On 22 Jan 2024, at 22:46, Zi Yan wrote: > From: Zi Yan <ziy@xxxxxxxxxx> > > Before last commit, memory compaction only migrates order-0 folios and > skips >0 order folios. Last commit splits all >0 order folios during > compaction. This commit migrates >0 order folios during compaction by > keeping isolated free pages at their original size without splitting them > into order-0 pages and using them directly during migration process. > > What is different from the prior implementation: > 1. All isolated free pages are kept in a NR_PAGE_ORDERS array of page > lists, where each page list stores free pages in the same order. > 2. All free pages are not post_alloc_hook() processed nor buddy pages, > although their orders are stored in first page's private like buddy > pages. > 3. During migration, in new page allocation time (i.e., in > compaction_alloc()), free pages are then processed by post_alloc_hook(). > When migration fails and a new page is returned (i.e., in > compaction_free()), free pages are restored by reversing the > post_alloc_hook() operations using newly added > free_pages_prepare_fpi_none(). > > Step 3 is done for a latter optimization that splitting and/or merging free > pages during compaction becomes easier. > > Note: without splitting free pages, compaction can end prematurely due to > migration will return -ENOMEM even if there is free pages. This happens > when no order-0 free page exist and compaction_alloc() return NULL. > > Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> > --- > mm/compaction.c | 148 +++++++++++++++++++++++++++++------------------- > mm/internal.h | 9 ++- > mm/page_alloc.c | 6 ++ > 3 files changed, 103 insertions(+), 60 deletions(-) > <snip> > @@ -1462,7 +1489,7 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn) > if (!page) > return; > > - isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); > + isolate_freepages_block(cc, &start_pfn, end_pfn, cc->freepages, 1, false); > > /* Skip this pageblock in the future as it's full or nearly full */ > if (start_pfn == end_pfn && !cc->no_set_skip_hint) > @@ -1591,7 +1618,7 @@ static void fast_isolate_freepages(struct compact_control *cc) > nr_scanned += nr_isolated - 1; > total_isolated += nr_isolated; > cc->nr_freepages += nr_isolated; > - list_add_tail(&page->lru, &cc->freepages); > + list_add_tail(&page->lru, &cc->freepages[order].pages); I did not increase nr_pages here, so compaction_alloc() thought no free page was isolated. This is the fix: diff --git a/mm/compaction.c b/mm/compaction.c index 335a6f6787e4..fa9993c8a389 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1638,6 +1638,7 @@ static void fast_isolate_freepages(struct compact_control *cc) total_isolated += nr_isolated; cc->nr_freepages += nr_isolated; list_add_tail(&page->lru, &cc->freepages[order].pages); + cc->freepages[order].nr_pages++; count_compact_events(COMPACTISOLATED, nr_isolated); } else { /* If isolation fails, abort the search */ I will send out v3 once I rerun vm-scalability and thpcompact. -- Best Regards, Yan, Zi
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