{"id":1875,"date":"2012-04-07T14:33:31","date_gmt":"2012-04-07T06:33:31","guid":{"rendered":"http:\/\/www.mudone.com\/?p=1875"},"modified":"2012-04-07T14:33:31","modified_gmt":"2012-04-07T06:33:31","slug":"repost-ring-buffer-and-memory-poll","status":"publish","type":"post","link":"https:\/\/www.mudone.com\/?p=1875","title":{"rendered":"\u8f6c\u8f7d\uff1aRing Buffer \u548c Memory Poll"},"content":{"rendered":"

\u539f\u6587\u94fe\u63a5\uff1ahttp:\/\/blog.ddup.us\/?p=241<\/a>
\n—————————————————————————-
\n\u90a3\u5929\u770b\u5230\u5fae\u535a\u4e0a\u770b\u5230\u8ba8\u8bba\u5982\u4f55\u8bbe\u8ba1\u7f51\u7edc\u7a0b\u5e8fBuffer\uff08\u94fe\u63a5\uff09\u3002\u5176\u4e2d@\u7b80\u60a6\u98ce\u4e91 \u7ed9\u51fa\u4e2a\u4f7f\u7528Ring Buffer\u7684\u601d\u8def\u540c\u65f6\u4e5f\u987a\u5e26\u7740\u5632\u8bbd\u4e86\u4e00\u4e0bC++\u548cSTL\uff08\u94fe\u63a5\uff09\uff0c\u7ed3\u679c\u5f15\u51fa\u6df7\u6218\u3002\u672c\u6587\u4e0d\u5173\u5fc3\u4e8b\u4ef6\uff0c\u7eaf\u7cb9\u8ba8\u8bba\u5176\u4e2d\u7684\u4e24\u4e2a\u6280\u672f\u70b9\u2014\u2014RingBuffer\u548cMemory Poll\u3002<\/p>\n

\u4e24\u8005\u90fd\u662f\u5185\u5b58\u7ba1\u7406\u4e2d\u6bd4\u8f83\u5e38\u7528\u7684\u6280\u672f\u3002\u6211\u4eec\u77e5\u9053C\u8bed\u8a00\u4e2d\u4f7f\u7528malloc\/free\u5e93\u51fd\u6570\u6765\u7533\u8bf7\/\u91ca\u653e\u5185\u5b58\uff0cC++\u4e2d\u5bf9\u5e94\u7684\u662fnew\/delete\uff0c\u7ec8\u5f52\u4e5f\u662f\u8c03\u7528malloc\/free\u3002\u6709\u4e9b\u7a0b\u5e8f\u4f1a\u975e\u5e38\u9891\u7e41\u7684\u7533\u8bf7\/\u91ca\u653e\u5185\u5b58\uff0c\u8fd9\u5c31\u5bfc\u81f4\u5185\u5b58\u788e\u7247\u7684\u4ea7\u751f\uff0c\u8fdb\u800c\u5f15\u8d77\u6027\u80fd\u4e0b\u964d\u751a\u81f3\u5185\u5b58\u5206\u914d\u5931\u8d25\u3002\u50cfMemcached\u8fd9\u79cd\u5185\u5b58kv\u6570\u636e\u5e93\u4e3a\u4e86\u89e3\u51b3\u8fd9\u79cd\u95ee\u9898\u90fd\u662f\u5728\u5e94\u7528\u5c42\u81ea\u5df1\u53c8\u5b9e\u73b0\u4e86\u4e00\u5957\u5185\u5b58\u7ba1\u7406\u6a21\u5757\u3002Redis\u65e9\u671f\u7248\u672c\u76f4\u63a5\u4f7f\u7528malloc\/free\u5e93\u51fd\u6570\uff0c\u540e\u6765\u5fcd\u53d7\u4e0d\u4e86\u5176\u6027\u80fd\uff0c\u5728\u540e\u7eed\u7248\u672c\u4e2d\u4f7f\u7528freebsd\u4e2d\u7684\u5185\u5b58\u7ba1\u7406\u7b97\u6cd5jemalloc\u6765\u4ee3\u66ff\u3002\u6240\u4ee5\u5728\u9ad8\u6027\u80fd\u7a0b\u5e8f\u4e2d\uff0c\u4f18\u826f\u7684\u5185\u5b58\u7ba1\u7406\u7b97\u6cd5\u81f3\u5173\u91cd\u8981\u3002<\/p>\n

