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 -aneesh
