Message-ID: <fe0e9434-0c6d-4a24-b209-d40c7b9e9352@redhat.com>
Date: Mon, 16 Jun 2025 16:32:32 +0200
From: David Hildenbrand <david@...hat.com>
To: Oscar Salvador <osalvador@...e.de>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Harry Yoo <harry.yoo@...cle.com>, Rakie Kim <rakie.kim@...com>,
 Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 00/11] Implement numa node notifier

On 16.06.25 15:51, Oscar Salvador wrote:
>   v6 -> v7:
>     - Split previous patch#10 in two, one for page_ext
>       and the other to drop status_change_nid (per David)
>     - Implement feedback on simplifying previous cancel_on_*
>       notifiers and better document the fact that we consumers
>       can get called on _CANCEL_* actions before having been called
>       for previous actions (per David)
>     - Add Acks-by
> 
>   v5 -> v6:
>     - Remove redundant checks (per David)
>     - Fix build failure
>     - Drop 'nid' parameter from memory notify (Per David)
>     - Add RB/ACKs-by
> 
>   v4 -> v5:
>     - Split out conversion for different consumers (per David)
>     - Renamed node-notifier actions (per David)
>     - Added new Documentation for new node-notifier and updated
>       the memory-notifier one to reflect the changes
>     - Make sure we do not trigger anything when !CONFIG_NUMA (per David)
> 
>   v3 -> v4:
>     - Fix typos pointed out by Alok Tiwari
>     - Further cleanups suggested by Vlastimil
>     - Add RBs-by from Vlastimil
> 
>   v2 -> v3:
>     - Add Suggested-by (David)
>     - Replace last N_NORMAL_MEMORY mention in slub (David)
>     - Replace the notifier for autoweitght-mempolicy
>     - Fix build on !CONFIG_MEMORY_HOTPLUG
>   
>   v1 -> v2:
>     - Remove status_change_nid_normal and the code that
>       deals with it (David & Vlastimil)
>     - Remove slab_mem_offline_callback (David & Vlastimil)
>     - Change the order of canceling the notifiers
>       in {online,offline}_pages (Vlastimil)
>     - Fix up a couple of whitespaces (Jonathan Cameron)
>     - Add RBs-by
> 
> Memory notifier is a tool that allow consumers to get notified whenever
> memory gets onlined or offlined in the system.
> Currently, there are 10 consumers of that, but 5 out of those 10 consumers
> are only interested in getting notifications when a numa node changes its
> memory state.
> That means going from memoryless to memory-aware of vice versa.
> 
> Which means that for every {online,offline}_pages operation they get
> notified even though the numa node might not have changed its state.
> This is suboptimal, and we want to decouple numa node state changes from
> memory state changes.
> 
> While we are doing this, remove status_change_nid_normal, as the only
> current user (slub) does not really need it.
> This allows us to further simplify and clean up the code.
> 
> The first patch gets rid of status_change_nid_normal in slub.
> The second patch implements a numa node notifier that does just that, and have
> those consumers register in there, so they get notified only when they are
> interested.
> 
> The third patch replaces 'status_change_nid{_normal}' fields within
> memory_notify with a 'nid', as that is only what we need for memory
> notifer and update the only user of it (page_ext).
> 
> Consumers that are only interested in numa node states change are:
> 
>   - memory-tier
>   - slub
>   - cpuset
>   - hmat
>   - cxl
>   - autoweight-mempolicy
> 


All looking good to me (and much easier to digest now that it's properly 
split up into patches!) :)

-- 
Cheers,

David / dhildenb

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