Using IDA Pro v6.8.150423 along with latest WinDBG (from SDK for 15063).  When launching IDA with a 64-bit file, and WinDBG as a debugger, things like breaking process, single stepping (step into / step over) take a long time (about ~3-5s).Using other debuggers along with IDA (i.e. Remote GDB or Local Bochs), this lag does not occur.  I have also tried removing plugins and fresh IDA install, etc...  Which does not help.Tracing the process (i.e. letting IDA run and log instructions) is fast, so the issue seems to be related to IDA loading something when single stepping (i.e. displaying stuff, re-loading things, etc) so I have tried to just keep the Debug View (IDA View-RIP) only open and other windows closed with no dice.
IDA Pro + WinDBG incredibly slow single stepping
ida;debugging;x86;windbg;x64