{"id":3785,"date":"2012-03-12T17:32:59","date_gmt":"2012-03-12T09:32:59","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=3785"},"modified":"2012-03-15T15:12:02","modified_gmt":"2012-03-15T07:12:02","slug":"%e4%bc%99%e4%bc%b4%e7%ae%97%e6%b3%95%e7%9a%84%e5%ae%9e%e7%8e%b0-%e9%87%8a%e6%94%be%e9%a1%b5%e6%a1%86","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/3785","title":{"rendered":"\u4f19\u4f34\u7b97\u6cd5\u7684\u5b9e\u73b0-\u91ca\u653e\u9875\u6846"},"content":{"rendered":"

\u4e0e\u9875\u6846\u5206\u914d\u51fd\u6570\u7684\u6574\u4e2a\u5b9e\u73b0\u8fc7\u7a0b\u76f8\u6bd4\uff0c\u9875\u6846\u91ca\u653e\u51fd\u6570\u7684\u5b9e\u73b0\u8981\u7b80\u5355\u7684\u591a\u3002\u5e38\u7528\u7684\u9875\u6846\u5206\u914d\u51fd\u6570\u63a5\u53e3\u6709 __free_pages()\u548c__free_page()\uff0c\u5f88\u660e\u663e\u540e\u8005\u662f\u524d\u8005\u7684\u7279\u6b8a\u60c5\u51b5\u3002<\/p>\n

#define __free_page(page) __free_pages((page), 0)\r\n\r\nvoid __free_pages(struct page *page, unsigned int order)\r\n{\r\n        if (put_page_testzero(page)) {\r\n                if (order == 0)\r\n                        free_hot_cold_page(page, 0);\r\n                else\r\n                        __free_pages_ok(page, order);\r\n        }\r\n}<\/pre>\n
\u91ca\u653e\u9875\u6846\u51fd\u6570\u5728\u4e00\u5f00\u59cb\u4e5f\u5175\u5206\u4e24\u8def\uff1a\u5982\u679c\u5206\u914d\u9636\u4e3a0\uff0c\u90a3\u4e48\u76f4\u63a5\u901a\u8fc7per-CPU\u673a\u5236\u6765\u91ca\u653e\u5355\u4e00\u9875\u6846\uff1b\u5426\u5219\u901a\u8fc7__free_pages_ok()\u91ca\u653e\u6240\u7533\u8bf7\u7684\u9875\u6846\u5757\u3002<\/p>\n
1.__free_pages_ok()<\/h3>\n
\u8be5\u51fd\u6570\u5185\u90e8\u7ecf\u8fc7\u4e00\u4e9b\u68c0\u67e5\uff0c\u8fd9\u4e9b\u68c0\u67e5\u662f\u786e\u4fdd\u7a0d\u5019\u5bf9\u9875\u6846\u7684\u91ca\u653e\u662f\u5b89\u5168\u7684\uff0c\u6700\u7ec8\u4f1a\u8c03\u7528free_one_page()\uff0c\u800c\u5b83\u5185\u90e8\u53c8\u5c01\u88c5\u4e86__free_one_page()\u3002\u5185\u6838\u4e2d\u51fd\u6570\u4e4b\u95f4\u7684\u8fd9\u79cd\u591a\u6b21\u5c01\u88c5\u662f\u5f88\u5e38\u89c1\u7684\uff0c\u4e0a\u5c42\u51fd\u6570\u901a\u8fc7\u8fd9\u79cd\u5c01\u88c5\u53ef\u4ee5\u5c4f\u853d\u67d0\u4e9b\u53c2\u6570\uff0c\u800c\u5e95\u5c42\u7684\u88ab\u5c01\u88c5\u7684\u51fd\u6570\u4e5f\u53ef\u4ee5\u88ab\u591a\u79cd\u60c5\u51b5\u6240\u5f15\u7528\u3002<\/p>\n
static void __free_pages_ok(struct page *page, unsigned int order)\r\n{\r\n        \u2026\u2026\u2026\u2026\r\n        free_one_page(page_zone(page), page, order, get_pageblock_migratetype(page));\r\n        \u2026\u2026\u2026\u2026\r\n}\r\n\r\nstatic void free_one_page(struct zone *zone, struct page *page, int order,int migratetype)\r\n{\r\n        spin_lock(&zone->lock);\r\n        zone->all_unreclaimable = 0;\r\n        zone->pages_scanned = 0;\r\n\r\n        __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);\r\n        __free_one_page(page, zone, order, migratetype);\r\n        spin_unlock(&zone->lock);\r\n}<\/pre>\n
