Messages in this thread | | | Date | Wed, 8 Jun 2022 21:45:43 +0530 | Subject | Re: [PATCH v5 2/9] mm/demotion: Expose per node memory tier to sysfs | From | Aneesh Kumar K V <> |
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On 6/8/22 9:36 PM, Tim Chen wrote: > On Wed, 2022-06-08 at 10:25 +0530, Aneesh Kumar K V wrote: >> On 6/8/22 1:45 AM, Tim Chen wrote: >>> On Fri, 2022-06-03 at 19:12 +0530, Aneesh Kumar K.V wrote: >>>> >>>> +static struct memory_tier *__node_get_memory_tier(int node) >>>> +{ >>>> + struct memory_tier *memtier; >>>> + >>>> + list_for_each_entry(memtier, &memory_tiers, list) { >>> >>> We could need to map node to mem_tier quite often, if we need >>> to account memory usage at tier level. It will be more efficient >>> to have a pointer from node (pgdat) to memtier rather >>> than doing a search through the list. >>> >>> >> >> That is something I was actively trying to avoid. Currently all struct >> memory_tier references are with memory_tier_lock mutex held. That >> simplify the locking and reference counting. >> >> As of now we are able to implement all the required interfaces without >> pgdat having pointers to struct memory_tier. We can update pgdat with >> memtier details when we are implementing changes requiring those. We >> could keep additional memtier->dev reference to make sure memory tiers >> are not destroyed while other part of the kernel is referencing the >> same. But IMHO such changes should wait till we have users for the same. >> > > I think we should have an efficient mapping from node to memtier from > the get go. There are many easily envisioned scenarios where > we need to map from node to memtier, which Ying pointed out. >
I did an initial implementation here. We need to make sure we can access NODE_DATA()->memtier lockless. Can you review the changes here
https://lore.kernel.org/linux-mm/87sfoffcfz.fsf@linux.ibm.com
-aneesh
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