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关于这个问题，意义虽然有限因为一般来说在复制文件的时候，实际的瓶颈来自于I/O，不管开启多少个线程实际上速度并不会快多少，但是为了练习多线程编程，
这里给出了一种C++代码实现的方式，代码附在最后。

实际上就是将一个文件分割为多个片段，开启多个线程进行同时复制，如果用户制定的并行大于服务器实际的CPU核数，程序会自动降级并行度为CPU核数，如果文件小于
100M则并行度始终为1。

root@bogon:/home/gaopeng/mmm# ./parcp log.log log10.log 2       
set parallel:2
Your cpu core is:4
real parallel:2
Will Create 2 Threads
140677902710528:0:174522367:3:4
140677894317824:174522368:349044736:3:4
Copy Thread:140677902710528 work 25%
Copy Thread:140677894317824 work 25%
Copy Thread:140677902710528 work 50%
Copy Thread:140677902710528 work 75%
Copy Thread:140677902710528 work 100%
Copy Thread:140677902710528 work Ok!!
Copy Thread:140677894317824 work 50%
Copy Thread:140677894317824 work 75%
Copy Thread:140677894317824 work Ok!!

复制完成后进行md5验证
root@bogon:/home/gaopeng/mmm# md5sum log.log
f64acc21f7187a865938b340b3eda198  log.log
root@bogon:/home/gaopeng/mmm# md5sum log10.log
f64acc21f7187a865938b340b3eda198  log10.log
可以看出校验是通过的

代码如下：

点击(此处)折叠或打开

1. #include

2. #include

3. #include

4. #include

5. #include

6. #include

7. #include

8. #include

9. #include

10. #include

11. #include

12. #include

13. #include

14. #include

15. #include

16. #define MAX_BUFFER 65536

17. using namespace std;

21. pthread_mutex_t counter_mutex = PTHREAD_MUTEX_INITIALIZER;

23. class thread_info

24. {

26.         private:

27.                 uint64_t start_pos;

28.                 uint64_t end_pos;

29.                 int fdr;

30.                 int fdw;

31.         public:

32.                 pthread_t t_id;

33.                 static int do_id;

35.         public:

36.                 thread_info()

37.                 {

39.                         start_pos = 0;

40.                         end_pos = 0;

41.                         fdr = 0;

42.                         fdw = 0;

43.                         t_id = 0;

44.                 }

45.                 void set_start(uint64_t a)

46.                 {

48.                         start_pos = a;

49.                 }

50.                 void set_end(uint64_t a)

51.                 {

53.                         end_pos = a;

54.                 }

55.                 void set_fd(int a,int b)

56.                 {

58.                         fdr = a;

59.                         fdw = b;

60.                 }

62.                 uint64_t get_start(void)

63.                 {

64.                         return start_pos;

65.                 }

66.                 uint64_t get_stop(void)

67.                 {

68.                         return end_pos;

69.                 }

70.                 int get_fdr(void)

71.                 {

72.                         return fdr;

73.                 }

74.                 int get_fdw(void)

75.                 {

76.                         return fdw;

77.                 }

79.                 void print(void)

80.                 {

81.                         cout<

82.                 }

84. };

86. int thread_info::do_id = 0;

88. class ABS_dispatch

89. {

91.         public:

92.                 ABS_dispatch()

93.                 {

95.                         par_thr = 0;

96.                         max_cpu = 0;

97.                 }

98.                 virtual thread_info* call_thread(void) = 0;

99.                 virtual void  make_init(uint32_t t_n) = 0;

100.                 uint32_t getcpu(void)

101.                 {

102.                         return get_nprocs() ;

103.                 }

104.                 virtual ~ABS_dispatch(){

105.                 }

106.         protected:

107.                 uint32_t par_thr;

108.                 uint32_t max_cpu;

109. };

111. class dispatch:public ABS_dispatch

112. {

114.         public:

115.                 typedef multimap::iterator pair_piece_iterator;

116.                 dispatch():ABS_dispatch()

117.         {

118.                 file_idr = 0;

119.                 file_idw = 0;

120.                 file_size = 0;

121.                 tread_arr_p = NULL;

122.         }

123.                 virtual thread_info* call_thread(void);

124.                 virtual void  make_init(uint32_t t_n)

125.                 {

126.                         max_cpu = getcpu(); //

127.                         cout<<"Your cpu core is:"<

128.                         if(t_n > max_cpu) //parallel

129.                         {

130.                                 cout<<"Parallel downgrad to cpu core:"<

131.                                 par_thr = max_cpu;

132.                         }

133.                         else

134.                         {

135.                                 par_thr = t_n;

136.                         }

137.                 }

138.                 void set_init(int file_idr,int file_idw)

139.                 {

141.                         file_size = lseek(file_idr,0,SEEK_END);

142.                         if(file_size<100000000)

143.                         {

144.                                 cout<<"File small than 100M par = 1" <<"\n";

145.                                 par_thr = 1;

146.                         }

147.                         this->file_idr = file_idr;

148.                         this->file_idw = file_idw;

149.                 }

150.                 uint32_t real_par()

151.                 {

152.                         return par_thr;

153.                 }

154.                 virtual ~dispatch()

155.                 {

156.                         pair_piece.clear();

157.                         delete [] tread_arr_p;

158.                 }

159.         private:

160.                 int file_idr;

161.                 int file_idw;

162.                 multimap pair_piece;

163.                 uint64_t file_size;

164.         public:

165.                 thread_info* tread_arr_p;

166. };

171. static void* do_work(void* argc)

172. {

173.         uint64_t b;

174.         uint64_t e;

175.         int fdr;

176.         int fdw;

177.         char* buffer[MAX_BUFFER]={0};

178.         thread_info* tread_arr_p;

179.         uint64_t loopc = 0;

180.         uint64_t loopc25 = 0;

181.         uint64_t i = 0;

182.         int m = 1;

183.         pthread_t t_id;

184.         tread_arr_p = static_cast(argc);

186.         //临界区 MUTEX

187.         pthread_mutex_lock(&counter_mutex);

188.         b = (tread_arr_p+ tread_arr_p->do_id)->get_start();

189.         e = (tread_arr_p+ tread_arr_p->do_id)->get_stop();

190.         fdr = (tread_arr_p+ tread_arr_p->do_id)->get_fdr();

191.         fdw = (tread_arr_p+ tread_arr_p->do_id)->get_fdw();

192.         t_id = (tread_arr_p+ tread_arr_p->do_id)->t_id ;

193.         cout<< t_id <<":"<

194.         tread_arr_p->do_id++;

195.         pthread_mutex_unlock(&counter_mutex);

196.         //临界区

197.         loopc = e/uint64_t(MAX_BUFFER);

198.         loopc25 = loopc/(uint64_t)4;

200.         while(i

201.         {

203.                 if(i == loopc25*m )

204.                 {

205.                         cout<< "Copy Thread:"<

206.                         m++;

207.                 }

209.                 memset(buffer,0,MAX_BUFFER);

210.                 pread(fdr,buffer,MAX_BUFFER,uint64_t(i*MAX_BUFFER));

211.                 pwrite(fdw,buffer,MAX_BUFFER,uint64_t(i*MAX_BUFFER));

212.                 i++;

213.         }

214.         memset(buffer,0,MAX_BUFFER);

215.         pread(fdr,buffer,(e-uint64_t(i*MAX_BUFFER)),uint64_t(i*MAX_BUFFER));

216.         pwrite(fdw,buffer,(e-uint64_t(i*MAX_BUFFER)),uint64_t(i*MAX_BUFFER));

217.         cout<< "Copy Thread:"<

218.         return NULL;

219. }

221. thread_info* dispatch::call_thread()

222. {

224.         int i = 0;

225.         uint64_t temp_size = 0;

226.         temp_size = file_size/par_thr;

227.         tread_arr_p = new thread_info[par_thr];

229.         cout<<"Will Create "<

230.         //cout<

231.         //cout<

232.         for(i = 0;i

233.         {

234.                 pair_piece.insert( pair(temp_size*i,temp_size*(i+1)-1 ));

235.         }

236.         pair_piece.insert( pair(temp_size*i,file_size ));

237.         i = 1;

238.         for(pair_piece_iterator it =pair_piece.begin();it !=pair_piece.end() ;it++)

239.         {

240.                 //cout<<"--Thread: "<

241.                 //cout<first<<"\n";

242.                 //cout<second<<"\n";

244.                 //cout<

245.                 (tread_arr_p+(i-1))->set_start(it->first);

246.                 (tread_arr_p+(i-1))->set_end(it->second);

247.                 (tread_arr_p+(i-1))->set_fd(file_idr,file_idw);

248.                 pthread_create(&((tread_arr_p+(i-1))->t_id),NULL,do_work,static_cast(tread_arr_p));

249.                 //(tread_arr_p+(i-1))->print();

250.                 i++;

251.         }

253.         return tread_arr_p;

254. }

258. int main(int argc,char** argv)

259. {

261.         dispatch test;

262.         thread_info* thread_info_p = NULL;

263.         uint32_t real_par;

264.         void *tret;

266.         int fdr = open(argv[1],O_RDONLY|O_NOFOLLOW);

267.         int fdw = open(argv[2],O_RDWR|O_CREAT|O_EXCL,0755);

268.         cout<<"Author: gaopeng QQ:22389860 Blog:http://blog.itpub.net/7728585\n";

269.         if(argc<4)

270.         {

271.                 cout<<"USAGE:parcp sourcefile destfile paralle\n";

272.                 return -1;

273.         }

274.         if(fdr == -1 || fdw == -1)

275.         {

276.                 perror("open readfile:");

277.                 return -1;

278.         }

279.         if(fdw == -1)

280.         {

281.                 perror("open wirtefile:");

282.                 return -1;

283.         }

285.         if(sscanf(argv[3],"%u",&real_par) == EOF)

286.         {

287.                 perror("sscanf:");

288.                 return -1;

289.         }

291.         cout<<"set parallel:"<

293.         //cout<

294.         test.make_init(real_par);

295.         test.set_init(fdr,fdw);

296.         real_par = test.real_par();

297.         cout<<"real parallel:" <

298.         thread_info_p = test.call_thread();

299.         for(int i = 0 ;i

300.         {

301.                 //cout<<(thread_info_p+i)->t_id<

302.                 pthread_join((thread_info_p+i)->t_id,&tret);

303.                 //cout<(tret)<

304.         }

305.         close(fdw);

306.         close(fdr);

307. }

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