\u5728\u8c03\u7528\u6838\u5fc3\u51fd\u6570__free_one_page()\u4e4b\u524d\uff0c\u8fd8\u9700\u66f4\u65b0\u5f53\u524d\u5185\u5b58\u7ba1\u7406\u533a\u7684\u7a7a\u95f2\u9875\u9762\u6570\uff0c\u5176\u5b9e\u5c31\u662f\u5c06(1<vm_stat[NR_FREE_PAGES]\u4e0a\uff0c\u5176\u4e2dvm_stat\u662f\u4e00\u4e2a\u5bf9\u5185\u5b58\u533a\u8fdb\u884c\u4fe1\u606f\u7edf\u8ba1\u7684\u6570\u7ec4\u3002<\/p>\n
2.__free_one_page()<\/h3>\n
\u8be5\u51fd\u6570\u6309\u7167\u4f19\u4f34\u7b97\u6cd5\u7684\u56de\u6536\u539f\u7406\u5b9e\u73b0\uff0c\u4ece\u6240\u8bf7\u6c42\u7684\u5206\u914d\u9636order\u5f00\u59cb\uff0c\u4e3a\u5f53\u524d\u9875\u6846\u5757\u5c3d\u53ef\u80fd\u7684\u5bfb\u627e\u4f19\u4f34\uff0c\u8fdb\u800c\u5408\u5e76\u6210\u66f4\u5927\u7684\u9875\u6846\u5757\u3002\u5728\u8fdb\u5165\u5faa\u73af\u4e4b\u524d\uff0c\u5148\u5f97\u5230\u91ca\u653e\u9875\u6846\u5757\u7684\u7d22\u5f15page_idx\u3002<\/p>\n
\r\nstatic inline void __free_one_page(struct page *page,\r\n                struct zone *zone, unsigned int order,\r\n                int migratetype)\r\n{\r\n        unsigned long page_idx;\r\n\r\n        if (unlikely(PageCompound(page)))\r\n                if (unlikely(destroy_compound_page(page, order)))\r\n                        return;\r\n\r\n        VM_BUG_ON(migratetype == -1);\r\n\r\n        page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);\r\n\r\n        VM_BUG_ON(page_idx & ((1 << order) - 1));\r\n        VM_BUG_ON(bad_range(zone, page));\r\n\r\n        while (order < MAX_ORDER-1) {\r\n                unsigned long combined_idx;\r\n                struct page *buddy;\r\n\r\n                buddy = __page_find_buddy(page, page_idx, order);\r\n                if (!page_is_buddy(page, buddy, order))\r\n                        break;\r\n\r\n                list_del(&buddy->lru);\r\n                zone->free_area[order].nr_free--;\r\n                rmv_page_order(buddy);\r\n                combined_idx = __find_combined_index(page_idx, order);\r\n                page = page + (combined_idx - page_idx);\r\n                page_idx = combined_idx;\r\n                order++;\r\n        }\r\n        set_page_order(page, order);\r\n        list_add(&page->lru,\r\n                &zone->free_area[order].free_list[migratetype]);\r\n        zone->free_area[order].nr_free++;\r\n}\r\n<\/pre>\n
