Re: [PATCH v6 2/4] mm/compaction: enable compacting >0 order folios.

[David Hildenbrand]

On 20.02.24 10:03, David Hildenbrand wrote:
> On 16.02.24 18:04, Zi Yan wrote:
> > From: Zi Yan <ziy@xxxxxxxxxx>
> >
> > migrate_pages() supports >0 order folio migration and during compaction,
> > even if compaction_alloc() cannot provide >0 order free pages,
> > migrate_pages() can split the source page and try to migrate the base
> > pages from the split.  It can be a baseline and start point for adding
> > support for compacting >0 order folios.
> >
> > Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> > Suggested-by: Huang Ying <ying.huang@xxxxxxxxx>
> > Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> > Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Tested-by: Yu Zhao <yuzhao@xxxxxxxxxx>
> > Cc: Adam Manzanares <a.manzanares@xxxxxxxxxxx>
> > Cc: David Hildenbrand <david@xxxxxxxxxx>
> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> > Cc: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
> > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> > Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> > Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> > Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
> > Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
> > Cc: Vlastimil Babka <vbabka@xxxxxxx>
> > Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
> > ---
> >    mm/compaction.c | 66 ++++++++++++++++++++++++++++++++++++++-----------
> >    1 file changed, 52 insertions(+), 14 deletions(-)
> >
> > diff --git a/mm/compaction.c b/mm/compaction.c
> > index cc801ce099b4..aa6aad805c4d 100644
> > --- a/mm/compaction.c
> > +++ b/mm/compaction.c
> > @@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
> >    	return too_many;
> >    }
> >    
> > +/*
>
>
> Can't you add these comments to the respective checks? Like
>
> static bool skip_isolation_on_order(int order, int target_order)
> {
> 	/*
> 	 * Unless we are performing global compaction (targert_order <
> 	 * 0), skip any folios that are larger than the target order: we
> 	 * wouldn't be here if we'd have a free folio with the desired
> 	 * target_order, so migrating this folio would likely fail
> 	 * later.
> 	 */
> 	if (target_order != -1 && order >= target_order)
> 		return true;

I just stumbled over "is_via_compact_memory", likely that should be used 
instead of the "!= -1 check.

--
Cheers,

David / dhildenb