| Message ID | 20230912162815.440749-3-zi.yan@sent.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Enable >0 order folio memory compaction | expand |
On 9/13/2023 12:28 AM, 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 868e92e55d27..45747ab5f380 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1801,9 +1801,46 @@ 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_free) { > - isolate_freepages(cc); > + int i; > + > + for (i = order + 1; i <= MAX_ORDER; i++) { > + if (cc->freepages[i].nr_free) { > + 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_free--; > + > + while (start_order > order) { > + start_order--; > + size >>= 1; > + > + list_add(&freepage[size].lru, > + &cc->freepages[start_order].pages); > + cc->freepages[start_order].nr_free++; > + set_page_private(&freepage[size], start_order); IIUC, these split pages should also call functions to initialize? e.g. prep_compound_page()? > + } > + 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_free) > return NULL; > } > @@ -1814,6 +1851,7 @@ 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 dst; > }
On 18 Sep 2023, at 3:34, Baolin Wang wrote: > On 9/13/2023 12:28 AM, 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 868e92e55d27..45747ab5f380 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -1801,9 +1801,46 @@ 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_free) { >> - isolate_freepages(cc); >> + int i; >> + >> + for (i = order + 1; i <= MAX_ORDER; i++) { >> + if (cc->freepages[i].nr_free) { >> + 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_free--; >> + >> + while (start_order > order) { >> + start_order--; >> + size >>= 1; >> + >> + list_add(&freepage[size].lru, >> + &cc->freepages[start_order].pages); >> + cc->freepages[start_order].nr_free++; >> + set_page_private(&freepage[size], start_order); > > IIUC, these split pages should also call functions to initialize? e.g. prep_compound_page()? Not at this place. It is done right below and above "done" label. When free pages are on cc->freepages, we want to keep them without being post_alloc_hook() or prep_compound_page() processed for a possible future split. A free page is only initialized when it is returned by compaction_alloc(). > >> + } >> + 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_free) >> return NULL; >> } >> @@ -1814,6 +1851,7 @@ 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 dst; >> } -- Best Regards, Yan, Zi
On 9/19/2023 1:20 AM, Zi Yan wrote: > On 18 Sep 2023, at 3:34, Baolin Wang wrote: > >> On 9/13/2023 12:28 AM, 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 868e92e55d27..45747ab5f380 100644 >>> --- a/mm/compaction.c >>> +++ b/mm/compaction.c >>> @@ -1801,9 +1801,46 @@ 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_free) { >>> - isolate_freepages(cc); >>> + int i; >>> + >>> + for (i = order + 1; i <= MAX_ORDER; i++) { >>> + if (cc->freepages[i].nr_free) { >>> + 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_free--; >>> + >>> + while (start_order > order) { >>> + start_order--; >>> + size >>= 1; >>> + >>> + list_add(&freepage[size].lru, >>> + &cc->freepages[start_order].pages); >>> + cc->freepages[start_order].nr_free++; >>> + set_page_private(&freepage[size], start_order); >> >> IIUC, these split pages should also call functions to initialize? e.g. prep_compound_page()? > > Not at this place. It is done right below and above "done" label. When free pages > are on cc->freepages, we want to keep them without being post_alloc_hook() or > prep_compound_page() processed for a possible future split. A free page is > only initialized when it is returned by compaction_alloc(). Ah, I see. Thanks for explanation.
diff --git a/mm/compaction.c b/mm/compaction.c index 868e92e55d27..45747ab5f380 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1801,9 +1801,46 @@ 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_free) { - isolate_freepages(cc); + int i; + + for (i = order + 1; i <= MAX_ORDER; i++) { + if (cc->freepages[i].nr_free) { + 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_free--; + + while (start_order > order) { + start_order--; + size >>= 1; + + list_add(&freepage[size].lru, + &cc->freepages[start_order].pages); + cc->freepages[start_order].nr_free++; + 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_free) return NULL; } @@ -1814,6 +1851,7 @@ 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 dst; }