Ring Buffer<\/p>\n

Ring Buffer\u4e5f\u53ebCircular Buffer\uff0c\u662f\u4e00\u79cd\u7f13\u51b2\u533a\u6570\u636e\u7ed3\u6784\uff0c\u4e00\u822c\u7528\u4e8e\u751f\u4ea7\u8005-\u6d88\u8d39\u8005\u6a21\u5f0f\u7684\u7a0b\u5e8f\u4e2d\uff0c\u4e00\u4e2a\u6216\u591a\u4e2a\u751f\u4ea7\u8005\u4e0d\u505c\u4ea7\u751f\u6570\u636e\uff0c\u540c\u65f6\u4e00\u4e2a\u6216\u591a\u4e2a\u6d88\u8d39\u8005\u4f7f\u7528\u6570\u636e\uff0c\u6570\u636e\u4f7f\u7528\u5b8c\u8fd9\u5757\u7f13\u51b2\u533a\u5c31\u53ef\u4ee5\u91ca\u653e\u4e86\u3002\u7b80\u5355\u7684Ring Buffer\u5176\u5b9e\u5c31\u662f\u57fa\u4e8e\u8fde\u7eed\u5185\u5b58\u5730\u5740\u7684\u5faa\u73af\u961f\u5217\uff0c\u7a0d\u6709\u4e0d\u540c\u7684\u662f\u5f53\u961f\u5217\u6ee1\u65f6\uff0c\u67d0\u4e9bRing Buffer\u5e94\u7528\u573a\u666f\u53ef\u4ee5\u76f4\u63a5\u8986\u76d6\u6389\u961f\u5c3e\u7684\u6570\u636e\u3002\u98ce\u4e91\u7ed9\u51fa\u7684socket\u8fde\u63a5\u4f8b\u5b50\uff08\u94fe\u63a5\uff09\u5c31\u662f\u8fd9\u79cd\u60c5\u51b5\u3002\u5efa\u7acbRing Buffer\u9996\u5148\u5c31\u662f\u5148malloc\u51fa\u4e00\u5927\u5757\u8fde\u7eed\u5185\u5b58\u7a7a\u95f4\uff0c\u7136\u540e\u9075\u5faa\u5148\u5165\u5148\u51faFIFO\u539f\u5219\u7533\u8bf7\u91ca\u653e\u5185\u5b58\uff0c\u540e\u7eed\u7684\u5185\u5b58\u64cd\u4f5c\u90fd\u5728\u8fd9\u5757\u5b9e\u73b0\u5f00\u8f9f\u7684\u5185\u5b58\u533a\u57df\u5b8c\u6210\uff0c\u8fd9\u4e5f\u5c31\u7701\u53bb\u4e86\u6bcf\u6765\u4e00\u6761\u6570\u636e\u5c31\u7533\u8bf7\u4e00\u6b21\u5185\u5b58\u7684\u5f00\u9500\u3002\u53ef\u89c1\u4e0d\u4ec5\u662f\u4ece\u6267\u884c\u65f6\u95f4\u4e0a\u8fd8\u662f\u4ece\u51cf\u5c11\u5185\u5b58\u788e\u7247\u89d2\u5ea6\u770b\uff0c\u8fd9\u79cd\u65b9\u6cd5\u90fd\u6bd4\u539f\u751f\u7684malloc\u8981\u597d\u3002<\/p>\n

