Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> writes: > On 9/2/22 2:34 PM, Huang, Ying wrote: >> Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> writes: >> >>> On 9/2/22 1:27 PM, Huang, Ying wrote: >>>> Wei Xu <weixugc@xxxxxxxxxx> writes: >>>> >>>>> On Thu, Sep 1, 2022 at 11:44 PM Aneesh Kumar K V >>>>> <aneesh.kumar@xxxxxxxxxxxxx> wrote: >>>>>> >>>>>> On 9/2/22 12:10 PM, Huang, Ying wrote: >>>>>>> Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> writes: >>>>>>> >>>>>>>> On 9/2/22 11:42 AM, Huang, Ying wrote: >>>>>>>>> Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> writes: >>>>>>>>> >>>>>>>>>> On 9/2/22 11:10 AM, Huang, Ying wrote: >>>>>>>>>>> Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> writes: >>>>>>>>>>> >>>>>>>>>>>> On 9/2/22 10:39 AM, Wei Xu wrote: >>>>>>>>>>>>> On Thu, Sep 1, 2022 at 5:33 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>> Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> writes: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> On 9/1/22 12:31 PM, Huang, Ying wrote: >>>>>>>>>>>>>>>> "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx >>>>>>>>>>> >>>>>>>>>>> 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. > 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. As above, because I think memory_type can provide value even outside of memory_tier, I prefer to add memory_type sysfs interface anyway personally. Best Regards, Huang, Ying