\u5728\u6bcf\u6b21\u7684\u904d\u5386\u8fc7\u7a0b\u4e2d\uff0c\u901a\u8fc7__page_find_buddy()\u4e3a\u5f53\u524d\u9875\u6846\u5757\u627e\u4e00\u4e2a\u4f19\u4f34buddy\uff0c\u8fd9\u4e2a\u4f19\u4f34\u53ef\u80fd\u5728\u5f53\u524d\u9875\u6846\u5757\u4e4b\u524d\uff0c\u4e5f\u53ef\u80fd\u5728\u5176\u4e4b\u540e\u3002\u901a\u8fc7page_is_buddy()\u5224\u65ad\u521a\u624d\u627e\u5230\u7684buddy\u662f\u5426\u80fd\u548c\u6b32\u91ca\u653e\u7684\u9875\u6846\u5757\u8fdb\u884c\u5408\u5e76\u3002\u5982\u679c\u53ef\u4ee5\u5408\u5e76\uff0c\u5219\u5c06\u8fd9\u4e2abuddy\u4ece\u5b83\u6240\u5904\u7684\u9875\u6846\u5757\u94fe\u8868\u4e2d\u5220\u9664\uff0c\u5e76\u66f4\u65b0nr_free\u7684\u503c\uff0c\u7136\u540e\u518d\u901a\u8fc7rmv_page_order()\u66f4\u65b0buddy\u9875\u6846\u5757\u9996\u9875\u6846\u7684\u76f8\u5173\u6807\u5fd7\u3002<\/p>\n
\u63a5\u4e0b\u6765\uff0c\u901a\u8fc7__find_combined_index()\u5bfb\u627e\u5408\u5e76\u540e\u9875\u6846\u5757\u7684\u7d22\u5f15combined_idx\u3002\u7531\u4e8epage\u6c38\u8fdc\u90fd\u6307\u5411\u8981\u91ca\u653e\u9875\u6846\u5757\u7684\u9996\u9875\u6846\u63cf\u8ff0\u7b26\uff0c\u56e0\u6b64\u6839\u636ecombined_idx\u66f4\u65b0page\u548cpage_idx\u3002\u540c\u65f6\uff0c\u7531\u4e8e\u6210\u529f\u8fdb\u884c\u4e86\u4f19\u4f34\u5408\u5e76\uff0c\u56e0\u6b64\u6700\u540e\u518d\u5c06\u5206\u914d\u9636order\u52a0\u4e00\u3002\u4e00\u65e6\u6ca1\u6709\u53ef\u5408\u5e76\u7684\u4f19\u4f34\uff08\u901a\u8fc7page_is_buddy()\u800cbreak\uff09\uff0c\u6574\u4e2a\u5408\u5e76\u8fc7\u7a0b\u4e5f\u5c06\u7ed3\u675f\uff0c\u5373\u9000\u51fa\u5faa\u73af\u3002<\/p>\n
\u63a5\u4e0b\u6765\u5c31\u8981\u5c06\u9875\u6846\u5757\u8fdb\u884c\u91ca\u653e\uff0c\u5176\u5b9e\u5c31\u662f\u5c06\u5408\u5e76\u540e\u7684\u9875\u6846\u5757\uff08\u4e5f\u8bb8\u5e76\u6ca1\u6709\u5408\u5e76\uff0c\u8fd8\u662f\u5408\u5e76\u4e4b\u524d\u7684\u90a3\u4e2a\u9875\u6846\u5757\uff09\u63d2\u5165\u5230\u5177\u4f53\u7684\u5206\u914d\u9636\u94fe\u8868\u4e2d\uff0c\u5e76\u8bbe\u7f6e\u9996\u9875\u6846\u7684\u76f8\u5173\u6807\u5fd7\uff0c\u5c06nr_free\u52a0\u4e00\u3002\u8981\u91ca\u653e\u7684\u9875\u6846\u5757\u7531page\u6307\u5b9a\uff0corder\u5219\u6307\u660e\u4e86\u5e94\u8be5\u5c06\u8fd9\u4e2a\u9875\u6846\u5757\u63d2\u5165\u5230\u54ea\u4e00\u4e2a\u9875\u6846\u5757\u94fe\u8868\u4e2d\uff0c\u800cmigratetype\u5219\u66f4\u5177\u4f53\u7684\u6307\u660e\u4e86\u8981\u5c06\u8be5\u9875\u6846\u5757\u63d2\u5165\u54ea\u4e00\u4e2a\u8fc1\u79fb\u5217\u8868\u4e2d\u3002\u8fd9\u4e9b\u64cd\u4f5c\u548c\u4e4b\u524d\u4f19\u4f34\u7b97\u6cd5\u4e2d\u9875\u6846\u5206\u914d\u7684\u8fc7\u7a0b\u662f\u76f8\u53cd\u7684\u3002<\/p>\n
3.__page_find_buddy()<\/h3>\n
