh.kumar@linux.ibm.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> <5aaf395d-514a-2717-58c6-3845b97692bd@linux.ibm.com> <87sfl6y4d0.fsf@yhuang6-desk2.ccr.corp.intel.com> <87ilm2xv26.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Aneesh Kumar K V In-Reply-To: <87ilm2xv26.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset=UTF-8 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ZRcZFwN0Ay3LTVaTl263iqDQHXJUGZm2 X-Proofpoint-ORIG-GUID: E4BerbTdse1hFUo95mgqnFrSAtNMKvOy 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=2022-09-05_04,2022-09-05_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 mlxlogscore=999 impostorscore=0 adultscore=0 clxscore=1015 bulkscore=0 suspectscore=0 malwarescore=0 mlxscore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2207270000 definitions=main-2209050025 ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=nFTtKeM2; spf=pass (imf10.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=1662355700; a=rsa-sha256; cv=none; b=tud7Xb3/lZss4XKjHLR9dLYdWbIsEIPDGM92Pgo1hlPQScTY6UGMD2tAqGs9hYGj+6CBT7 HL2riqkZpIstafYJQkeFYEkjmKBfh+3vkUtboOp6dOP38SJAfAMrW4+RcyjEQy+v9urG9E YHK6gw/hRr+42M9QpgkI0wAq0qJRRIs= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662355700; 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=XstGMMdmk4mA+j3AofY0B9LTpBuMzR8MoBKUzN4BFsY=; b=oNvetpiLqxdUkFdouBVZiiF8dPrt2Ei0b1q3OVqPu1dNIRV6TBAyYUuBQkWQVf+cwiI35r PQtsK5nDh2Bb0VZcRVFeV2B5OjBdEV/3u8TnzKNN8BmAKNkoalNQAdz3dw4MLyp6PkLvF9 V+wfpigxLElsl2l93IVUcH+0uGIFS4k= Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=nFTtKeM2; spf=pass (imf10.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: rspam06 X-Stat-Signature: qnfgwy564di6qfc4meaumgesnt5ame11 X-Rspam-User: X-Rspamd-Queue-Id: BB70FC005D X-HE-Tag: 1662355700-910299 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 9/5/22 10:43 AM, Huang, Ying wrote: > Aneesh Kumar K V writes: > >> On 9/5/22 7:22 AM, Huang, Ying wrote: >>> Aneesh Kumar K V writes: >>> >>>> 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. >>> >>> I just prefer to separate memory_tier and memory_type sysfs directories >>> personally. Because memory_type describes the physical memory types and >>> performance, while memory_tier is more about the policy to group >>> memory_types. >>> >> IMHO we can decide on that based on why we end up adding memory_type details to sysfs. If that >> is only for memory tier modification from userspace we can look at adding that in the memory tiering >> sysfs hierarchy. >> >> Also since we have precedence of consolidating things within a sysfs hierarchy as explained in previous emails, >> I think we should keep "memory_tiering" as sysfs subsystem name? I hope we can get an agreement on that >> for now? > > I prefer to separate memory_tier and memory_type, so the subsystem name > should be "memory_tier". You prefer to consolidate memory_tier and > memory_type, so the subsystem name should be "memory_tiering". > > The main reason behind my idea is that memory_type isn't tied with > memory tiering directly. It describes some hardware property. Even if > we don't use memory tiering, we can still use that to classify the > memory devices in the system. > > Why do you want to consolidate them? To reduce one directory from > sysfs? > So that it is much intuitive for user to got to memory_tiering sysfs hierarchy to change the memory tier levels. As I mentioned earlier the reason for consolidating things is to accommodate the possibility of supporting changing abstract distance of a memory type so that we can change the memory tier assignment of that specific memory type. I don't see any other reason we would want to expose memory type to userspace as of now. > I want to get opinions from other people too. > > Best Regards, > Huang, Ying -aneesh