From: David Hildenbrand david@redhat.com
mainline inclusion from mainline-v6.9-rc1 commit d7f861b9c43aadbe384ab1382d2e76750bedc91e category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9CHB4 CVE: NA
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Add __tlb_remove_folio_pages(), which will remove multiple consecutive pages that belong to the same large folio, instead of only a single page. We'll be using this function when optimizing unmapping/zapping of large folios that are mapped by PTEs.
We're using the remaining spare bit in an encoded_page to indicate that the next enoced page in an array contains actually shifted "nr_pages". Teach swap/freeing code about putting multiple folio references, and delayed rmap handling to remove page ranges of a folio.
This extension allows for still gathering almost as many small folios as we used to (-1, because we have to prepare for a possibly bigger next entry), but still allows for gathering consecutive pages that belong to the same large folio.
Note that we don't pass the folio pointer, because it is not required for now. Further, we don't support page_size != PAGE_SIZE, it won't be required for simple PTE batching.
We have to provide a separate s390 implementation, but it's fairly straight forward.
Another, more invasive and likely more expensive, approach would be to use folio+range or a PFN range instead of page+nr_pages. But, we should do that consistently for the whole mmu_gather. For now, let's keep it simple and add "nr_pages" only.
Note that it is now possible to gather significantly more pages: In the past, we were able to gather ~10000 pages, now we can also gather ~5000 folio fragments that span multiple pages. A folio fragment on x86-64 can span up to 512 pages (2 MiB THP) and on arm64 with 64k in theory 8192 pages (512 MiB THP). Gathering more memory is not considered something we should worry about, especially because these are already corner cases.
While we can gather more total memory, we won't free more folio fragments. As long as page freeing time primarily only depends on the number of involved folios, there is no effective change for !preempt configurations. However, we'll adjust tlb_batch_pages_flush() separately to handle corner cases where page freeing time grows proportionally with the actual memory size.
Link: https://lkml.kernel.org/r/20240214204435.167852-9-david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Ryan Roberts ryan.roberts@arm.com Cc: Alexander Gordeev agordeev@linux.ibm.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Cc: Arnd Bergmann arnd@arndb.de Cc: Catalin Marinas catalin.marinas@arm.com Cc: Christian Borntraeger borntraeger@linux.ibm.com Cc: Christophe Leroy christophe.leroy@csgroup.eu Cc: Heiko Carstens hca@linux.ibm.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Michael Ellerman mpe@ellerman.id.au Cc: Michal Hocko mhocko@suse.com Cc: "Naveen N. Rao" naveen.n.rao@linux.ibm.com Cc: Nicholas Piggin npiggin@gmail.com Cc: Peter Zijlstra (Intel) peterz@infradead.org Cc: Sven Schnelle svens@linux.ibm.com Cc: Vasily Gorbik gor@linux.ibm.com Cc: Will Deacon will@kernel.org Cc: Yin Fengwei fengwei.yin@intel.com Signed-off-by: Andrew Morton akpm@linux-foundation.org (cherry picked from commit d7f861b9c43aadbe384ab1382d2e76750bedc91e) Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com --- arch/s390/include/asm/tlb.h | 17 +++++++++++ include/asm-generic/tlb.h | 8 +++++ include/linux/mm_types.h | 20 ++++++++++++ mm/mmu_gather.c | 61 +++++++++++++++++++++++++++++++------ mm/swap.c | 12 ++++++-- mm/swap_state.c | 15 +++++++-- 6 files changed, 119 insertions(+), 14 deletions(-)
diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h index 1eb1df478e0c..b76c8f028bad 100644 --- a/arch/s390/include/asm/tlb.h +++ b/arch/s390/include/asm/tlb.h @@ -26,6 +26,8 @@ void __tlb_remove_table(void *_table); static inline void tlb_flush(struct mmu_gather *tlb); static inline bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, bool delay_rmap, int page_size); +static inline bool __tlb_remove_folio_pages(struct mmu_gather *tlb, + struct page *page, unsigned int nr_pages, bool delay_rmap);
#define tlb_flush tlb_flush #define pte_free_tlb pte_free_tlb @@ -52,6 +54,21 @@ static inline bool __tlb_remove_page_size(struct mmu_gather *tlb, return false; }