\u4f46\u662f\u8fd9\u79cd\u65b9\u5f0f\u7684\u7f3a\u70b9\u4e5f\u662f\u663e\u800c\u6613\u89c1\u7684\uff1a1\uff09\u53ea\u9002\u7528\u4e8e\u6570\u636e\u662fFIFO\u7684\u8fd9\u79cd\u60c5\u51b5\uff0c\u4e00\u65e6\u6570\u636e\u4e0d\u662f\u6309\u7167\u5148\u7533\u8bf7\u5148\u91ca\u653e\u539f\u5219\u8fdb\u884c\uff0c\u90a3\u5185\u5b58\u788e\u7247\u95ee\u9898\u8fd8\u662f\u89e3\u51b3\u4e0d\u4e86\u30022\uff09\u9700\u8981\u9884\u4f30\u7f13\u51b2\u533a\u5927\u5c0f\uff0c\u56e0\u4e3a\u7f13\u51b2\u533a\u4e00\u6b21\u7533\u8bf7\u5b8c\u6bd5\uff0c\u540e\u7eed\u8c03\u6574\u4ee3\u4ef7\u6bd4\u8f83\u5927\uff0c\u6240\u4ee5\u9700\u8981\u9884\u4f30\u5927\u5c0f\u30023\uff09\u961f\u5217\u7ba1\u7406\uff0c\u8fd9\u5176\u5b9e\u662f\u6570\u636e\u7ed3\u6784\u4e0e\u7b97\u6cd5\u7684\u95ee\u9898\u3002\u4e0d\u8fc7\u4e00\u65e6\u5176\u4e2d\u5b58\u653e\u65f6\u7684\u53d8\u957f\u6570\u636e\u7684\u8bdd\uff0c\u89e3\u51b3\u8d77\u6765\u8981\u7a0d\u7a0d\u590d\u6742\u4e00\u4e9b\u3002<\/p>\n

\u6458\u4e00\u6bb5Wikipedia\u4e0a\u7684\u7b80\u5355Ring Buffer\u4ee3\u7801\uff1a<\/p>\n

\/* Circular buffer example, keeps one slot open *\/
\n#include
\n#include <\/p>\n

\/* Opaque buffer element type. This would be defined by the application. *\/
\ntypedef struct{int value;} ElemType;<\/p>\n

\/* Circular buffer object *\/
\ntypedefstruct{
\n int size; \/* maximum number of elements *\/
\n int start; \/* index of oldest element *\/
\n int end; \/* index at which to write new element *\/
\n ElemType *elems; \/* vector of elements *\/
\n} CircularBuffer;<\/p>\n

void cbInit(CircularBuffer *cb,int size){
\n cb->size = size +1;\/* include empty elem *\/
\n cb->start =0;
\n cb->end =0;
\n cb->elems =(ElemType *)calloc(cb->size,sizeof(ElemType));
\n}<\/p>\n

void cbFree(CircularBuffer *cb){
\n free(cb->elems);\/* OK if null *\/
\n}<\/p>\n

int cbIsFull(CircularBuffer *cb){
\n return(cb->end +1)% cb->size == cb->start;
\n}<\/p>\n

int cbIsEmpty(CircularBuffer *cb){
\n return cb->end == cb->start;
\n}<\/p>\n

\/* Write an element, overwriting oldest element if buffer is full. App can
\n choose to avoid the overwrite by checking cbIsFull(). *\/
\nvoid cbWrite(CircularBuffer *cb, ElemType *elem){
\n cb->elems[cb->end]=*elem;
\n cb->end =(cb->end +1)% cb->size;
\n if(cb->end == cb->start)
\n cb->start =(cb->start +1)% cb->size;\/* full, overwrite *\/
\n}<\/p>\n

\/* Read oldest element. App must ensure !cbIsEmpty() first. *\/
\nvoid cbRead(CircularBuffer *cb, ElemType *elem){
\n *elem = cb->elems[cb->start];
\n cb->start =(cb->start +1)% cb->size;
\n}<\/p>\n

int main(int argc,char**argv){
\n CircularBuffer cb;
\n ElemType elem ={0};<\/p>\n

int testBufferSize =10;\/* arbitrary size *\/
\n cbInit(&cb, testBufferSize);<\/p>\n

