将功能卸载到Intel Xeon Phi所需的时间

卸载调用是否需要预定义的时间将函数的数据（参数）从主机传输到Intel MIC（Xeon Phi协处理器3120系列）？

具体来说，我为我想要在MIC上执行的功能卸载调用（“#pragma offload target（mic）”） . 该函数有15个参数（指针和变量），我已经确认了MIC上参数的正确传递 . 但是我已经简化了代码，目的是检查传递参数的时间，因此它只包含一个简单的“printf（）”函数 . 我使用“sys / time.h”头文件的“gettimeofday（）”来测量时间，如下面的代码所示：

Some hardware informations for the host: 英特尔（R）酷睿（TM）i7-3770 CPU @ 3.40GHz / CentOS版本6.8 / PCI Express版本2.0

main.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/time.h>
#include <string.h>

__attribute__ (( target (mic))) unsigned long long ForSolution = 0;
__attribute__ (( target (mic))) unsigned long long sufficientSol = 1;
__attribute__ (( target (mic))) float timer = 0.0;

__attribute__ (( target (mic))) void function(float *grid, float *displ, unsigned long long *li, unsigned long long *repet, float *solution, unsigned long long dim, unsigned long long numOfa, unsigned long long numLoops, unsigned long long numBlock, unsigned long long thread, unsigned long long blockGrid, unsigned long long station, unsigned long long bytesSol, unsigned long long totalSol, volatile unsigned long long *prog);

   float    *grid, *displ, *solution;
   unsigned long long   *li,repet;
   volatile unsigned long long  *prog;
   unsigned long long dim = 10, grid_a = 3, numLoops = 2, numBlock = 0;
   unsigned long long thread = 220, blockGrid = 0, station = 12;
   unsigned long long station_at = 8, bytesSol, totalSol;

   bytesSol = dim*sizeof(float);
   totalSol = ((1024 * 1024 * 1024) / bytesSol) * bytesSol;



   /******** Some memcpy() functions here for the pointers*********/                   



gettimeofday(&start, NULL);

   #pragma offload target(mic) \
        in(grid:length(dim * grid_a * sizeof(float))) \
        in(displ:length(station * station_at * sizeof(float))) \
        in(li:length(dim * sizeof(unsigned long long))) \
        in(repet:length(dim * sizeof(unsigned long long))) \
        out(solution:length(totalSol/sizeof(float))) \
        in(dim,grid_a,numLoops,numBlock,thread,blockGrid,station,bytesSol,totalSol) \
        in(prog:length(sizeof(volatile unsigned long long))) \
        inout(ForSolution,sufficientSol,timer)
   {
        function(grid, displ, li, repet, solution, dim, grid_a, numLoops, numBlock, thread, blockGrid, station, bytesSol, totalSol, prog);
   }

    gettimeofday(&end, NULL);  

    printf("Time to tranfer data on Intel Xeon Phi: %f sec\n", (((end.tv_sec - start.tv_sec) * 1000000.0 + (end.tv_usec - start.tv_usec)) / 1000000.0) - timer);
    printf("Time for calculations: %f sec\n", timer);

function.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/time.h>
#include <string.h>
#include <omp.h>

void function(float *grid, float *displ, unsigned long long *li, unsigned long long *repet, float *solution, unsigned long long dim, unsigned long long numOfa, unsigned long long numLoops, unsigned long long numBlock, unsigned long long thread, unsigned long long blockGrid, unsigned long long station, unsigned long long bytesSol, unsigned long long totalSol, volatile unsigned long long *prog)
{
    struct timeval      timer_start, timer_end;

    gettimeofday(&timer_start, NULL);

printf("Hello World!!!\n");


    gettimeofday(&timer_end, NULL);

    timer = ((timer_end.tv_sec - timer_start.tv_sec) * 1000000.0 + (timer_end.tv_usec - timer_start.tv_usec)) / 1000000.0 ;  
}

Results of terminal:

Time to tranfer data on Intel Xeon Phi: 3.512706 sec
Time for calculations: 0.000002 sec
Hello World!!!

该代码需要3.5秒才能完成“卸载目标” . 以上结果是否正常？有没有办法减少卸载调用的显着时间延迟？