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mm/compaction: optimize >0 order folio compaction with free page split.
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. Link: https://lkml.kernel.org/r/20240220183220.1451315-5-zi.yan@sent.com Signed-off-by: Zi Yan <ziy@nvidia.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: Huang Ying <ying.huang@intel.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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -1856,15 +1856,40 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
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struct compact_control *cc = (struct compact_control *)data;
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struct folio *dst;
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int order = folio_order(src);
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bool has_isolated_pages = false;
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int start_order;
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struct page *freepage;
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unsigned long size;
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if (list_empty(&cc->freepages[order])) {
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isolate_freepages(cc);
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if (list_empty(&cc->freepages[order]))
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again:
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for (start_order = order; start_order < NR_PAGE_ORDERS; start_order++)
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if (!list_empty(&cc->freepages[start_order]))
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break;
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/* no free pages in the list */
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if (start_order == NR_PAGE_ORDERS) {
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if (has_isolated_pages)
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return NULL;
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isolate_freepages(cc);
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has_isolated_pages = true;
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goto again;
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}
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dst = list_first_entry(&cc->freepages[order], struct folio, lru);
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list_del(&dst->lru);
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freepage = list_first_entry(&cc->freepages[start_order], struct page,
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lru);
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size = 1 << start_order;
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list_del(&freepage->lru);
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while (start_order > order) {
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start_order--;
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size >>= 1;
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list_add(&freepage[size].lru, &cc->freepages[start_order]);
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set_page_private(&freepage[size], start_order);
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}
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dst = (struct folio *)freepage;
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post_alloc_hook(&dst->page, order, __GFP_MOVABLE);
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if (order)
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prep_compound_page(&dst->page, order);
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