Re: [PATCH] mm/damon: prevent migration fallback to non-target nodes

[SJ Park <sj@kernel.org>]

Hello jzh,

On Wed,  8 Jul 2026 01:07:54 -0700 zjh <jiahuitry@outlook.com> wrote:

> DAMOS_MIGRATE_{HOT,COLD} passes a target NUMA node to migrate_pages().
> But alloc_migration_target() treats mtc->nid as a preferred node unless
> __GFP_THISNODE is set.  Hence target allocation can fall back to another
> node, and migrate_pages() can report success without placing the folio on
> the requested target node.
> 
> Make DAMON migration target allocation strict by setting __GFP_THISNODE.
> This is consistent with alloc_misplaced_dst_folio() and
> alloc_demote_folio(), which also use __GFP_THISNODE for migrations to an
> explicit destination node.

Thank you for sharing this patch.  So this patch is introducing a small
behavioral change.  May I ask why you think the new behavior is better?  Have
you find some negative user impacts from the current behavior?

> 
> Signed-off-by: zjh <jiahuitry@outlook.com>

We as the kernel community disallow [1] anonymous patch submissions.  Is zjh
your preferred identity?  Also, it is not a strict rule, but we as the mm
community prefer using a formal name if that's ok.

[1] https://docs.kernel.org/process/submitting-patches.html#developer-s-certificate-of-origin-1-1


Thanks,
SJ

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