| 日期 | 內核版本 | 架構 | 作者 | GitHub | CSDN |
|---|---|---|---|---|---|
| 2017-07-04 | Linux-4.12 | X86 | lwhuq | LinuxMemoryStudy | Linux內存管理 |
在NUMA多CPU架構下，每個CPU後面都有掛載本地內存，CPU之前通過總線連接。每個CPU在訪問當地內存的速度都會比訪問遠程內存速度快。Linux系統下把每個CPU的本地內存資源用一個結點node表示。
1 pg_data_t結構
pg_data_t的定義在include/linux/mmzone.h#L601
typedef struct pglist_data {
//一個結構數組，包含了結點中各內存域的數據結構zone
struct zone node_zones[MAX_NR_ZONES];
//指定了備用結點機器內存域的列表，以便在當前結點沒有可用空間時，在備用結點分配內存
struct zonelist node_zonelists[MAX_ZONELISTS];
//內存域的個數
int nr_zones;
#ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */
//指向結點的第一個頁框的頁結構，該頁結構位於全局mem_map中某個位置
struct page *node_mem_map;
#ifdef CONFIG_PAGE_EXTENSION
struct page_ext *node_page_ext;
#endif
#endif
#ifndef CONFIG_NO_BOOTMEM
//啓動內存分配器
struct bootmem_data *bdata;
#endif
#ifdef CONFIG_MEMORY_HOTPLUG
/*
* Must be held any time you expect node_start_pfn, node_present_pages
* or node_spanned_pages stay constant. Holding this will also
* guarantee that any pfn_valid() stays that way.
*
* pgdat_resize_lock() and pgdat_resize_unlock() are provided to
* manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
*
* Nests above zone->lock and zone->span_seqlock
*/
spinlock_t node_size_lock;
#endif
//結點起始頁框
unsigned long node_start_pfn;
//結點總頁框數（不包含洞）
unsigned long node_present_pages; /* total number of physical pages */
//結點總頁框數（包含洞）
unsigned long node_spanned_pages; /* total size of physical page
range, including holes */
//結點id
int node_id;
//交換守護進程的等待列表
wait_queue_head_t kswapd_wait;
//本結點交換守護進程
wait_queue_head_t pfmemalloc_wait;
struct task_struct *kswapd; /* Protected by
mem_hotplug_begin/end() */
int kswapd_order;
enum zone_type kswapd_classzone_idx;
int kswapd_failures; /* Number of 'reclaimed == 0' runs */
#ifdef CONFIG_COMPACTION
int kcompactd_max_order;
enum zone_type kcompactd_classzone_idx;
wait_queue_head_t kcompactd_wait;
struct task_struct *kcompactd;
#endif
#ifdef CONFIG_NUMA_BALANCING
/* Lock serializing the migrate rate limiting window */
spinlock_t numabalancing_migrate_lock;
/* Rate limiting time interval */
unsigned long numabalancing_migrate_next_window;
/* Number of pages migrated during the rate limiting time interval */
unsigned long numabalancing_migrate_nr_pages;
#endif
/*
* This is a per-node reserve of pages that are not available
* to userspace allocations.
*/
unsigned long totalreserve_pages;
#ifdef CONFIG_NUMA
/*
* zone reclaim becomes active if more unmapped pages exist.
*/
unsigned long min_unmapped_pages;
unsigned long min_slab_pages;
#endif /* CONFIG_NUMA */
/* Write-intensive fields used by page reclaim */
ZONE_PADDING(_pad1_)
spinlock_t lru_lock;
#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
/*
* If memory initialisation on large machines is deferred then this
* is the first PFN that needs to be initialised.
*/
unsigned long first_deferred_pfn;
unsigned long static_init_size;
#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
spinlock_t split_queue_lock;
struct list_head split_queue;
unsigned long split_queue_len;
#endif
/* Fields commonly accessed by the page reclaim scanner */
struct lruvec lruvec;
/*
* The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
* this node's LRU. Maintained by the pageout code.
