On 5/27/22 7:45 PM, Jonathan Cameron wrote:
On Fri, 27 May 2022 17:55:23 +0530
"Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> wrote:
From: Jagdish Gediya <jvgediya@xxxxxxxxxxxxx>
Add support to read/write the memory tierindex for a NUMA node.
/sys/devices/system/node/nodeN/memtier
where N = node id
When read, It list the memory tier that the node belongs to.
When written, the kernel moves the node into the specified
memory tier, the tier assignment of all other nodes are not
affected.
If the memory tier does not exist, writing to the above file
create the tier and assign the NUMA node to that tier.
creates
There was some discussion in v2 of Wei Xu's RFC that what matter
for creation is the rank, not the tier number.
My suggestion is move to an explicit creation file such as
memtier/create_tier_from_rank
to which writing the rank gives results in a new tier
with the next device ID and requested rank.
I think the below workflow is much simpler.
:/sys/devices/system# cat memtier/memtier1/nodelist
1-3
:/sys/devices/system# cat node/node1/memtier
1
:/sys/devices/system# ls memtier/memtier*
nodelist power rank subsystem uevent
/sys/devices/system# ls memtier/
default_rank max_tier memtier1 power uevent
:/sys/devices/system# echo 2 > node/node1/memtier
:/sys/devices/system#
:/sys/devices/system# ls memtier/
default_rank max_tier memtier1 memtier2 power uevent
:/sys/devices/system# cat memtier/memtier1/nodelist
2-3
:/sys/devices/system# cat memtier/memtier2/nodelist
1
:/sys/devices/system#
ie, to create a tier we just write the tier id/tier index to
node/nodeN/memtier file. That will create a new memory tier if needed
and add the node to that specific memory tier. Since for now we are
having 1:1 mapping between tier index to rank value, we can derive the
rank value from the memory tier index.
For dynamic memory tier support, we can assign a rank value such that
new memory tiers are always created such that it comes last in the
demotion order.
-aneesh