\/* Fill buffer with test elements 3 times *\/
\n for(elem.value=0; elem.value<3* testBufferSize;++ elem.value)\n cbWrite(&cb,&elem);\n \n \/* Remove and print all elements *\/\n while(!cbIsEmpty(&cb)){\n cbRead(&cb,&elem);\n printf(\"%d\\n\", elem.value);\n }\n \n cbFree(&cb);\n return0; \n}<\/p><\/blockquote>\n

Memory Poll<\/p>\n

\u5185\u5b58\u6c60\u6280\u672f\u66f4\u662f\u7531\u6765\u5df2\u4e45\uff0c\u4ee5\u81f3\u4e8e\u57fa\u672c\u4e0a\u9047\u5230\u5185\u5b58\u7ba1\u7406\u4e00\u822c\u4eba\u9996\u5148\u60f3\u5230\u7684\u5c31\u662f\u8fd9\u4e2a\u3002\u7684\u786e\u4e0d\u7ba1\u662f\u5728\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u4e2d\u8fd8\u662f\u5728\u5e94\u7528\u5c42\u7a0b\u5e8f\u4e2d\uff0c\u5185\u5b58\u6c60\u6280\u672f\u5e7f\u6cdb\u7684\u5e94\u7528\u3002\u4e4b\u524d\u8bf4\u7684memcached\u5c31\u662f\u81ea\u5df1\u5728\u5e94\u7528\u5c42\u5b9e\u73b0\u4e86\u4e00\u5957\u5185\u5b58\u6c60\u3002\u53e6\u5916SGI\u7248\u672c\u7684STL\u4e2d\u4e3a\u4e86\u5e94\u5bf9\u9891\u7e41\u7533\u8bf7\/\u91ca\u653e\u5c0f\u5185\u5b58\u5757\u4ea7\u751f\u7684\u5185\u5b58\u788e\u7247\u95ee\u9898\uff0c\u540c\u6837\u7528\u5230\u4e86\u5185\u5b58\u6c60\u6280\u672f\u3002<\/p>\n

SGI\u7248\u672c\u7684STL\u4e2d\u9ed8\u8ba4\u7684\u5185\u5b58\u5206\u914d\u662f\u901a\u8fc7std::alloc\u5b8c\u6210\u7684\uff0c\u5176\u4e2d\u5c06\u5185\u5b58\u5206\u914d\u5212\u5206\u4e3a\u4e24\u7ea7\uff1a\u5c0f\u4e8e\u7b49\u4e8e128B\u7684\u5728\u7b2c\u4e00\u7ea7\u4e2d\u5206\u914d\uff1b\u5927\u4e8e128B\u7684\u5728\u7b2c\u4e8c\u7ea7\u4e2d\u5206\u914d\u3002\u7b2c\u4e8c\u7ea7\u5185\u5b58\u5206\u914d\u5c31\u662f\u7b80\u5355\u7684\u8c03\u7528operator new\u5b8c\u6210\u3002\u7b2c\u4e00\u7ea7\u5b9e\u9645\u662f\u4e00\u4e2a\u5185\u5b58\u6c60\uff1a\u5176\u4e2d\u670911\u4e2aslot\uff0c\u6bcf\u4e2aslot\u5bf9\u5e94\u4e00\u4e2a\u540c\u6837\u5927\u5c0f\u7a7a\u95f2\u5757\u94fe\u8868\u3002\u5757\u4ece8B\u5f00\u59cb\uff0c\u6309\u71678B\u7684\u500d\u6570\u9012\u589e\u76f4\u5230128\u3002\u8fd9\u6837\u5728\u5206\u914d\u5c0f\u5185\u5b58\u65f6\uff0c\u663e\u793a\u5c06\u8bf7\u6c42\u7684\u5bb9\u91cf\u5411\u4e0a\u63098\u7684\u500d\u6570\u53d6\u6574\uff0c\u7136\u540e\u4ece\u7a7a\u95f2\u94fe\u8868\u4e2d\u62ff\u4e00\u4e2a\u7a7a\u95f2\u533a\u5757\u51fa\u6765\u3002\u56de\u6536\u7684\u65f6\u5019\u91c7\u7528\u7c7b\u4f3c\u7684\u65b9\u6cd5\uff0c\u5c06\u7a7a\u95f2\u5757\u5f52\u8fd8\u5230\u7a7a\u95f2\u94fe\u8868\u4e2d\u3002\u8fd9\u6837\u5c31\u80fd\u6709\u6548\u907f\u514d\u9891\u7e41\u5206\u914d\u91ca\u653e\u5c0f\u5185\u5b58\u5757\u3002<\/p>\n

