* On Mon, 14 Apr 2008, Alexander Dorofeyev wrote:
I was able to isolate it in a very small and simplistic testcase, which shows this same problem. It will be included as attachment. Holding a key and moving mouse over the window steadily increases main loop latency from 10 to 50 (and even 100) in a short time, especially so if quickly clicking both mouse buttons as well. In a game this means going from 100 fps to 20 or 10 just because of input messages.
...
Now, I do realize that what the testcase is doing is bad practice, it's basically refusing to process certain types of messages, and PeekMessage just once during a loop is probably bad as well, but that's what the game was originally doing in its main game loop. They do plan to fix it in the game. Still, there are several concerns about it:
- No slowdown happens of Windows as far as I can tell. No matter how
much I move the mouse holding key and clicking madly, it shows same stable 15-16 ticks latency in the testcase. I don't know what it does, but somehow it handles this situation better than Wine.
I am not minded in this area, Alexander (an am a bit away in time), but is it algorithmically possible to convert this code to somewhat reliable test case which wouln't depend on CPU perfomance(s) (by any chance)?
#include <windows.h>
HWND window;
int PASCAL WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { WNDCLASS wc = {0}; MSG msg; DWORD ticks, ticks2; HHOOK kbd_hook, mouse_hook;
wc.lpfnWndProc = &DefWindowProc; wc.lpszClassName = "testwc"; RegisterClass(&wc); window = CreateWindow("testwc", "test", WS_OVERLAPPED | WS_VISIBLE | WS_CAPTION , 0, 0, 640, 480, 0, 0, 0, 0);
ticks = GetTickCount();
for (;;) { if (PeekMessage(&msg, NULL, WM_NULL, WM_KEYFIRST, PM_REMOVE)) { if (msg.message == WM_QUIT) { DestroyWindow(window); break; }
TranslateMessage(&msg); DispatchMessage(&msg); }//simulated work ticks2 = GetTickCount(); for (;;) { UINT i; volatile int dummy = 1; for (; i < 10000 && dummy; i++) ; if (GetTickCount() - ticks2 >= 10) break; }
printf("main loop %u tick latency\n", GetTickCount() - ticks); ticks = GetTickCount(); } }