q2.c

#include <windows.h>
#include <stdio.h>
#include <string.h>

#define BUF_SIZE (128*1024)
DWORD __stdcall thread_proc(void* num);

HANDLE signal_event;

int main() {
  LARGE_INTEGER prev, next;
  BOOL r;
  QueryPerformanceCounter(&prev);
  QueryPerformanceFrequency(&next);
  printf("Initial: %lld, freq: %lld\n", prev.QuadPart, next.QuadPart);
  signal_event = CreateEvent(NULL, FALSE, FALSE, NULL);
  for (int i = 0; i<64; ++i) {
    CreateThread(NULL, 0, thread_proc, (void*)i, 0, NULL);
  }
  for (unsigned tick = 0;;++tick) {
    WaitForSingleObject(signal_event, INFINITE);
    r = QueryPerformanceCounter(&next);
    if (next.QuadPart < prev.QuadPart) {
      printf("%d %lld %lld\n", r, next.QuadPart, prev.QuadPart);
    }
    if (tick % 65536 == 0) {
      printf("still running..\n");
    }
    prev = next;
  }
}

DWORD __stdcall thread_proc(void* num) {
  char file_name[256];
  char buffer[BUF_SIZE];
  memset(buffer, 'z', BUF_SIZE);
  sprintf(file_name, "file%d", (int)num);
  for(;;) {
    HANDLE file = CreateFile(file_name,
                             GENERIC_WRITE,
                             FILE_SHARE_READ | FILE_SHARE_WRITE,
                             NULL,
                             CREATE_ALWAYS,
                             FILE_ATTRIBUTE_NORMAL,
                             NULL);
    DWORD total_bytes = 0, bytes = 0;
    while (total_bytes < BUF_SIZE) {
      WriteFile(file, buffer + total_bytes, BUF_SIZE - total_bytes, &bytes, NULL);
      total_bytes += bytes;
    }
    CloseHandle(file);
    SetEvent(signal_event);
    file = CreateFile(file_name,
                      GENERIC_READ,
                      FILE_SHARE_READ | FILE_SHARE_WRITE,
                      NULL,
                      OPEN_EXISTING,
                      FILE_ATTRIBUTE_NORMAL,
                      NULL);
    total_bytes = 0;
    bytes = 0;
    while (total_bytes < BUF_SIZE) {
      ReadFile(file, buffer + total_bytes, BUF_SIZE - total_bytes, &bytes, NULL);
      total_bytes += bytes;
    }
    CloseHandle(file);
    SetEvent(signal_event);
  }
}