關于這個問題，意義雖然有限因為一般來說在復制文件的時候，實際的瓶頸來自于I/O，不管開啟多少個線程實際上速度并不會快多少，但是為了練習多線程編程，
這里給出了一種C++代碼實現的方式，代碼附在最后。

實際上就是將一個文件分割為多個片段，開啟多個線程進行同時復制，如果用戶制定的并行大于服務器實際的CPU核數，程序會自動降級并行度為CPU核數，如果文件小于
100M則并行度始終為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!!

復制完成后進行md5驗證
root@bogon:/home/gaopeng/mmm# md5sum log.log
f64acc21f7187a865938b340b3eda198 ?log.log
root@bogon:/home/gaopeng/mmm# md5sum log10.log
f64acc21f7187a865938b340b3eda198 ?log10.log
可以看出校驗是通過的

代碼如下：

點擊(此處)折疊或打開

#include<iostream>

#include <map>

#include<stdint.h>

#include<stdio.h>

#include<string.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/stat.h>

#include <sys/sysinfo.h>

#include<fcntl.h>

#include<errno.h>

#include <time.h>

#include <stdarg.h>

#include <stdlib.h>

#include <pthread.h>

#define MAX_BUFFER 65536

using namespace std;

pthread_mutex_t counter_mutex = PTHREAD_MUTEX_INITIALIZER;

class thread_info

{

????????private:

????????????????uint64_t start_pos;

????????????????uint64_t end_pos;

????????????????int fdr;

????????????????int fdw;

????????public:

????????????????pthread_t t_id;

????????????????static int do_id;

????????public:

????????????????thread_info()

????????????????{

????????????????????????start_pos = 0;

????????????????????????end_pos = 0;

????????????????????????fdr = 0;

????????????????????????fdw = 0;

????????????????????????t_id = 0;

????????????????}

????????????????void set_start(uint64_t a)

????????????????{

????????????????????????start_pos = a;

????????????????}

????????????????void set_end(uint64_t a)

????????????????{

????????????????????????end_pos = a;

????????????????}

????????????????void set_fd(int a,int b)

????????????????{

????????????????????????fdr = a;

????????????????????????fdw = b;

????????????????}

????????????????uint64_t get_start(void)

????????????????{

????????????????????????return start_pos;

????????????????}

????????????????uint64_t get_stop(void)

????????????????{

????????????????????????return end_pos;

????????????????}

????????????????int get_fdr(void)

????????????????{

????????????????????????return fdr;

????????????????}

????????????????int get_fdw(void)

????????????????{

????????????????????????return fdw;

????????????????}

????????????????void print(void)

????????????????{

????????????????????????cout<<start_pos<<":"<<end_pos<<":"<<t_id<<endl;

????????????????}

};

int thread_info::do_id = 0;

class ABS_dispatch

{

????????public:

????????????????ABS_dispatch()

????????????????{

????????????????????????par_thr = 0;

????????????????????????max_cpu = 0;

????????????????}

????????????????virtual thread_info* call_thread(void) = 0;

????????????????virtual void make_init(uint32_t t_n) = 0;

????????????????uint32_t getcpu(void)

????????????????{

????????????????????????return get_nprocs() ;

????????????????}

????????????????virtual ~ABS_dispatch(){

????????????????}

????????protected:

????????????????uint32_t par_thr;

????????????????uint32_t max_cpu;

};

class dispatch:public ABS_dispatch

{

????????public:

????????????????typedef multimap<uint64_t,uint64_t>::iterator pair_piece_iterator;

????????????????dispatch():ABS_dispatch()

????????{

????????????????file_idr = 0;

????????????????file_idw = 0;

????????????????file_size = 0;

????????????????tread_arr_p = NULL;

????????}

????????????????virtual thread_info* call_thread(void);

????????????????virtual void make_init(uint32_t t_n)

????????????????{

????????????????????????max_cpu = getcpu(); //

????????????????????????cout<<"Your cpu core is:"<<max_cpu<<"\n";

????????????????????????if(t_n > max_cpu) //parallel

????????????????????????{

????????????????????????????????cout<<"Parallel downgrad to cpu core:"<<max_cpu<<"\n";

????????????????????????????????par_thr = max_cpu;

????????????????????????}

????????????????????????else

????????????????????????{

????????????????????????????????par_thr = t_n;

????????????????????????}

????????????????}

????????????????void set_init(int file_idr,int file_idw)

????????????????{

????????????????????????file_size = lseek(file_idr,0,SEEK_END);

????????????????????????if(file_size<100000000)

????????????????????????{

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

????????????????????????????????par_thr = 1;

????????????????????????}

????????????????????????this->file_idr = file_idr;

????????????????????????this->file_idw = file_idw;

????????????????}

????????????????uint32_t real_par()

????????????????{

????????????????????????return par_thr;

????????????????}

????????????????virtual ~dispatch()