+static inline bool __tlb_remove_folio_pages(struct mmu_gather *tlb, + struct page *page, unsigned int nr_pages, bool delay_rmap) +{ + struct encoded_page *encoded_pages[] = { + encode_page(page, ENCODED_PAGE_BIT_NR_PAGES_NEXT), + encode_nr_pages(nr_pages), + }; + + VM_WARN_ON_ONCE(delay_rmap); + VM_WARN_ON_ONCE(page_folio(page) != page_folio(page + nr_pages - 1)); + + free_pages_and_swap_cache(encoded_pages, ARRAY_SIZE(encoded_pages)); + return false; +} + static inline void tlb_flush(struct mmu_gather *tlb) { __tlb_flush_mm_lazy(tlb->mm); diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h index 50ddc0ed7ff0..22384baee10e 100644 --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -70,6 +70,7 @@ * * - tlb_remove_page() / __tlb_remove_page() * - tlb_remove_page_size() / __tlb_remove_page_size() + * - __tlb_remove_folio_pages() * * __tlb_remove_page_size() is the basic primitive that queues a page for * freeing. __tlb_remove_page() assumes PAGE_SIZE. Both will return a @@ -79,6 +80,11 @@ * tlb_remove_page() and tlb_remove_page_size() imply the call to * tlb_flush_mmu() when required and has no return value. * + * __tlb_remove_folio_pages() is similar to __tlb_remove_page(), however, + * instead of removing a single page, remove the given number of consecutive + * pages that are all part of the same (large) folio: just like calling + * __tlb_remove_page() on each page individually. + * * - tlb_change_page_size() * * call before __tlb_remove_page*() to set the current page-size; implies a @@ -263,6 +269,8 @@ struct mmu_gather_batch {
extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, bool delay_rmap, int page_size); +bool __tlb_remove_folio_pages(struct mmu_gather *tlb, struct page *page, + unsigned int nr_pages, bool delay_rmap);
#ifdef CONFIG_SMP /* diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 1aee23c28330..aa17e8c500ce 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -240,6 +240,15 @@ struct encoded_page; /* Perform rmap removal after we have flushed the TLB. */ #define ENCODED_PAGE_BIT_DELAY_RMAP 1ul
+/* + * The next item in an encoded_page array is the "nr_pages" argument, specifying + * the number of consecutive pages starting from this page, that all belong to + * the same folio. For example, "nr_pages" corresponds to the number of folio + * references that must be dropped. If this bit is not set, "nr_pages" is + * implicitly 1. + */ +#define ENCODED_PAGE_BIT_NR_PAGES_NEXT 2ul + static __always_inline struct encoded_page *encode_page(struct page *page, unsigned long flags) { BUILD_BUG_ON(flags > ENCODED_PAGE_BITS); @@ -256,6 +265,17 @@ static inline struct page *encoded_page_ptr(struct encoded_page *page) return (struct page *)(~ENCODED_PAGE_BITS & (unsigned long)page); }
+static __always_inline struct encoded_page *encode_nr_pages(unsigned long nr) +{ + VM_WARN_ON_ONCE((nr << 2) >> 2 != nr); + return (struct encoded_page *)(nr << 2); +} + +static __always_inline unsigned long encoded_nr_pages(struct encoded_page *page) +{ + return ((unsigned long)page) >> 2; +} + /* * A swap entry has to fit into a "unsigned long", as the entry is hidden * in the "index" field of the swapper address space. diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c index 6540c99c6758..d175c0f1e2c8 100644 --- a/mm/mmu_gather.c +++ b/mm/mmu_gather.c @@ -50,12 +50,21 @@ static bool tlb_next_batch(struct mmu_gather *tlb) #ifdef CONFIG_SMP static void tlb_flush_rmap_batch(struct mmu_gather_batch *batch, struct vm_area_struct *vma) { + struct encoded_page **pages = batch->encoded_pages; + for (int i = 0; i < batch->nr; i++) { - struct encoded_page *enc = batch->encoded_pages[i]; + struct encoded_page *enc = pages[i];
if (encoded_page_flags(enc) & ENCODED_PAGE_BIT_DELAY_RMAP) { struct page *page = encoded_page_ptr(enc); - folio_remove_rmap_pte(page_folio(page), page, vma); + unsigned int nr_pages = 1; + + if (unlikely(encoded_page_flags(enc) & + ENCODED_PAGE_BIT_NR_PAGES_NEXT)) + nr_pages = encoded_nr_pages(pages[++i]); + + folio_remove_rmap_ptes(page_folio(page), page, nr_pages, + vma); } } } @@ -89,18 +98,26 @@ static void tlb_batch_pages_flush(struct mmu_gather *tlb) for (batch = &tlb->local; batch && batch->nr; batch = batch->next) { struct encoded_page **pages = batch->encoded_pages;
- do { + while (batch->nr) { /* * limit free batch count when PAGE_SIZE > 4K */ unsigned int nr = min(512U, batch->nr);
