On 12 Feb 2024, at 13:27, Yu Zhao wrote:
> On Mon, Feb 12, 2024 at 9:35 AM Zi Yan <zi.yan@xxxxxxxx> 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>
>> Cc: Adam Manzanares <a.manzanares@xxxxxxxxxxx>
>> Cc: David Hildenbrand <david@xxxxxxxxxx>
>> Cc: Huang Ying <ying.huang@xxxxxxxxx>
>> 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>
>> Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
>> ---
>> mm/compaction.c | 36 +++++++++++++++++++++++++++++++-----
>> 1 file changed, 31 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index d0a05a621b67..25908e36b97c 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -1832,15 +1832,41 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
>> struct compact_control *cc = (struct compact_control *)data;
>> struct folio *dst;
>> int order = folio_order(src);
>> + bool has_isolated_pages = false;
>> + int start_order;
>> + struct page *freepage;
>> + unsigned long size;
>> +
>> +again:
>> + for (start_order = order; start_order < NR_PAGE_ORDERS; start_order++)
>> + if (!list_empty(&cc->freepages[start_order]))
>> + break;
>>
>> - if (list_empty(&cc->freepages[order])) {
>> - isolate_freepages(cc);
>> - if (list_empty(&cc->freepages[order]))
>> + /* no free pages in the list */
>> + if (start_order == NR_PAGE_ORDERS) {
>> + if (!has_isolated_pages) {
>> + isolate_freepages(cc);
>> + has_isolated_pages = true;
>> + goto again;
>> + } else
>> return NULL;
>
> Nit: remove the "else" above, or just:
>
> if (has_isolated_pages)
> return NULL;
> isolate_freepages(cc);
> has_isolated_pages = true;
> goto again;
Will do. Thanks.
--
Best Regards,
Yan, Zi
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