????????????????{

????????????????????????pair_piece.clear();

????????????????????????delete [] tread_arr_p;

????????????????}

????????private:

????????????????int file_idr;

????????????????int file_idw;

????????????????multimap<uint64_t,uint64_t> pair_piece;

????????????????uint64_t file_size;

????????public:

????????????????thread_info* tread_arr_p;

};

static void* do_work(void* argc)

{

????????uint64_t b;

????????uint64_t e;

????????int fdr;

????????int fdw;

????????char* buffer[MAX_BUFFER]={0};

????????thread_info* tread_arr_p;

????????uint64_t loopc = 0;

????????uint64_t loopc25 = 0;

????????uint64_t i = 0;

????????int m = 1;

????????pthread_t t_id;

????????tread_arr_p = static_cast<thread_info*>(argc);

????????//臨界區 MUTEX

????????pthread_mutex_lock(&counter_mutex);

????????b = (tread_arr_p+ tread_arr_p->do_id)->get_start();

????????e = (tread_arr_p+ tread_arr_p->do_id)->get_stop();

????????fdr = (tread_arr_p+ tread_arr_p->do_id)->get_fdr();

????????fdw = (tread_arr_p+ tread_arr_p->do_id)->get_fdw();

????????t_id = (tread_arr_p+ tread_arr_p->do_id)->t_id ;

????????cout<< t_id <<":"<<b<<":"<<e<<":"<<fdr<<":"<<fdw<<"\n";

????????tread_arr_p->do_id++;

????????pthread_mutex_unlock(&counter_mutex);

????????//臨界區

????????loopc = e/uint64_t(MAX_BUFFER);

????????loopc25 = loopc/(uint64_t)4;

????????while(i<loopc)

????????{

????????????????if(i == loopc25*m )

????????????????{

????????????????????????cout<< "Copy Thread:"<<t_id<<" work "<<25*m<<"%\n";

????????????????????????m++;

????????????????}

????????????????memset(buffer,0,MAX_BUFFER);

????????????????pread(fdr,buffer,MAX_BUFFER,uint64_t(i*MAX_BUFFER));

????????????????pwrite(fdw,buffer,MAX_BUFFER,uint64_t(i*MAX_BUFFER));

????????????????i++;

????????}

????????memset(buffer,0,MAX_BUFFER);

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

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

????????cout<< "Copy Thread:"<<t_id<<" work Ok!!"<<"\n";

????????return NULL;

}

thread_info* dispatch::call_thread()

{

????????int i = 0;

????????uint64_t temp_size = 0;

????????temp_size = file_size/par_thr;

????????tread_arr_p = new thread_info[par_thr];

????????cout<<"Will Create "<<par_thr<<" Threads\n";

????????//cout<<tread_arr_p<<endl;

????????//cout<<sizeof(thread_info)<<endl;

????????for(i = 0;i<par_thr-1;i++)

????????{

????????????????pair_piece.insert( pair<uint64_t,uint64_t>(temp_size*i,temp_size*(i+1)-1 ));

????????}

????????pair_piece.insert( pair<uint64_t,uint64_t>(temp_size*i,file_size ));

????????i = 1;

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

????????{

????????????????//cout<<"--Thread: "<<i<<"\n";

????????????????//cout<<it->first<<"\n";

????????????????//cout<<it->second<<"\n";

????????????????//cout<<tread_arr_p+(i-1)<<endl;

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

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

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

????????????????pthread_create(&((tread_arr_p+(i-1))->t_id),NULL,do_work,static_cast<void*>(tread_arr_p));

????????????????//(tread_arr_p+(i-1))->print();

????????????????i++;

????????}

????????return tread_arr_p;

}

int main(int argc,char** argv)

{

????????dispatch test;

????????thread_info* thread_info_p = NULL;

????????uint32_t real_par;

????????void *tret;

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

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

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

????????if(argc<4)

????????{

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

????????????????return -1;

????????}

????????if(fdr == -1 || fdw == -1)

????????{

????????????????perror("open readfile:");

????????????????return -1;

????????}

????????if(fdw == -1)

????????{

????????????????perror("open wirtefile:");

????????????????return -1;

????????}

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

????????{

????????????????perror("sscanf:");

????????????????return -1;

????????}

????????cout<<"set parallel:"<<real_par<<"\n";

????????//cout<<lseek(fd,0,SEEK_SET) <<endl;

????????test.make_init(real_par);

????????test.set_init(fdr,fdw);

????????real_par = test.real_par();

????????cout<<"real parallel:" <<real_par<<"\n";

????????thread_info_p = test.call_thread();

????????for(int i = 0 ;i<real_par;i++)

????????{

????????????????//cout<<(thread_info_p+i)->t_id<<endl;

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

????????????????//cout<<reinterpret_cast<long>(tret)<<endl;

????????}

????????close(fdw);

????????close(fdr);

}

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