{"id":3776,"date":"2012-03-07T10:31:36","date_gmt":"2012-03-07T02:31:36","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=3776"},"modified":"2012-03-07T10:37:45","modified_gmt":"2012-03-07T02:37:45","slug":"%e4%bc%99%e4%bc%b4%e7%ae%97%e6%b3%95%e7%9a%84%e5%ae%9e%e7%8e%b0-%e5%88%86%e9%85%8d%e9%a1%b5%e6%a1%86","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/3776","title":{"rendered":"\u4f19\u4f34\u7b97\u6cd5\u7684\u5b9e\u73b0-\u5206\u914d\u9875\u6846"},"content":{"rendered":"

\u5185\u6838\u4e2dalloc_pages\u7cfb\u5217\u9875\u6846\u5206\u914d\u51fd\u6570\u90fd\u662f\u57fa\u4e8e\u4f19\u4f34\u7b97\u6cd5\u5b9e\u73b0\u7684\uff0c\u8fd9\u4e9b\u51fd\u6570\u6700\u7ec8\u90fd\u4f1a\u8c03\u7528\u4f19\u4f34\u7b97\u6cd5\u7684\u5165\u53e3\u51fd\u6570buffered_rmqueue()\u3002<\/p>\n

Linux\u5185\u6838\u7ba1\u7406\u7269\u7406\u5185\u5b58\u6709\u4e09\u79cd\u65b9\u5f0f\uff0c\u5176\u4e00\u5c31\u662f\u7ecf\u5178\u7684\u4f19\u4f34\u7b97\u6cd5\u3002\u4f46\u662f\u4f19\u4f34\u7b97\u6cd5\u5206\u914d\u7269\u7406\u5185\u5b58\u7684\u57fa\u672c\u5355\u4f4d\u662f\u9875\u6846\uff0c\u56e0\u6b64\u5185\u6838\u53c8\u5f15\u5165\u4e86slab\u673a\u5236\uff0c\u57fa\u4e8e\u6b64\u673a\u5236\u5b9e\u73b0\u7684\u7269\u7406\u5185\u5b58\u5206\u914d\u5668\u53ef\u4ee5\u5feb\u901f\u6709\u6548\u7684\u5206\u914d\u5c0f\u4e8e\u9875\u6846\u7684\u7269\u7406\u5185\u5b58\uff0c\u5e76\u4e14\u53ef\u4ee5\u6709\u6548\u907f\u514d\u5185\u90e8\u788e\u7247\u3002\u53e6\u5916\uff0c\u5185\u6838\u5e38\u5e38\u4f1a\u7533\u8bf7\u5355\u4e2a\u9875\u6846\u5927\u5c0f\u7684\u7269\u7406\u5185\u5b58\uff0c\u56e0\u6b64\u5185\u6838\u53c8\u5f15\u5165\u4e86per-CPU\u673a\u5236\uff0c\u8be5\u673a\u5236\u4e13\u95e8\u7528\u4e8e\u5feb\u901f\u5206\u914d\u5355\u4e2a\u9875\u6846\u3002<\/p>\n

1.__rmqueue()<\/h3>\n

\u5176\u5b9ebuffered_rmqueue()\u51fd\u6570\u4ecd\u7136\u6ca1\u6709\u8fdb\u884c\u771f\u6b63\u7684\u9875\u6846\u5206\u914d\uff0c\u8be5\u51fd\u6570\u9996\u5148\u5224\u65ad\u5206\u914d\u9636\u662f\u5426\u4e3a0\uff0c\u5982\u679c\u662f\u5219\u542f\u7528per-CPU\u673a\u5236\u6765\u5206\u914d\u7269\u7406\u5185\u5b58\uff0c\u5426\u5219\u8c03\u7528__rmqueue\uff08\uff09\u3002<\/p>\n

static struct page *__rmqueue(struct zone *zone, unsigned int order,\r\n                                                int migratetype)\r\n{\r\n        struct page *page;\r\nretry_reserve:\r\n        page = __rmqueue_smallest(zone, order, migratetype);\r\n\r\n        if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {\r\n                page = __rmqueue_fallback(zone, order, migratetype);\r\n\r\n                if (!page) {\r\n                        migratetype = MIGRATE_RESERVE;\r\n                        goto retry_reserve;\r\n                }\r\n        }\r\n\r\n        trace_mm_page_alloc_zone_locked(page, order, migratetype);\r\n        return page;\r\n}<\/pre>\n
