Re: [PATCH v5 3/3] mm/compaction: optimize >0 order folio compaction with free page split.

[Vlastimil Babka]

On 2/14/24 23:04, Zi Yan wrote:
> From: Zi Yan <ziy@xxxxxxxxxx>
> 
> During migration in a memory compaction, free pages are placed in an array
> of page lists based on their order.  But the desired free page order
> (i.e., the order of a source page) might not be always present, thus
> leading to migration failures and premature compaction termination.  Split
> a high order free pages when source migration page has a lower order to
> increase migration successful rate.
> 
> Note: merging free pages when a migration fails and a lower order free
> page is returned via compaction_free() is possible, but there is too much
> work.  Since the free pages are not buddy pages, it is hard to identify
> these free pages using existing PFN-based page merging algorithm.
> 
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Tested-by: Yu Zhao <yuzhao@xxxxxxxxxx>

Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>

Thanks!