Add instruction counter.

[qemu.git] / qemu-doc.texi

diff --git a/qemu-doc.texi b/qemu-doc.texi
index e8641178dbfa3b91f3461b94e818e2b16bedb2fd..057b9f655153a54d350fa7e5a60a048913e70e16 100644 (file)
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -965,6 +965,17 @@ On M68K this implements the "ColdFire GDB" interface used by libgloss.
 
 Note that this allows guest direct access to the host filesystem,
 so should only be used with trusted guest OS.
+
+@item -icount [N|auto]
+Enable virtual instruction counter.  The virtual cpu will execute one
+instruction every 2^N ns of virtual time.  If @code{auto} is specified
+then the virtual cpu speed will be automatically adjusted to keep virtual
+time within a few seconds of real time.
+
+Note that while this option can give deterministic behavior, it does not
+provide cycle accurate emulation.  Modern CPUs contain superscalar out of
+order cores with complex cache heirachies.  The number of instructions
+executed often has little or no correlation with actual performance.
 @end table
 
 @c man end