+ /* + * Make sure we cover page + nr_pages, and don't leave + * nr_pages behind when capping the number of entries. + */ + if (unlikely(encoded_page_flags(pages[nr - 1]) & + ENCODED_PAGE_BIT_NR_PAGES_NEXT)) + nr++; + free_pages_and_swap_cache(pages, nr); pages += nr; batch->nr -= nr;
cond_resched(); - } while (batch->nr); + } } tlb->active = &tlb->local; } @@ -116,8 +133,9 @@ static void tlb_batch_list_free(struct mmu_gather *tlb) tlb->local.next = NULL; }
-bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, - bool delay_rmap, int page_size) +static bool __tlb_remove_folio_pages_size(struct mmu_gather *tlb, + struct page *page, unsigned int nr_pages, bool delay_rmap, + int page_size) { int flags = delay_rmap ? ENCODED_PAGE_BIT_DELAY_RMAP : 0; struct mmu_gather_batch *batch; @@ -126,6 +144,8 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
#ifdef CONFIG_MMU_GATHER_PAGE_SIZE VM_WARN_ON(tlb->page_size != page_size); + VM_WARN_ON_ONCE(nr_pages != 1 && page_size != PAGE_SIZE); + VM_WARN_ON_ONCE(page_folio(page) != page_folio(page + nr_pages - 1)); #endif
batch = tlb->active; @@ -133,17 +153,40 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, * Add the page and check if we are full. If so * force a flush. */ - batch->encoded_pages[batch->nr++] = encode_page(page, flags); - if (batch->nr == batch->max) { + if (likely(nr_pages == 1)) { + batch->encoded_pages[batch->nr++] = encode_page(page, flags); + } else { + flags |= ENCODED_PAGE_BIT_NR_PAGES_NEXT; + batch->encoded_pages[batch->nr++] = encode_page(page, flags); + batch->encoded_pages[batch->nr++] = encode_nr_pages(nr_pages); + } + /* + * Make sure that we can always add another "page" + "nr_pages", + * requiring two entries instead of only a single one. + */ + if (batch->nr >= batch->max - 1) { if (!tlb_next_batch(tlb)) return true; batch = tlb->active; } - VM_BUG_ON_PAGE(batch->nr > batch->max, page); + VM_BUG_ON_PAGE(batch->nr > batch->max - 1, page);
return false; }
+bool __tlb_remove_folio_pages(struct mmu_gather *tlb, struct page *page, + unsigned int nr_pages, bool delay_rmap) +{ + return __tlb_remove_folio_pages_size(tlb, page, nr_pages, delay_rmap, + PAGE_SIZE); +} + +bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, + bool delay_rmap, int page_size) +{ + return __tlb_remove_folio_pages_size(tlb, page, 1, delay_rmap, page_size); +} + #endif /* MMU_GATHER_NO_GATHER */
#ifdef CONFIG_MMU_GATHER_TABLE_FREE diff --git a/mm/swap.c b/mm/swap.c index cd8f0150ba3a..e5380d732c0d 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -967,11 +967,17 @@ void release_pages(release_pages_arg arg, int nr) unsigned int lock_batch;
for (i = 0; i < nr; i++) { + unsigned int nr_refs = 1; struct folio *folio;
/* Turn any of the argument types into a folio */ folio = page_folio(encoded_page_ptr(encoded[i]));
+ /* Is our next entry actually "nr_pages" -> "nr_refs" ? */ + if (unlikely(encoded_page_flags(encoded[i]) & + ENCODED_PAGE_BIT_NR_PAGES_NEXT)) + nr_refs = encoded_nr_pages(encoded[++i]); + /* * Make sure the IRQ-safe lock-holding time does not get * excessive with a continuous string of pages from the @@ -990,14 +996,14 @@ void release_pages(release_pages_arg arg, int nr) unlock_page_lruvec_irqrestore(lruvec, flags); lruvec = NULL; } - if (put_devmap_managed_page(&folio->page)) + if (put_devmap_managed_page_refs(&folio->page, nr_refs)) continue; - if (folio_put_testzero(folio)) + if (folio_ref_sub_and_test(folio, nr_refs)) free_zone_device_page(&folio->page); continue; }
- if (!folio_put_testzero(folio)) + if (!folio_ref_sub_and_test(folio, nr_refs)) continue;
if (folio_test_large(folio)) { diff --git a/mm/swap_state.c b/mm/swap_state.c index ddb3a65e5c6e..d0636532d1ab 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -311,8 +311,19 @@ void free_page_and_swap_cache(struct page *page) void free_pages_and_swap_cache(struct encoded_page **pages, int nr) { lru_add_drain(); - for (int i = 0; i < nr; i++) - free_swap_cache(encoded_page_ptr(pages[i])); + for (int i = 0; i < nr; i++) { + struct page *page = encoded_page_ptr(pages[i]); + + /* + * Skip over the "nr_pages" entry. It's sufficient to call + * free_swap_cache() only once per folio. + */ + if (unlikely(encoded_page_flags(pages[i]) & + ENCODED_PAGE_BIT_NR_PAGES_NEXT)) + i++; + + free_swap_cache(page); + } release_pages(pages, nr); }