\u4f20\u9012\u5230\u6b64\u51fd\u6570\u4e2d\u7684zone\u8868\u793a\u4f19\u4f34\u7b97\u6cd5\u5c06\u4ece\u8be5\u5185\u5b58\u7ba1\u7406\u533a\u4e2d\u5206\u914d\u9875\u6846\uff0corder\u5373\u5206\u914d\u9636\uff0cmigratetype\u8868\u793a\u8fc1\u79fb\u7c7b\u578b\u3002\u8be5\u51fd\u6570\u9996\u9009__rmqueue_smallest()\u8fdb\u884c\u5185\u5b58\u5206\u914d\uff0c\u5982\u679c\u5728\u6307\u5b9a\u7684\u8fc1\u79fb\u7c7b\u578b\u4e0a\u5206\u914d\u5931\u8d25\u540e\uff0c\u518d\u9009\u7528\u5176\u4ed6\u5907\u7528\u7684\u8fc1\u79fb\u5217\u8868\u8fdb\u884c\u5185\u5b58\u5206\u914d\uff0c\u8be5\u8fc7\u7a0b\u901a\u8fc7__rmqueue_fallback()\u5b8c\u6210\u3002\u603b\u4e4b\u5185\u6838\u603b\u662f\u5728\u7aed\u5c3d\u5168\u529b\u4fdd\u8bc1\u6ee1\u8db3\u5206\u914d\u5185\u5b58\u7684\u8bf7\u6c42\u3002<\/p>\n
2.__rmqueue_smallest()<\/h3>\n
\u8be5\u51fd\u6570\u7684\u5b9e\u73b0\u6bd4\u8f83\u7b80\u5355\uff0c\u4ece\u5f53\u524d\u6307\u5b9a\u7684\u5206\u914d\u9636\u5230\u6700\u9ad8\u5206\u914d\u9636\u4f9d\u6b21\u8fdb\u884c\u904d\u5386\u3002\u5728\u6bcf\u6b21\u904d\u5386\u7684\u5206\u914d\u9636\u94fe\u8868\u4e2d\uff0c\u6839\u636e\u53c2\u6570migratetype\u9009\u62e9\u6b63\u786e\u7684\u8fc1\u79fb\u961f\u5217\u3002\u6839\u636e\u4ee5\u4e0a\u7684\u9650\u5b9a\u6761\u4ef6\uff0c\u5f53\u9009\u5b9a\u4e00\u4e2a\u9875\u6846\u5757\u94fe\u8868\u540e\uff0c\u53ea\u8981\u8be5\u94fe\u8868\u4e0d\u4e3a\u7a7a\uff0c\u5c31\u8bf4\u660e\u53ef\u4ee5\u5206\u914d\u8be5\u5206\u914d\u9636\u5bf9\u5e94\u7684\u9875\u6846\u5757\u3002<\/p>\n
\u4e00\u65e6\u9009\u5b9a\u5728\u5f53\u524d\u904d\u5386\u7684\u5206\u914d\u9636\u94fe\u8868\u4e0a\u5206\u914d\u9875\u6846\uff0c\u90a3\u4e48\u5c31\u901a\u8fc7list_entry\uff08\uff09\u5c06\u8be5\u9875\u6846\u5757\u4ece\u94fe\u8868\u4e0a\u79fb\u9664\u3002\u7136\u540e\u5c06\u9875\u6846\u5757\u9996\u9875\u6846\u7684PG_buddy\u6807\u5fd7\u5220\u9664\uff0c\u5220\u9664\u8be5\u6807\u5fd7\u8bf4\u660e\u5f53\u524d\u9875\u6846\u5757\u5df2\u7ecf\u4e0d\u5c5e\u4e8e\u4f19\u4f34\u94fe\u8868\u3002\u5e76\u4e14\u5c06\u8be5\u9996\u9875\u6846\u63cf\u8ff0\u7b26\u4e2d\u7684priveate\u7f6e0\uff0c\u8be5\u5b57\u6bb5\u4e2d\u672c\u6765\u4fdd\u5b58\u7684\u662f\u5176\u6240\u5904\u9875\u6846\u5757\u7684\u5206\u914d\u9636\u3002\u4ee5\u4e0a\u8fd9\u4e2a\u8fc7\u7a0b\u901a\u8fc7rmv_page_order()\u5b8c\u6210\u3002\u6b64\u5916\uff0c\u8fd8\u8981\u66f4\u65b0\u9875\u6846\u5757\u94fe\u8868nr_free\u7684\u503c\u3002<\/p>\n