\u53ef\u89c1\u5185\u5b58\u6c60\u6280\u672f\u76f8\u5bf9\u4e8e\u4e0a\u8fb9\u7684Ringbuffer\u7684\u4f18\u70b9\u662f\uff1a\u4e0d\u7528\u5173\u5fc3\u5185\u5b58\u7533\u8bf7\u91ca\u653e\u7684\u987a\u5e8f\u3002\u7f3a\u70b9\u662f\uff1a1\uff09\u6570\u636e\u7ed3\u6784\u66f4\u590d\u6742\uff1b2\uff09\u6309\u7167\u56fa\u5b9a\u5927\u5c0f\u7684\u5757\u5212\u5206\u5b58\u5728\u5185\u5b58\u6d6a\u8d39\u3002\u8fd9\u79cd\u6d6a\u8d39\u662f\u4e0d\u80fd\u907f\u514d\u7684\uff0c\u4f46\u662f\u53ef\u4ee5\u901a\u8fc7\u5408\u7406\u7684\u9009\u62e9\u5757\u7684\u5927\u5c0f\uff0c\u5c3d\u91cf\u51cf\u5c11\u6d6a\u8d39\u3002Memcached\u63d0\u4f9b\u4e86\u53ef\u4ee5\u6839\u636e\u7528\u6237\u81ea\u5b9a\u4e49\u7684\u9012\u589e\u56e0\u5b50\u8bbe\u7f6e\u95f4\u9694slot\u4e2d\u5757\u7684\u589e\u957f\u91cf\u3002\u8fd9\u6837\u5c31\u53ef\u4ee5\u9488\u5bf9\u7279\u5b9a\u4e1a\u52a1\u505a\u7279\u5b9a\u4f18\u5316\u3002<\/p>\n

\u53c2\u8003<\/p>\n

http:\/\/en.wikipedia.org\/wiki\/Circular_buffer<\/p>\n

http:\/\/blog.codingnow.com\/2012\/02\/ring_buffer.html<\/p>\n

\u300aSTL\u6e90\u7801\u8be6\u89e3\u300b<\/p>\n","protected":false},"excerpt":{"rendered":"

\u539f\u6587\u94fe\u63a5\uff1ahttp:\/\/blog.ddup.us\/?p=241 ———&# […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","footnotes":""},"categories":[9],"tags":[],"class_list":["post-1875","post","type-post","status-publish","format-standard","hentry","category-technote"],"_links":{"self":[{"href":"https:\/\/www.mudone.com\/index.php?rest_route=\/wp\/v2\/posts\/1875","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mudone.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mudone.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mudone.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mudone.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1875"}],"version-history":[{"count":1,"href":"https:\/\/www.mudone.com\/index.php?rest_route=\/wp\/v2\/posts\/1875\/revisions"}],"predecessor-version":[{"id":1876,"href":"https:\/\/www.mudone.com\/index.php?rest_route=\/wp\/v2\/posts\/1875\/revisions\/1876"}],"wp:attachment":[{"href":"https:\/\/www.mudone.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1875"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mudone.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1875"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mudone.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1875"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}