为什么munmap（）函数在IOS中比在Linux上花费更多的时间？

Question

我已经在代码中映射了70M并将其复制，在Linux系统（centos）中它仅花费10ms，而在IOS中则花费1000〜2000ms（iphone 7P 64GB，iphone 6）。 munmap（）中的Linux和IOS之间有什么不同？什么情况会导致munmap（）变慢？

size_t dataLength;

void * dataPtr;

size_t dataReadLength;

void * dataReadPtr;

printf("start mmap \n");

FILE *dfile = fopen(destfile, "wb");

long dfilelen = getFileSize(sourcefile);

fseek(dfile, dfilelen - 1, 0);

// append the null to the dfile

fwrite("0", 1, 1, dfile);

fclose(dfile);


int ierr_dest = MapFileNew(destfile, &dataPtr, &dataLength, O_RDWR);
int ierr_source = MapFileNew(sourcefile, &dataReadPtr, &dataReadLength, O_RDONLY);

memcpy((char *)dataPtr, (char *)dataReadPtr, dfilelen);

StartTime = getTime();

munmap(dataReadPtr, dataLength);

iEndTime = getTime();

printf("the munmap read cost time is %d,dataLength is %d \n",iEndTime - iStartTime, dataLength);



iStartTime = getTime();

msync((void *)dataPtr, dataLength, MS_SYNC);
// this cost long time in the IOS
munmap(dataPtr, dataLength);

iEndTime = getTime();

printf("the munmap write cost time is %d,dataLength is %d \n",iEndTime - iStartTime, dataLength);