The patch titled powerpc: lockless get_user_pages has been removed from the -mm tree. Its filename was powerpc-lockless-get_user_pages.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: powerpc: lockless get_user_pages From: Nick Piggin <npiggin@xxxxxxx> Implement lockless get_user_pages_fast for powerpc. Page table existence is guaranteed with RCU, and speculative page references are used to take a reference to the pages without having a prior existence guarantee on them. Signed-off-by: Nick Piggin <npiggin@xxxxxxx> Signed-off-by: Dave Kleikamp <shaggy@xxxxxxxxxxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Hugh Dickins <hugh@xxxxxxxxxxx> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/powerpc/Kconfig | 3 arch/powerpc/mm/Makefile | 2 arch/powerpc/mm/gup.c | 258 ++++++++++++++++++++++++++ include/asm-powerpc/pgtable-ppc64.h | 2 include/linux/pagemap.h | 23 ++ 5 files changed, 287 insertions(+), 1 deletion(-) diff -puN arch/powerpc/Kconfig~powerpc-lockless-get_user_pages arch/powerpc/Kconfig --- a/arch/powerpc/Kconfig~powerpc-lockless-get_user_pages +++ a/arch/powerpc/Kconfig @@ -42,6 +42,9 @@ config GENERIC_HARDIRQS bool default y +config HAVE_GET_USER_PAGES_FAST + def_bool PPC64 + config HAVE_SETUP_PER_CPU_AREA def_bool PPC64 diff -puN arch/powerpc/mm/Makefile~powerpc-lockless-get_user_pages arch/powerpc/mm/Makefile --- a/arch/powerpc/mm/Makefile~powerpc-lockless-get_user_pages +++ a/arch/powerpc/mm/Makefile @@ -6,7 +6,7 @@ ifeq ($(CONFIG_PPC64),y) EXTRA_CFLAGS += -mno-minimal-toc endif -obj-y := fault.o mem.o \ +obj-y := fault.o mem.o gup.o \ init_$(CONFIG_WORD_SIZE).o \ pgtable_$(CONFIG_WORD_SIZE).o \ mmu_context_$(CONFIG_WORD_SIZE).o diff -puN /dev/null arch/powerpc/mm/gup.c --- /dev/null +++ a/arch/powerpc/mm/gup.c @@ -0,0 +1,258 @@ +/* + * Lockless get_user_pages_fast for powerpc + * + * Copyright (C) 2008 Nick Piggin + * Copyright (C) 2008 Novell Inc. + */ +#include <linux/sched.h> +#include <linux/mm.h> +#include <linux/hugetlb.h> +#include <linux/vmstat.h> +#include <linux/pagemap.h> +#include <linux/rwsem.h> +#include <asm/pgtable.h> + +/* + * The performance critical leaf functions are made noinline otherwise gcc + * inlines everything into a single function which results in too much + * register pressure. + */ +static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, + unsigned long end, int write, struct page **pages, int *nr) +{ + unsigned long mask, result; + pte_t *ptep; + + result = _PAGE_PRESENT|_PAGE_USER; + if (write) + result |= _PAGE_RW; + mask = result | _PAGE_SPECIAL; + + ptep = pte_offset_kernel(&pmd, addr); + do { + pte_t pte = *ptep; + struct page *page; + + if ((pte_val(pte) & mask) != result) + return 0; + VM_BUG_ON(!pfn_valid(pte_pfn(pte))); + page = pte_page(pte); + if (!page_cache_get_speculative(page)) + return 0; + if (unlikely(pte != *ptep)) { + put_page(page); + return 0; + } + pages[*nr] = page; + (*nr)++; + + } while (ptep++, addr += PAGE_SIZE, addr != end); + + return 1; +} + +static noinline int gup_huge_pte(pte_t *ptep, struct hstate *hstate, + unsigned long *addr, unsigned long end, + int write, struct page **pages, int *nr) +{ + unsigned long mask; + unsigned long pte_end; + struct page *head, *page; + pte_t pte; + int refs; + + pte_end = (*addr + huge_page_size(hstate)) & huge_page_mask(hstate); + if (pte_end < end) + end = pte_end; + + pte = *ptep; + mask = _PAGE_PRESENT|_PAGE_USER; + if (write) + mask |= _PAGE_RW; + if ((pte_val(pte) & mask) != mask) + return 0; + /* hugepages are never "special" */ + VM_BUG_ON(!pfn_valid(pte_pfn(pte))); + + refs = 0; + head = pte_page(pte); + page = head + ((*addr & ~huge_page_mask(hstate)) >> PAGE_SHIFT); + do { + VM_BUG_ON(compound_head(page) != head); + pages[*nr] = page; + (*nr)++; + page++; + refs++; + } while (*addr += PAGE_SIZE, *addr != end); + + if (!page_cache_add_speculative(head, refs)) { + *nr -= refs; + return 0; + } + if (unlikely(pte != *ptep)) { + /* Could be optimized better */ + while (*nr) { + put_page(page); + (*nr)--; + } + } + + return 1; +} + +static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, + int write, struct page **pages, int *nr) +{ + unsigned long next; + pmd_t *pmdp; + + pmdp = pmd_offset(&pud, addr); + do { + pmd_t pmd = *pmdp; + + next = pmd_addr_end(addr, end); + if (pmd_none(pmd)) + return 0; + if (!gup_pte_range(pmd, addr, next, write, pages, nr)) + return 0; + } while (pmdp++, addr = next, addr != end); + + return 1; +} + +static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, + int write, struct page **pages, int *nr) +{ + unsigned long next; + pud_t *pudp; + + pudp = pud_offset(&pgd, addr); + do { + pud_t pud = *pudp; + + next = pud_addr_end(addr, end); + if (pud_none(pud)) + return 0; + if (!gup_pmd_range(pud, addr, next, write, pages, nr)) + return 0; + } while (pudp++, addr = next, addr != end); + + return 1; +} + +int get_user_pages_fast(unsigned long start, int nr_pages, int write, + struct page **pages) +{ + struct mm_struct *mm = current->mm; + unsigned long end = start + (nr_pages << PAGE_SHIFT); + unsigned long addr = start; + unsigned long next; + pgd_t *pgdp; + int nr = 0; + unsigned int shift; + + + if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, + start, nr_pages*PAGE_SIZE))) + goto slow_irqon; + + /* Cross a slice boundary? */ + if (addr < SLICE_LOW_TOP) { + if (end > SLICE_LOW_TOP) + goto slow_irqon; + + if (unlikely(GET_LOW_SLICE_INDEX(addr) != + GET_LOW_SLICE_INDEX(end - 1))) + goto slow_irqon; + } else { + if (unlikely(GET_HIGH_SLICE_INDEX(addr) != + GET_HIGH_SLICE_INDEX(end - 1))) + goto slow_irqon; + } + + /* + * XXX: batch / limit 'nr', to avoid large irq off latency + * needs some instrumenting to determine the common sizes used by + * important workloads (eg. DB2), and whether limiting the batch size + * will decrease performance. + * + * It seems like we're in the clear for the moment. Direct-IO is + * the main guy that batches up lots of get_user_pages, and even + * they are limited to 64-at-a-time which is not so many. + */ + /* + * This doesn't prevent pagetable teardown, but does prevent + * the pagetables from being freed on powerpc. + * + * So long as we atomically load page table pointers versus teardown, + * we can follow the address down to the the page and take a ref on it. + */ + local_irq_disable(); + + shift = mmu_psize_defs[get_slice_psize(mm, addr)].shift; + + if (shift > PAGE_SHIFT) { + pte_t *ptep; + unsigned long a = addr; + unsigned long sz = ((1UL) << shift); + struct hstate *hstate = size_to_hstate(sz); + + BUG_ON(!hstate); + /* + * XXX: could be optimized to avoid hstate + * lookup entirely (just use shift) + */ + + ptep = huge_pte_offset(mm, a); + do { + VM_BUG_ON(shift != mmu_psize_defs[get_slice_psize(mm, a)].shift); + if (!gup_huge_pte(ptep, hstate, &a, end, write, pages, + &nr)) + goto slow; + ptep++; + } while (a != end); + } else { + pgdp = pgd_offset(mm, addr); + do { + pgd_t pgd = *pgdp; + + VM_BUG_ON(shift != mmu_psize_defs[get_slice_psize(mm, addr)].shift); + + next = pgd_addr_end(addr, end); + if (pgd_none(pgd)) + goto slow; + if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) + goto slow; + } while (pgdp++, addr = next, addr != end); + } + local_irq_enable(); + + VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); + return nr; + + { + int ret; + +slow: + local_irq_enable(); +slow_irqon: + /* Try to get the remaining pages with get_user_pages */ + start += nr << PAGE_SHIFT; + pages += nr; + + down_read(&mm->mmap_sem); + ret = get_user_pages(current, mm, start, + (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); + up_read(&mm->mmap_sem); + + /* Have to be a bit careful with return values */ + if (nr > 0) { + if (ret < 0) + ret = nr; + else + ret += nr; + } + + return ret; + } +} diff -puN include/asm-powerpc/pgtable-ppc64.h~powerpc-lockless-get_user_pages include/asm-powerpc/pgtable-ppc64.h --- a/include/asm-powerpc/pgtable-ppc64.h~powerpc-lockless-get_user_pages +++ a/include/asm-powerpc/pgtable-ppc64.h @@ -461,6 +461,8 @@ void pgtable_cache_init(void); return pt; } +pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long address); + #endif /* __ASSEMBLY__ */ #endif /* _ASM_POWERPC_PGTABLE_PPC64_H_ */ diff -puN include/linux/pagemap.h~powerpc-lockless-get_user_pages include/linux/pagemap.h --- a/include/linux/pagemap.h~powerpc-lockless-get_user_pages +++ a/include/linux/pagemap.h @@ -143,6 +143,29 @@ static inline int page_cache_get_specula return 1; } +/* + * Same as above, but add instead of inc (could just be merged) + */ +static inline int page_cache_add_speculative(struct page *page, int count) +{ + VM_BUG_ON(in_interrupt()); + +#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU) +# ifdef CONFIG_PREEMPT + VM_BUG_ON(!in_atomic()); +# endif + VM_BUG_ON(page_count(page) == 0); + atomic_add(count, &page->_count); + +#else + if (unlikely(!atomic_add_unless(&page->_count, count, 0))) + return 0; +#endif + VM_BUG_ON(PageCompound(page) && page != compound_head(page)); + + return 1; +} + static inline int page_freeze_refs(struct page *page, int count) { return likely(atomic_cmpxchg(&page->_count, count, 0) == count); _ Patches currently in -mm which might be from npiggin@xxxxxxx are origin.patch linux-next.patch vmscan-move-isolate_lru_page-to-vmscanc.patch mlock-mlocked-pages-are-unevictable.patch mmap-handle-mlocked-pages-during-map-remap-unmap.patch vmstat-mlocked-pages-statistics.patch reiser4.patch likeliness-accounting-change-and-cleanup.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html