Re: [PATCH v2 0/2] mm: refactor zonelist constructors and iterators

[Zenghui Yu]

On 9/12/26 11:04 AM, Gregory Price wrote:
> find_next_best_node() picks the next-closest node when building a
> fallback list, and hardcodes N_MEMORY as the set it picks from.
> 
> Refactor it into find_next_best_node_in(), which takes the candidate
> set explicitly.
> 
> This makes the existing behaviour explicit at both mm/memory-tiers.c
> call sites - they select demotion targets in fallback order from
> N_MEMORY - and lets callers narrow that set.
> 
> Then extract the per-node construction loop out of build_zonelists()
> into build_node_zonelist(),i parameterised on the candidate nodemask
> and destination zonelist index.
> 
> Together these allow a zonelist to be built over a candidate set other
> than N_MEMORY, into a zonelist other than FALLBACK, and iterated in
> fallback order over a caller-defined subset.
> 
> These are prerequisites for generating a private node zonelist (nodes
> unreachable by default), but are otherwise general improvements to
> the existing interfaces so I'm proposing them separately.
> 
> No functional change intended - purely refactor commits.
> 
> Verified on x86_64:
> 
>   - find_next_best_node_in() compiles to the same 319 bytes as
>     find_next_best_node().
>   - Both mm/memory-tiers.c callers grow a single instruction - the
>     added argument.
>   - Boot-time fallback orders are identical on a 4-node guest with an
>     asymmetric distance matrix.
> 
> Gregory Price (2):
>   mm: refactor find_next_best_node to find_next_best_node_in
>   mm/page_alloc: refactor build_node_zonelist() out of build_zonelists()
> 
>  mm/internal.h     |  6 ++--
>  mm/memory-tiers.c |  7 +++--
>  mm/page_alloc.c   | 74 +++++++++++++++++++----------------------------
>  3 files changed, 38 insertions(+), 49 deletions(-)

Reviewed-by: Zenghui Yu (Huawei) <zenghui.yu@xxxxxxxxx>

Thanks,
Zenghui