On Wed, 25 May 2022 10:27:42 -0700 Wei Xu <weixugc@xxxxxxxxxx> wrote: > On Wed, May 25, 2022 at 3:01 AM Aneesh Kumar K V > <aneesh.kumar@xxxxxxxxxxxxx> wrote: > > > > On 5/25/22 2:33 PM, Ying Huang wrote: > > > On Tue, 2022-05-24 at 22:32 -0700, Wei Xu wrote: > > >> On Tue, May 24, 2022 at 1:24 AM Ying Huang <ying.huang@xxxxxxxxx> wrote: > > >>> > > >>> On Tue, 2022-05-24 at 00:04 -0700, Wei Xu wrote: > > >>>> On Thu, May 19, 2022 at 8:06 PM Ying Huang <ying.huang@xxxxxxxxx> wrote: > > >>>>> > > > > ... > > > > > > > > OK. Just to confirm. Does this mean that we will have fixed device ID, > > > for example, > > > > > > GPU memtier255 > > > DRAM (with CPU) memtier0 > > > PMEM memtier1 > > > > > > When we add a new memtier, it can be memtier254, or memter2? The rank > > > value will determine the real demotion order. > > > > > > I think you may need to send v3 to make sure everyone is at the same > > > page. > > > > > > > What we have implemented which we will send as RFC shortly is below. > > > > cd /sys/dekvaneesh@ubuntu-guest:~$ cd /sys/devices/system/ > > kvaneesh@ubuntu-guest:/sys/devices/system$ pwd > > /sys/devices/system > > kvaneesh@ubuntu-guest:/sys/devices/system$ ls > > clockevents clocksource container cpu edac memory memtier mpic > > node power > > kvaneesh@ubuntu-guest:/sys/devices/system$ cd memtier/ > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier$ pwd > > /sys/devices/system/memtier > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier$ ls > > default_rank max_rank memtier1 power uevent > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier$ cat default_rank > > 1 > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier$ cat max_rank > > 3 > > For flexibility, we don't want max_rank to be interpreted as the > number of memory tiers. Also, we want to leave spaces in rank values > to allow new memtiers to be inserted when needed. So I'd suggest to > make max_rank a much larger value (e.g. 255). > > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier$ cd memtier1/ > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier/memtier1$ ls > > nodelist power rank subsystem uevent > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier/memtier1$ cat nodelist > > 0-3 > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier/memtier1$ cat rank > > 1 > > kvaneesh@ubuntu-guest:/sys/devices/system/memtier/memtier1$ cd > > ../../node/node1/ > > kvaneesh@ubuntu-guest:/sys/devices/system/node/node1$ cat memtier > > 1 > > kvaneesh@ubuntu-guest:/sys/devices/system/node/node1$ > > root@ubuntu-guest:/sys/devices/system/node/node1# echo 0 > memtier > > root@ubuntu-guest:/sys/devices/system/node/node1# cat memtier > > 0 > > root@ubuntu-guest:/sys/devices/system/node/node1# cd ../../memtier/ > > root@ubuntu-guest:/sys/devices/system/memtier# ls > > default_rank max_rank memtier0 memtier1 power uevent > > root@ubuntu-guest:/sys/devices/system/memtier# cd memtier0/ > > root@ubuntu-guest:/sys/devices/system/memtier/memtier0# cat nodelist > > 1 > > root@ubuntu-guest:/sys/devices/system/memtier/memtier0# cat rank > > 0 > > It looks like the example here demonstrates the dynamic creation of > memtier0. If so, how is the rank of memtier0 determined? If we want > to support creating new memtiers at runtime, I think an explicit > interface that specifies both device ID and rank is preferred to avoid > implicit dependencies between device IDs and ranks. Why make device ID explicit - it's meaningless I think? How about a creation interface that is simply writing the rank value to create a new one? The only race I can see would be to get two parallel attempts to create a new tier with the same rank. That seems unlikely to matter unless we support changing rank later. Two attempts to create the same device ID tier seems more likely to cause fiddly races. Jonathan > > > root@ubuntu-guest:/sys/devices/system/memtier/memtier0# echo 4 > rank > > bash: rank: Permission denied > > root@ubuntu-guest:/sys/devices/system/memtier/memtier0#