*/
unsigned int inactive_ratio;
unsigned long flags;
ZONE_PADDING(_pad2_)
/* Per-node vmstats */
struct per_cpu_nodestat __percpu *per_cpu_nodestats;
atomic_long_t vm_stat[NR_VM_NODE_STAT_ITEMS];
} pg_data_t;1.1 結點的內存域
結點管理的內存再細分成內存域。typedef struct pglist_data {
//一個結構數組，包含了結點中各內存域的數據結構zone
struct zone node_zones[MAX_NR_ZONES];
//指定了備用結點機器內存域的列表，以便在當前結點沒有可用空間時，在備用結點分配內存
struct zonelist node_zonelists[MAX_ZONELISTS];
//內存域的個數
int nr_zones;
}- node_zones[MAX_NR_ZONES]管理着本地內存的最多MAX_NR_ZONES個內存域
- node_zonelists[MAX_ZONELISTS]指定了備用結點及內存域的列表。可以想象這些備用結點及內存域都是遠程內存
- nr_zones結點內存域的個數
1.2 結點的內存頁
typedef struct pglist_data {
#ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */
struct page *node_mem_map; //指向結點的第一個頁框的頁結構，該頁結構位於全局mem_map中某個位置
#ifdef CONFIG_PAGE_EXTENSION
struct page_ext *node_page_ext;
#endif
#endif
//結點起始頁框
unsigned long node_start_pfn;
//結點總頁框數（不包含洞）
unsigned long node_present_pages; /* total number of physical pages */
//結點總頁框數（包含洞）
unsigned long node_spanned_pages; /* total size of physical page range, including holes */
} pg_data_t;在每個結點的結構pg_data_t內有一個指向頁結構page的指針node_mem_map。pg_data_t->node_mem_map指向本結點管理的物理內存頁框的第一個頁框。
typedef struct pglist_data {
//指向結點的第一個頁框的頁結構，該頁結構位於全局mem_map中某個位置
struct page *node_mem_map;
} pg_data_t->node_mem_map的初始化在alloc_node_mem_map中完成，定義在mm/page_alloc.c#L6096
static void __ref alloc_node_mem_map(struct pglist_data *pgdat)
{
start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1);
offset = pgdat->node_start_pfn - start;
/* ia64 gets its own node_mem_map, before this, without bootmem */
if (!pgdat->node_mem_map) {
unsigned long size, end;
struct page *map;
/*
* The zone's endpoints aren't required to be MAX_ORDER
* aligned but the node_mem_map endpoints must be in order
* for the buddy allocator to function correctly.
*/
end = pgdat_end_pfn(pgdat);
end = ALIGN(end, MAX_ORDER_NR_PAGES);
size = (end - start) * sizeof(struct page);
map = alloc_remap(pgdat->node_id, size);
if (!map)
map = memblock_virt_alloc_node_nopanic(size,
pgdat->node_id);
pgdat->node_mem_map = map + offset;
}
}1.3 交換守護進程
typedef struct pglist_data {
//交換守護進程的等待列表
wait_queue_head_t kswapd_wait;wait_queue_head_t pfmemalloc_wait;
//本結點交換守護進程
struct task_struct *kswapd; /* Protected by mem_hotplug_begin/end() */
int kswapd_order;
enum zone_type kswapd_classzone_idx;
int kswapd_failures; /* Number of 'reclaimed == 0' runs */
} pg_data_t;2 結點狀態
當系統中有超過一個結點時，內核會維護一個位圖node_states用以提供各個結點的狀態信息，其定義在include/linux/nodemask.h#L381enum node_states {
N_POSSIBLE, /* The node could become online at some point */
N_ONLINE, /* The node is online */
N_NORMAL_MEMORY, /* The node has regular memory */
#ifdef CONFIG_HIGHMEM
N_HIGH_MEMORY, /* The node has regular or high memory */
#else
N_HIGH_MEMORY = N_NORMAL_MEMORY,
#endif
#ifdef CONFIG_MOVABLE_NODE
N_MEMORY, /* The node has memory(regular, high, movable) */
#else
