操作系统第十次实验
张焓
1.实验名称：
虚拟内存管理算法
2.实验目的：
1.分析算法设计原理； 2.写出算法伪代码；
3.从算法的执行效率等方面分析算法的性能。
3.实验方法
通过阅读linux内核代码中管理虚拟内存的代码段学习虚拟内存管理算法的原理。
4.实验步骤
(1)mm_struct结构体，定义了每个进程的虚拟存储用户区，首地址在任务结构体中，定义在/include/linux/schedul.h中
structmm_struct { */
spinlock_t page_table_lock;
/* Protects page tables and some counters */
unsignedlong task_size; pgd_t * pgd; atomic_t mm_users; atomic_t mm_count;
/* How many users with user space? */
/* How many references to \/* PTE page table pages */ /* PMD page table pages */ /* number of VMAs */
/* size of task vm space */
/* highest vma end address */
unsignedlong highest_vm_end; structvm_area_struct *mmap; structrb_root mm_rb;
u32 vmacache_seqnum; /* per-thread vmacache */ unsignedlong (*get_unmapped_area) (struct file *filp,
unsignedlong addr, unsignedlong len, unsignedlong pgoff, unsignedlong flags);
/* base of mmap area */
/* list of VMAs */
#ifdef CONFIG_MMU
#endif
unsignedlong mmap_base;
unsignedlong mmap_legacy_base; /* base of mmap area in bottom-up allocations
count as 1) */
atomic_long_t nr_ptes; atomic_long_t nr_pmds; int map_count;
#if CONFIG_PGTABLE_LEVELS > 2 #endif
structrw_semaphore mmap_sem; structlist_head mmlist;
/* List of maybe swapped mm's. These are globally
strung
* together off init_mm.mmlist, and are protected * by mmlist_lock */
unsignedlong hiwater_rss; /* High-watermark of RSS usage */ unsignedlong hiwater_vm; /* High-water virtual memory usage */ unsignedlong total_vm; unsignedlong locked_vm; unsignedlong pinned_vm; unsignedlong data_vm; unsignedlong exec_vm; unsignedlong stack_vm; unsignedlong def_flags;
unsignedlong start_code, end_code, start_data, end_data; unsignedlong start_brk, brk, start_stack;
unsignedlong arg_start, arg_end, env_start, env_end;
unsignedlong saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */ /*
* Special counters, in some configurations protected by the * page_table_lock, in other configurations by being atomic. */
structmm_rss_stat rss_stat; structlinux_binfmt *binfmt; cpumask_var_t cpu_vm_mask_var;
/* Architecture-specific MM context */ mm_context_t context;
unsignedlong flags; /* Must use atomic bitops to access the bits */ structcore_state *core_state; /* coredumping support */ spinlock_t
ioctx_lock;
/* Total pages mapped */
/* Pages that have PG_mlocked set */ /* Refcount permanently increased */ /* VM_WRITE & ~VM_SHARED & ~VM_STACK */ /* VM_EXEC & ~VM_WRITE & ~VM_STACK */ /* VM_STACK */
#ifdef CONFIG_AIO
struct kioctx_table __rcu *ioctx_table;
#endif
#ifdef CONFIG_MEMCG
/* store ref to file /proc/
struct mmu_notifier_mm *mmu_notifier_mm; /*
* \ * user/owner of this mm. All of the following must be true in * order for it to be changed: *
* current == mm->owner * current->mm != mm * new_owner->mm == mm
* new_owner->alloc_lock is held */
struct task_struct __rcu *owner;
#endif
#ifdef CONFIG_MMU_NOTIFIER #endif
#ifdefined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
pgtable_t pmd_huge_pte; /* protected by page_table_lock */ #endif
#ifdef CONFIG_CPUMASK_OFFSTACK
struct cpumask cpumask_allocation; #endif
#ifdef CONFIG_NUMA_BALANCING
/* numa_scan_seq prevents two threads setting pte_numa */ int numa_scan_seq;
/* Restart point for scanning and setting pte_numa */ unsignedlong numa_scan_offset; /*
* numa_next_scan is the next time that the PTEs will be marked * pte_numa. NUMA hinting faults will gather statistics and migrate * pages to new nodes if necessary. */
unsignedlong numa_next_scan;
#endif
#ifdefined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION)
/*
* An operation with batched TLB flushing is going on. Anything that * can move process memory needs to flush the TLB when moving a
* PROT_NONE or PROT_NUMA mapped page. */
bool tlb_flush_pending;
structuprobes_state uprobes_state; /* address of the bounds directory */ void __user *bd_addr;
#endif
#ifdef CONFIG_X86_INTEL_MPX
#endif
#ifdef CONFIG_HUGETLB_PAGE
atomic_long_t hugetlb_usage; #endif
#ifdef CONFIG_MMU };
struct work_struct async_put_work; #endif
(2)进程虚存区域，一个虚存区域是许村空间中一个连续区域，每个虚拟区域用一个vm_area_struct结构体描述，定义在/include/linux/mm_type.h中；
structvm_area_struct {
structmm_struct *vm_mm; pgprot_t vm_page_prot; unsignedlong vm_flags;
/* The address space we belong to. */ /* Access permissions of this VMA. */ /* Flags, see mm.h. */
/* Second cache line starts here. */ /*
* Largest free memory gap in bytes to the left of this VMA. * Either between this VMA and vma->vm_prev, or between one of the * VMAs below us in the VMA rbtree and its ->vm_prev. This helps * get_unmapped_area find a free area of the right size. */
unsignedlong rb_subtree_gap; structrb_node vm_rb;
/* linked list of VM areas per task, sorted by address */ structvm_area_struct *vm_next, *vm_prev; unsignedlong vm_start; unsignedlong vm_end;
/* Our start address within vm_mm. */ /* The first byte after our end address
/* The first cache line has the info for VMA tree walking. */
within vm_mm. */
#ifndef CONFIG_MMU
structvm_region *vm_region;
/* NOMMU mapping region */
#endif
#ifdef CONFIG_NUMA };
struct mempolicy *vm_policy; /* NUMA policy for the VMA */ structvm_userfaultfd_ctx vm_userfaultfd_ctx; #endif
/* Information about our backing store: */ unsignedlong vm_pgoff;
structfile * vm_file; void * vm_private_data;
/* Offset (within vm_file) in PAGE_SIZE /* File we map to (can be NULL). */
/* was vm_pte (shared mem) */
units */
/* Function pointers to deal with this struct. */ conststructvm_operations_struct *vm_ops; /*
* A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma * list, after a COW of one of the file pages. A MAP_SHARED vma * can only be in the i_mmap tree. An anonymous MAP_PRIVATE, stack * or brk vma (with NULL file) can only be in an anon_vma list. */
structlist_head anon_vma_chain; /* Serialized by mmap_sem &
* page_table_lock */
structanon_vma *anon_vma; /* Serialized by page_table_lock */ /*
* For areas with an address space and backing store, * linkage into the address_space->i_mmap interval tree. */ struct {
structrb_node rb;
unsignedlong rb_subtree_last;
} shared;
(3)linux使用do_mmap()函数完成可执行映像向虚存区域的映射，建立有关的虚存区域，定义在/mm/mmap.c中；
unsignedlong do_mmap(structfile *file, unsignedlongaddr,
unsignedlonglen, unsignedlongprot, unsignedlongflags, vm_flags_t vm_flags, unsignedlongpgoff, unsignedlong *populate)
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