Re: [RFC PATCH v2 0/4] mm: compaction: mTHP-friendly memory compaction

[Vlastimil Babka (SUSE)]

On 10/1/26 02:14, Bo Zhang wrote:
> Open questions:
> 
> 1. In skip_isolation_on_order() and elsewhere, the target order is read
>    from huge_anon_orders_always directly, since during proactive
>    compaction cc->order is -1 (via compact_memory) and there is no clean
>    way to plumb the mTHP order down.

Isn't using  struct compact_control clean enough? There's already many
fields like
    bool direct_compaction;         /* False from kcompactd or /proc/... */
    bool proactive_compaction;      /* kcompactd proactive compaction */

Who says is_via_compact_memory() cannot be refactored into something using
these kinds of fields and not 'order' being -1, which could be then used as
the target order.

> This variable can change under
>    userspace at any time, making the semantics fragile. Ideas on how to
>    pass the target order through the proactive path cleanly are welcome.
>