N_MEMORY = N_HIGH_MEMORY,
#endif
N_CPU, /* The node has one or more cpus */
NR_NODE_STATES
};nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
[N_POSSIBLE] = NODE_MASK_ALL,
[N_ONLINE] = { { [0] = 1UL } },
#ifndef CONFIG_NUMA
[N_NORMAL_MEMORY] = { { [0] = 1UL } },
#ifdef CONFIG_HIGHMEM
[N_HIGH_MEMORY] = { { [0] = 1UL } },
#endif
#ifdef CONFIG_MOVABLE_NODE
[N_MEMORY] = { { [0] = 1UL } },
#endif
[N_CPU] = { { [0] = 1UL } },
#endif /* NUMA */
};
EXPORT_SYMBOL(node_states);- N_POSSIBLE, N_ONLINE和N_CPU用於CPU和內存的熱插拔
- N_NORMAL_MEMORY， N_HIGH_MEMORY用於普通內存管理
- N_MEMORY表示有物理內存的結點
static inline int node_state(int node, enum node_states state)
{
return node_isset(node, node_states[state]);
}
static inline void node_set_state(int node, enum node_states state)
{
__node_set(node, &node_states[state]);
}
static inline void node_clear_state(int node, enum node_states state)
{
__node_clear(node, &node_states[state]);
}
static inline int num_node_state(enum node_states state)
{
return nodes_weight(node_states[state]);
}3 查找內存結點
內存結點的實例爲node_data[MAX_NUMNODES]，定義在arch/x86/mm/numa.c#L26struct pglist_data *node_data[MAX_NUMNODES] __read_mostly;
EXPORT_SYMBOL(node_data);內存結點最大數目由MAX_NUMNODES決定，定義在include/linux/numa.h#L11
#ifdef CONFIG_NODES_SHIFT
#define NODES_SHIFT CONFIG_NODES_SHIFT
#else
#define NODES_SHIFT 0
#define MAX_NUMNODES (1 << NODES_SHIFT)
#endif#define NODE_DATA(nid) (node_data[nid])3.1 查找node id
宏first_online_node用於得到第一個online的node，定義在include/linux/nodemask.h#L430#define first_online_node first_node(node_states[N_ONLINE])#define first_memory_node first_node(node_states[N_MEMORY])#define next_node(n, src) __next_node((n), &(src))
static inline int __next_node(int n, const nodemask_t *srcp)
{
return min_t(int,MAX_NUMNODES,find_next_bit(srcp->bits, MAX_NUMNODES, n+1));
}static inline int next_online_node(int nid)
{
return next_node(nid, node_states[N_ONLINE]);
}static inline int next_memory_node(int nid)
{
return next_node(nid, node_states[N_MEMORY]);
}3.2 node id的遍歷
宏for_each_node_state(__node, __state)用來遍歷處於特定狀態的所有結點，定義在include/linux/nodemask.h#L427#define for_each_node_state(__node, __state) \
for_each_node_mask((__node), node_states[__state])#define for_each_node(node) for_each_node_state(node, N_POSSIBLE)#define for_each_online_node(node) for_each_node_state(node, N_ONLINE)3.3 查找pg_data_t結構
函數first_online_pgdat得到第一個online的pg_data結構的指針，定義在mm/mmzone.c#L12struct pglist_data *first_online_pgdat(void)
{
return NODE_DATA(first_online_node);
}struct pglist_data *next_online_pgdat(struct pglist_data *pgdat)
{
int nid = next_online_node(pgdat->node_id);
if (nid == MAX_NUMNODES)
return NULL;
return NODE_DATA(nid);
}3.4 pg_data_t結構的遍歷
宏for_each_online_pgdat(pgdat)用來遍歷所有online的pg_data_t結構指針，定義在include/linux/mmzone.h#L908#define for_each_online_pgdat(pgdat) \
for (pgdat = first_online_pgdat(); \
pgdat; \
pgdat = next_online_pgdat(pgdat))