static inline\r\nstruct page *__rmqueue_smallest(struct zone *zone, unsigned int order,\r\n                                                int migratetype)\r\n{\r\n        unsigned int current_order;\r\n        struct free_area * area;\r\n        struct page *page;\r\n\r\n        for (current_order = order; current_order < MAX_ORDER; ++current_order) {\r\n                area = &(zone->free_area[current_order]);\r\n                if (list_empty(&area->free_list[migratetype]))\r\n                        continue;\r\n\r\n                page = list_entry(area->free_list[migratetype].next, struct page, lru);\r\n                list_del(&page->lru);\r\n                rmv_page_order(page);\r\n                area->nr_free--;\r\n                expand(zone, page, order, current_order, area, migratetype);\r\n                return page;\r\n        }\r\n\r\n        return NULL;\r\n}\r\n\r\nstatic inline void rmv_page_order(struct page *page)\r\n{\r\n        __ClearPageBuddy(page);\r\n        set_page_private(page, 0);\r\n}<\/pre>\n
__rmqueue_smallest()\u5185\u90e8\u8fd8\u6709\u4e00\u4e2a\u91cd\u8981\u7684\u51fd\u6570expand()\u3002\u8fdb\u5165\u8be5\u51fd\u6570\u7684\u6761\u4ef6\u662f\u5f53\u6240\u7533\u8bf7\u7684\u5206\u914d\u9636order\u5c0f\u4e8e\u5f53\u524d\u9009\u4e2d\u7684\u5206\u914d\u9636current_order\uff0c\u4e5f\u5c31\u662f\u8bf4\u6307\u5b9a\u7684\u5206\u914d\u9636\u94fe\u8868\u4e2d\u6ca1\u6709\u7a7a\u95f2\u7684\u9875\u6846\u5757\uff0c\u53ea\u80fd\u9009\u7528\u8f83\u5927\u7684\u9875\u6846\u5757\u3002\u56e0\u6b64\uff0cexpand()\u5fc5\u987b\u6309\u7167\u4f19\u4f34\u7b97\u6cd5\u7684\u5206\u88c2\u539f\u7406\u5c06\u6bd4\u8f83\u5927\u7684\u9875\u6846\u5757\u5206\u5272\u6210\u8f83\u5c0f\u7684\u5757\u3002<\/p>\n
3.expand()<\/p>\n
\u5206\u88c2\u51fd\u6570\u7684\u5b9e\u73b0\u4e5f\u662f\u663e\u800c\u6613\u89c1\u7684\uff0c\u5b83\u5b8c\u5168\u9075\u7167\u4f19\u4f34\u7b97\u6cd5\u7684\u5206\u88c2\u539f\u7406\u3002\u8fd9\u91cc\u6709\u4e24\u4e2a\u5206\u914d\u9636\uff0c\u4e00\u4e2a\u662f\u7533\u8bf7\u9875\u6846\u65f6\u6307\u5b9a\u7684low\uff0c\u4e00\u4e2a\u662f\u5728\u4e0a\u7ea7\u51fd\u6570\u4e2d\u904d\u5386\u65f6\u6240\u9009\u5b9a\u7684high\u3002\u8be5\u51fd\u6570\u4ecehigh\u5206\u914d\u9636\u5f00\u59cb\u9012\u51cf\u5411low\u904d\u5386\uff0c\u4e5f\u5c31\u662f\u4ece\u8f83\u5927\u7684\u9875\u6846\u5757\u5f00\u59cb\u4f9d\u6b21\u5206\u88c2\u3002<\/p>\n
\u6bd4\u5982high\u4e3a4\uff0c\u800clow\u4e3a2\u3002\u90a3\u4e48\u7b2c\u4e00\u904d\u5386\u65f6\uff0c\u5c06\u5927\u5c0f\u4e3a16\uff08\u5206\u914d\u9636\u4e3a4\uff09\u7684\u9875\u6846\u5757\u4e00\u4efd\u4e3a2\u3002\u901a\u8fc7list_add()\u5c06\u540e\u9762\u76848\u4e2a\u8fde\u7eed\u9875\u6846\u5757\u52a0\u5165\u4e0b\u7ea7\u94fe\u8868\uff08\u5206\u914d\u9636\u4e3a3\uff09\uff0c\u4e0b\u7ea7\u94fe\u8868\u901a\u8fc7\u5c06area\u6307\u9488\u81ea\u51