diff options
Diffstat (limited to 'include/asm-generic/tlb.h')
| -rw-r--r-- | include/asm-generic/tlb.h | 156 |
1 files changed, 86 insertions, 70 deletions
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h index e43f9766259f..e58fa777fa09 100644 --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -5,6 +5,8 @@ * Copyright 2001 Red Hat, Inc. * Based on code from mm/memory.c Copyright Linus Torvalds and others. * + * Copyright 2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> + * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version @@ -17,97 +19,111 @@ #include <asm/pgalloc.h> #include <asm/tlbflush.h> +#ifdef CONFIG_HAVE_RCU_TABLE_FREE /* - * For UP we don't need to worry about TLB flush - * and page free order so much.. + * Semi RCU freeing of the page directories. + * + * This is needed by some architectures to implement software pagetable walkers. + * + * gup_fast() and other software pagetable walkers do a lockless page-table + * walk and therefore needs some synchronization with the freeing of the page + * directories. The chosen means to accomplish that is by disabling IRQs over + * the walk. + * + * Architectures that use IPIs to flush TLBs will then automagically DTRT, + * since we unlink the page, flush TLBs, free the page. Since the disabling of + * IRQs delays the completion of the TLB flush we can never observe an already + * freed page. + * + * Architectures that do not have this (PPC) need to delay the freeing by some + * other means, this is that means. + * + * What we do is batch the freed directory pages (tables) and RCU free them. + * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling + * holds off grace periods. + * + * However, in order to batch these pages we need to allocate storage, this + * allocation is deep inside the MM code and can thus easily fail on memory + * pressure. To guarantee progress we fall back to single table freeing, see + * the implementation of tlb_remove_table_one(). + * */ -#ifdef CONFIG_SMP - #ifdef ARCH_FREE_PTR_NR - #define FREE_PTR_NR ARCH_FREE_PTR_NR - #else - #define FREE_PTE_NR 506 - #endif - #define tlb_fast_mode(tlb) ((tlb)->nr == ~0U) -#else - #define FREE_PTE_NR 1 - #define tlb_fast_mode(tlb) 1 +struct mmu_table_batch { + struct rcu_head rcu; + unsigned int nr; + void *tables[0]; +}; + +#define MAX_TABLE_BATCH \ + ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *)) + +extern void tlb_table_flush(struct mmu_gather *tlb); +extern void tlb_remove_table(struct mmu_gather *tlb, void *table); + #endif -/* struct mmu_gather is an opaque type used by the mm code for passing around - * any data needed by arch specific code for tlb_remove_page. +/* + * If we can't allocate a page to make a big batch of page pointers + * to work on, then just handle a few from the on-stack structure. */ -struct mmu_gather { - struct mm_struct *mm; - unsigned int nr; /* set to ~0U means fast mode */ - unsigned int need_flush;/* Really unmapped some ptes? */ - unsigned int fullmm; /* non-zero means full mm flush */ - struct page * pages[FREE_PTE_NR]; +#define MMU_GATHER_BUNDLE 8 + +struct mmu_gather_batch { + struct mmu_gather_batch *next; + unsigned int nr; + unsigned int max; + struct page *pages[0]; }; -/* Users of the generic TLB shootdown code must declare this storage space. */ -DECLARE_PER_CPU(struct mmu_gather, mmu_gathers); +#define MAX_GATHER_BATCH \ + ((PAGE_SIZE - sizeof(struct mmu_gather_batch)) / sizeof(void *)) -/* tlb_gather_mmu - * Return a pointer to an initialized struct mmu_gather. +/* struct mmu_gather is an opaque type used by the mm code for passing around + * any data needed by arch specific code for tlb_remove_page. */ -static inline struct mmu_gather * -tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush) -{ - struct mmu_gather *tlb = &get_cpu_var(mmu_gathers); - - tlb->mm = mm; +struct mmu_gather { + struct mm_struct *mm; +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + struct mmu_table_batch *batch; +#endif + unsigned int need_flush : 1, /* Did free PTEs */ + fast_mode : 1; /* No batching */ - /* Use fast mode if only one CPU is online */ - tlb->nr = num_online_cpus() > 1 ? 0U : ~0U; + unsigned int fullmm; - tlb->fullmm = full_mm_flush; + struct mmu_gather_batch *active; + struct mmu_gather_batch local; + struct page *__pages[MMU_GATHER_BUNDLE]; +}; - return tlb; -} +#define HAVE_GENERIC_MMU_GATHER -static inline void -tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end) +static inline int tlb_fast_mode(struct mmu_gather *tlb) { - if (!tlb->need_flush) - return; - tlb->need_flush = 0; - tlb_flush(tlb); - if (!tlb_fast_mode(tlb)) { - free_pages_and_swap_cache(tlb->pages, tlb->nr); - tlb->nr = 0; - } +#ifdef CONFIG_SMP + return tlb->fast_mode; +#else + /* + * For UP we don't need to worry about TLB flush + * and page free order so much.. + */ + return 1; +#endif } -/* tlb_finish_mmu - * Called at the end of the shootdown operation to free up any resources - * that were required. - */ -static inline void -tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end) -{ - tlb_flush_mmu(tlb, start, end); - - /* keep the page table cache within bounds */ - check_pgt_cache(); - - put_cpu_var(mmu_gathers); -} +void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm); +void tlb_flush_mmu(struct mmu_gather *tlb); +void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end); +int __tlb_remove_page(struct mmu_gather *tlb, struct page *page); /* tlb_remove_page - * Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while - * handling the additional races in SMP caused by other CPUs caching valid - * mappings in their TLBs. + * Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when + * required. */ static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page) { - tlb->need_flush = 1; - if (tlb_fast_mode(tlb)) { - free_page_and_swap_cache(page); - return; - } - tlb->pages[tlb->nr++] = page; - if (tlb->nr >= FREE_PTE_NR) - tlb_flush_mmu(tlb, 0, 0); + if (!__tlb_remove_page(tlb, page)) + tlb_flush_mmu(tlb); } /** |