| Message ID | 20231113170157.280181-4-zi.yan@sent.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Enable >0 order folio memory compaction | expand |
On 13/11/2023 17:01, Zi Yan wrote: > From: Zi Yan <ziy@nvidia.com> > > 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. 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@nvidia.com> > --- > mm/compaction.c | 40 +++++++++++++++++++++++++++++++++++++++- > 1 file changed, 39 insertions(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index ec6b5cc7e907..9c083e6b399a 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1806,9 +1806,46 @@ 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; > > +again: > if (!cc->freepages[order].nr_pages) { > - isolate_freepages(cc); > + int i; > + > + for (i = order + 1; i <= MAX_ORDER; i++) { > + if (cc->freepages[i].nr_pages) { > + struct page *freepage = > + list_first_entry(&cc->freepages[i].pages, > + struct page, lru); > + > + int start_order = i; > + unsigned long size = 1 << start_order; > + > + list_del(&freepage->lru); > + cc->freepages[i].nr_pages--; > + > + while (start_order > order) { > + start_order--; > + size >>= 1; > + > + list_add(&freepage[size].lru, > + &cc->freepages[start_order].pages); > + cc->freepages[start_order].nr_pages++; > + set_page_private(&freepage[size], start_order); > + } > + post_alloc_hook(freepage, order, __GFP_MOVABLE); > + if (order) > + prep_compound_page(freepage, order); > + dst = page_folio(freepage); > + goto done; Perhaps just do: dst = (struct folio *)freepage; goto done; then move done: up a couple of statements below, so that post_alloc_hook() and prep_compound_page() are always done below in common path? Although perhaps the cast is frowned upon, you're already making the assumption that page and folio are interchangable the way you call list_first_entry(). > + } > + } > + if (!has_isolated_pages) { > + isolate_freepages(cc); > + has_isolated_pages = true; > + goto again; > + } > + > if (!cc->freepages[order].nr_pages) > return NULL; > } > @@ -1819,6 +1856,7 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data) > post_alloc_hook(&dst->page, order, __GFP_MOVABLE); > if (order) > prep_compound_page(&dst->page, order); > +done: > cc->nr_freepages -= 1 << order; > return page_rmappable_folio(&dst->page); > }
On 22 Nov 2023, at 5:26, Ryan Roberts wrote: > On 13/11/2023 17:01, Zi Yan wrote: >> From: Zi Yan <ziy@nvidia.com> >> >> 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. 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@nvidia.com> >> --- >> mm/compaction.c | 40 +++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 39 insertions(+), 1 deletion(-) >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index ec6b5cc7e907..9c083e6b399a 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -1806,9 +1806,46 @@ 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; >> >> +again: >> if (!cc->freepages[order].nr_pages) { >> - isolate_freepages(cc); >> + int i; >> + >> + for (i = order + 1; i <= MAX_ORDER; i++) { >> + if (cc->freepages[i].nr_pages) { >> + struct page *freepage = >> + list_first_entry(&cc->freepages[i].pages, >> + struct page, lru); >> + >> + int start_order = i; >> + unsigned long size = 1 << start_order; >> + >> + list_del(&freepage->lru); >> + cc->freepages[i].nr_pages--; >> + >> + while (start_order > order) { >> + start_order--; >> + size >>= 1; >> + >> + list_add(&freepage[size].lru, >> + &cc->freepages[start_order].pages); >> + cc->freepages[start_order].nr_pages++; >> + set_page_private(&freepage[size], start_order); >> + } >> + post_alloc_hook(freepage, order, __GFP_MOVABLE); >> + if (order) >> + prep_compound_page(freepage, order); >> + dst = page_folio(freepage); >> + goto done; > > Perhaps just do: > > dst = (struct folio *)freepage; > goto done; > > then move done: up a couple of statements below, so that post_alloc_hook() and > prep_compound_page() are always done below in common path? Although perhaps the Sure. Thanks for the suggestion. > cast is frowned upon, you're already making the assumption that page and folio > are interchangable the way you call list_first_entry(). To save the _compound_head() in page_folio()? OK. > >> + } >> + } >> + if (!has_isolated_pages) { >> + isolate_freepages(cc); >> + has_isolated_pages = true; >> + goto again; >> + } >> + >> if (!cc->freepages[order].nr_pages) >> return NULL; >> } >> @@ -1819,6 +1856,7 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data) >> post_alloc_hook(&dst->page, order, __GFP_MOVABLE); >> if (order) >> prep_compound_page(&dst->page, order); >> +done: >> cc->nr_freepages -= 1 << order; >> return page_rmappable_folio(&dst->page); >> } -- Best Regards, Yan, Zi
diff --git a/mm/compaction.c b/mm/compaction.c index ec6b5cc7e907..9c083e6b399a 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1806,9 +1806,46 @@ 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; +again: if (!cc->freepages[order].nr_pages) { - isolate_freepages(cc); + int i; + + for (i = order + 1; i <= MAX_ORDER; i++) { + if (cc->freepages[i].nr_pages) { + struct page *freepage = + list_first_entry(&cc->freepages[i].pages, + struct page, lru); + + int start_order = i; + unsigned long size = 1 << start_order; + + list_del(&freepage->lru); + cc->freepages[i].nr_pages--; + + while (start_order > order) { + start_order--; + size >>= 1; + + list_add(&freepage[size].lru, + &cc->freepages[start_order].pages); + cc->freepages[start_order].nr_pages++; + set_page_private(&freepage[size], start_order); + } + post_alloc_hook(freepage, order, __GFP_MOVABLE); + if (order) + prep_compound_page(freepage, order); + dst = page_folio(freepage); + goto done; + } + } + if (!has_isolated_pages) { + isolate_freepages(cc); + has_isolated_pages = true; + goto again; + } + if (!cc->freepages[order].nr_pages) return NULL; } @@ -1819,6 +1856,7 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data) post_alloc_hook(&dst->page, order, __GFP_MOVABLE); if (order) prep_compound_page(&dst->page, order); +done: cc->nr_freepages -= 1 << order; return page_rmappable_folio(&dst->page); }