\u524d\u6587\u5df2\u7ecf\u8bf4\u8fc7\uff0c\u8fd9\u4e2a\u51fd\u6570\u7528\u4e8e\u5bfb\u627e\u5f53\u524d\u8981\u91ca\u653e\u9875\u6846\u5757\u7684\u4f19\u4f34\u3002\u5177\u4f53\u7684\u529e\u6cd5\u662f\u5148\u901a\u8fc7\u5f02\u6216\u6c42\u51fa\u4f19\u4f34\u7684\u7d22\u5f15\uff0c\u518d\u6839\u636e\u6b64\u7d22\u5f15\u6c42\u51fa\u4f19\u4f34\u9875\u6846\u5757\u7684\u9996\u9875\u6846\u63cf\u8ff0\u7b26\u3002<\/p>\n
static inline struct page *\r\n__page_find_buddy(struct page *page, unsigned long page_idx, unsigned int order)\r\n{\r\n        unsigned long buddy_idx = page_idx ^ (1 << order);\r\n\r\n        return page + (buddy_idx - page_idx);\r\n}<\/pre>\n
\u7531\u4e8ebuddy_idx-page_idx\u7684\u503c\u53ef\u80fd\u4e3a\u6b63\u4e5f\u53ef\u80fd\u4e3a\u8d1f\uff0c\u56e0\u6b64\u4f19\u4f34\u9875\u6846\u5757\u53ef\u80fd\u5728\u5f53\u524d\u9875\u6846\u5757\u4e4b\u524d\uff0c\u4e5f\u53ef\u80fd\u5728\u5176\u4e4b\u540e\u3002<\/p>\n
4.__find_combined_index()<\/h3>\n
\u8be5\u51fd\u6570\u53ef\u4ee5\u83b7\u5f97\u5408\u5e76\u540e\u9875\u6846\u5757\u7684\u7d22\u5f15\u3002\u5982\u679c\u4f19\u4f34\u9875\u6846\u5728\u5f53\u524d\u9875\u6846\u5757\u4e4b\u540e\uff0c\u90a3\u4e48\u8fd9\u4e2a\u51fd\u6570\u8fd4\u56de\u7684\u7d22\u5f15\u8fd8\u662f\u539f\u6765\u7684\u503cpage_idx\u3002\u5982\u679c\u4f19\u4f34\u9875\u6846\u5728\u5f53\u524d\u9875\u6846\u4e4b\u524d\uff0c\u90a3\u4e48\u5408\u5e76\u540e\u9875\u6846\u7684\u7d22\u5f15\u5176\u5b9e\u662f\u4f19\u4f34\u9875\u6846\u7684\u7d22\u5f15\u3002<\/p>\n
static inline unsigned long\r\n__find_combined_index(unsigned long page_idx, unsigned int order)\r\n{\r\n        return (page_idx & ~(1 << order));\r\n}<\/pre>\n
\u81f3\u6b64\u57fa\u4e8e\u4f19\u4f34\u7b97\u6cd5\u7684\u9875\u6846\u5206\u914d\u8fc7\u7a0b\u5b8c\u6bd5\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u4e0e\u9875\u6846\u5206\u914d\u51fd\u6570\u7684\u6574\u4e2a\u5b9e\u73b0\u8fc7\u7a0b\u76f8\u6bd4\uff0c\u9875\u6846\u91ca\u653e\u51fd\u6570\u7684\u5b9e\u73b0\u8981\u7b80\u5355\u7684\u591a\u3002\u5e38\u7528\u7684\u9875\u6846\u5206\u914d\u51fd\u6570\u63a5\u53e3\u6709 __free_pag […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[266],"tags":[407,316,302,315],"class_list":["post-3785","post","type-post","status-publish","format-standard","hentry","category-266","tag-407","tag-316","tag-302","tag-315"],"views":8135,"_links":{"self":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3785","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=3785"}],"version-history":[{"count":0,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/3785\/revisions"}],"wp:attachment":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/media?parent=3785"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/categories?post=3785"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/tags?post=3785"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}