Messages in this thread | | | Date | Wed, 8 Jun 2022 13:59:54 +0530 | Subject | Re: [PATCH v5 6/9] mm/demotion: Add support for removing node from demotion memory tiers | From | Aneesh Kumar K V <> |
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On 6/8/22 1:53 PM, Ying Huang wrote: > On Wed, 2022-06-08 at 13:50 +0530, Aneesh Kumar K V wrote: >> On 6/8/22 12:29 PM, Ying Huang wrote: >>> On Fri, 2022-06-03 at 19:12 +0530, Aneesh Kumar K.V wrote: >>>> This patch adds the special string "none" as a supported memtier value >>>> that we can use to remove a specific node from being using as demotion target. >>>> >>>> For ex: >>>> :/sys/devices/system/node/node1# cat memtier >>>> 1 >>>> :/sys/devices/system/node/node1# cat ../../memtier/memtier1/nodelist >>>> 1-3 >>>> :/sys/devices/system/node/node1# echo none > memtier >>>> :/sys/devices/system/node/node1# >>>> :/sys/devices/system/node/node1# cat memtier >>>> :/sys/devices/system/node/node1# cat ../../memtier/memtier1/nodelist >>>> 2-3 >>>> :/sys/devices/system/node/node1# >>> >>> Do you have a practical use case for this? What kind of memory node >>> needs to be removed from memory tiers demotion/promotion? >>> >> >> This came up in our internal discussion. It was mentioned that there is >> a need to skip some slow memory nodes from participating in demotion. > > Again, can you provide a practical use case? Why we shouldn't demote > cold pages to these slow memory nodes? How do we use these slow memory > node? These slow memory node is slower than disk? >
This was discussed in the context of memory borrowed from remote machine (aka OpenCAPI memory). In such case, we would have a memory only NUMA node which we want to avoid using for demotion.
-aneesh
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