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

[David Hildenbrand <david@redhat.com>]

On 20.02.24 10:03, David Hildenbrand wrote:
> On 16.02.24 18:04, Zi Yan wrote:
>> From: Zi Yan <ziy@nvidia.com>
>>
>> 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@nvidia.com>
>> Suggested-by: Huang Ying <ying.huang@intel.com>
>> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Tested-by: Yu Zhao <yuzhao@google.com>
>> Cc: Adam Manzanares <a.manzanares@samsung.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Kemeng Shi <shikemeng@huaweicloud.com>
>> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> Cc: Luis Chamberlain <mcgrof@kernel.org>
>> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
>> Cc: Mel Gorman <mgorman@techsingularity.net>
>> Cc: Ryan Roberts <ryan.roberts@arm.com>
>> Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Yin Fengwei <fengwei.yin@intel.com>
>> ---
>>    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