Slow file IO on larger sized file.
I have the following codes to open a host file, write one line at the beginning of the file then close this file. It performed much slower on a large file (175,000 bytes) than on a small file (35 bytes). The time spent mostly on the CloseHandle() system call. Does anyone have the same problem? Is it a Microsoft Windows's bug? Any response is appreciated. // filetest.c : Testing performance of file IO in Widnows. // #include <Windows.h> #include <stdio.h> #include <string.h> char *data = "The line to be put in messages.log\n"; int logtofile(char *filename, char *buf, int siz) { int j; /* timeout */ int nw; HANDLE han; j = 10; do { DWORD lasterror; han = CreateFileA(filename,GENERIC_WRITE, FILE_SHARE_READ,NULL, OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL); lasterror = GetLastError(); if (han == INVALID_HANDLE_VALUE) { if (lasterror == ERROR_SHARING_VIOLATION) Sleep(5); else { printf("\n CreatFile Failed error=%d",lasterror); return 0; } } } while ((han == INVALID_HANDLE_VALUE) && --j); if (han != INVALID_HANDLE_VALUE) { j = WriteFile(han,buf,siz,&nw,NULL); if (!j) { printf("\nlogtofile error=%d",GetLastError()); } } j = CloseHandle(han); return 0; } int main(int argc, char* argv[]) { char *nam; int iter, i, len, msec; time_t sec; int msec; struct timeb starttimeb, endtimeb; if (argc == 1) { printf("usage: filetest <fname> [iteration] "); return 0; } nam = argv[1]; len = strlen(data); if (argc > 2) iter = atol(argv[2]); else iter = 5000; ftime(&starttimeb); for (i = 0; i < iter; i++) { logtofile(nam,data,len); } ftime(&endtimeb); sec = endtimeb.time - starttimeb.time; if (endtimeb.millitm < starttimeb.millitm) { sec--; msec = endtimeb.millitm + 1000 - starttimeb.millitm; } else { msec = endtimeb.millitm - starttimeb.millitm; } printf("\nSecond: %lld, millisecond: %d\n",sec,msec); return 0; }