(GX) leave important note about MEM2

gx/mem2_manager.c

@@ -72,7 +72,15 @@ bool gx_init_mem2()
    u32 level;
    _CPU_ISR_Disable(level);
 
-   u32 size = SYS_GetArena2Size() - 1024 * 128; // leave some MEM2 for libogc
+   // BIG NOTE: MEM2 on the Wii is 64MB, but a portion of that is reserved for
+   // IOS. libogc by default defines the "safe" area for MEM2 to go from
+   // 0x90002000 to 0x933E0000. However, from my testing, I've found I need to
+   // reserve about 128KB for stuff like network and USB to work correctly.
+   // However, other sources says these functions need at least 0xE0000 bytes,
+   // 7/8 of a megabyte, of reserved memory to do this. My initial testing
+   // shows that we can work with only 128KB, but if some stuff mysteriously
+   // stops working, try fiddling with this size.
+   u32 size = SYS_GetArena2Size() - 1024 * 128;
 
    void *heap_ptr = (void *) ROUNDUP32(((u32) SYS_GetArena2Hi() - size));