On Thu, Jan 15, 2026 at 10:20:10AM +0100, David Hildenbrand (Red Hat) wrote:
> Migration support for balloon memory depends on MIGRATION not
> COMPACTION. Compaction is simply another user of page migration.
>
> The last dependency on compaction.c was effectively removed with
> commit 3d388584d599 ("mm: convert "movable" flag in page->mapping to a
> page flag"). Ever since, everything for handling movable_ops page
> migration resides in core migration code.
>
> So let's change the dependency and adjust the description +
> help text.
>
> We'll rename BALLOON_COMPACTION separately next.
>
> Signed-off-by: David Hildenbrand (Red Hat) <[email protected]>Far pithier also. LGTM so: Reviewed-by: Lorenzo Stoakes <[email protected]> > --- > mm/Kconfig | 17 +++++++---------- > 1 file changed, 7 insertions(+), 10 deletions(-) > > diff --git a/mm/Kconfig b/mm/Kconfig > index 24a3ff149a1b0..0d13c1b36e1c1 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -599,17 +599,14 @@ config MEMORY_BALLOON > # > # support for memory balloon compaction > config BALLOON_COMPACTION > - bool "Allow for balloon memory compaction/migration" > + bool "Allow for balloon memory migration" > default y > - depends on COMPACTION && MEMORY_BALLOON > - help > - Memory fragmentation introduced by ballooning might reduce > - significantly the number of 2MB contiguous memory blocks that can be > - used within a guest, thus imposing performance penalties associated > - with the reduced number of transparent huge pages that could be used > - by the guest workload. Allowing the compaction & migration for memory > - pages enlisted as being part of memory balloon devices avoids the > - scenario aforementioned and helps improving memory defragmentation. > + depends on MIGRATION && MEMORY_BALLOON > + help > + Allow for migration of pages inflated in a memory balloon such that > + they can be allocated from memory areas only available for movable > + allocations (e.g., ZONE_MOVABLE, CMA) and such that they can be > + migrated for memory defragmentation purposes by memory compaction. > > # > # support for memory compaction > -- > 2.52.0 >