cf\u5373\u53ef\u5f97\u5230\uff0c\u540e8\u4e2a\u9875\u6846\u5757\u7684\u6307\u9488\u4e5f\u901a\u8fc7page+size\u83b7\u5f97\uff0c\u800cpage\u4ecd\u7136\u6307\u5411\u6700\u521d\u7684\u9875\u6846\u5757\u9996\u9875\u6846\u3002\u6b64\u65f6\u8fd8\u8981\u5bf9\u5206\u914d\u9636\u4e3a3\u7684\u94fe\u8868\u66f4\u65b0nr_free\uff0c\u4ee5\u53ca\u901a\u8fc7set_page_order()\u5bf9\u540e8\u4e2a\u9875\u6846\u5757\u8bbe\u7f6e\u4e00\u4e9b\u6807\u5fd7\u3002<\/p>\n
\u7b2c\u4e8c\u6b21\u904d\u5386\u5c06\u524d\u97628\u4e2a\u9875\u6846\u5757\u7ee7\u7eed\u4e00\u5206\u4e3a\u4e8c\uff0c\u5c06\u540e4\u4e2a\u9875\u6846\u5757\u52a0\u5165area\u6240\u6307\u5411\u7684\u4e0b\u7ea7\u94fe\u8868\uff08\u5206\u914d\u9636\u4e3a2\uff09\u3002\u7b2c\u4e09\u6b21\u904d\u5386\u65f6\uff0c\u5faa\u73af\u6761\u4ef6\u5df2\u7ecf\u4e0d\u518d\u6ee1\u8db3\uff0c\u56e0\u6b64\u8fd4\u56de\u524d4\u4e2a\u9875\u6846\u5757\u9996\u9875\u6846\u7684\u63cf\u8ff0\u7b26\u5730\u5740page\u3002<\/p>\n
static inline void expand(struct zone *zone, struct page *page,\r\n        int low, int high, struct free_area *area,\r\n        int migratetype)\r\n{\r\n        unsigned long size = 1 << high;\r\n         while (high > low) {\r\n                area--;\r\n                high--;\r\n                size >>= 1;\r\n                VM_BUG_ON(bad_range(zone, &page[size]));\r\n                list_add(&page[size].lru, &area->free_list[migratetype]);\r\n                area->nr_free++;\r\n                set_page_order(&page[size], high);\r\n        }\r\n}\r\n\r\nstatic inline void set_page_order(struct page *page, int order)\r\n{\r\n        set_page_private(page, order);\r\n        __SetPageBuddy(page);\r\n}<\/pre>\n","protected":false},"excerpt":{"rendered":"
\u5185\u6838\u4e2dalloc_pages\u7cfb\u5217\u9875\u6846\u5206\u914d\u51fd\u6570\u90fd\u662f\u57fa\u4e8e\u4f19\u4f34\u7b97\u6cd5\u5b9e\u73b0\u7684\uff0c\u8fd9\u4e9b\u51fd\u6570\u6700\u7ec8\u90fd\u4f1a\u8c03\u7528\u4f19\u4f34\u7b97\u6cd5\u7684\u5165\u53e3\u51fd\u6570bu […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-3776","post","type-post","status-publish","format-standard","hentry","category-linuxc"],"views":9672,"_links":{"self":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3776","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/comments?post=3776"}],"version-history":[{"count":0,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3776\/revisions"}],"wp:attachment":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/media?parent=3776"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/categories?post=3776"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/tags?post=3776"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}