diff -Napur -X /home/jbarnes/dontdiff linux-2.6.20/arch/x86_64/kernel/entry.S linux-2.6.20-delay-hack/arch/x86_64/kernel/entry.S
--- linux-2.6.20/arch/x86_64/kernel/entry.S	2007-02-04 10:44:54.000000000 -0800
+++ linux-2.6.20-delay-hack/arch/x86_64/kernel/entry.S	2007-04-20 13:27:33.000000000 -0700
@@ -231,6 +231,8 @@ ENTRY(system_call)
 	GET_THREAD_INFO(%rcx)
 	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%rcx)
 	jnz tracesys
+	jmp syscall_delay_hack
+ret_from_delay:
 	cmpq $__NR_syscall_max,%rax
 	ja badsys
 	movq %r10,%rcx
@@ -302,6 +304,12 @@ badsys:
 	movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
 	jmp ret_from_sys_call
 
+syscall_delay_hack:	
+	SAVE_ALL
+	call syscall_delay
+	RESTORE_ALL
+	jmp ret_from_delay
+
 	/* Do syscall tracing */
 tracesys:			 
 	SAVE_REST
diff -Napur -X /home/jbarnes/dontdiff linux-2.6.20/arch/x86_64/kernel/irq.c linux-2.6.20-delay-hack/arch/x86_64/kernel/irq.c
--- linux-2.6.20/arch/x86_64/kernel/irq.c	2007-02-04 10:44:54.000000000 -0800
+++ linux-2.6.20-delay-hack/arch/x86_64/kernel/irq.c	2007-04-20 10:37:40.000000000 -0700
@@ -97,6 +97,16 @@ skip:
 	return 0;
 }
 
+static int irq_delay;
+
+static int __init irq_delay_hack(char *str)
+{
+	irq_delay = simple_strtol(str, NULL, 0);
+	return 1;
+}
+__setup("irq_delay=", irq_delay_hack);
+
+
 /*
  * do_IRQ handles all normal device IRQ's (the special
  * SMP cross-CPU interrupts have their own specific
@@ -110,6 +120,9 @@ asmlinkage unsigned int do_IRQ(struct pt
 	unsigned vector = ~regs->orig_rax;
 	unsigned irq;
 
+	/* IRQ delay hack to measure performance hit */
+	ndelay(irq_delay);
+
 	exit_idle();
 	irq_enter();
 	irq = __get_cpu_var(vector_irq)[vector];
diff -Napur -X /home/jbarnes/dontdiff linux-2.6.20/arch/x86_64/kernel/setup.c linux-2.6.20-delay-hack/arch/x86_64/kernel/setup.c
--- linux-2.6.20/arch/x86_64/kernel/setup.c	2007-02-04 10:44:54.000000000 -0800
+++ linux-2.6.20-delay-hack/arch/x86_64/kernel/setup.c	2007-04-20 11:10:35.000000000 -0700
@@ -1239,3 +1239,18 @@ static __init int add_pcspkr(void)
 }
 device_initcall(add_pcspkr);
 #endif
+
+static int syscall_delay_nsec;
+
+static int __init syscall_delay_hack(char *str)
+{
+	syscall_delay_nsec = simple_strtol(str, NULL, 0);
+	return 1;
+}
+__setup("syscall_delay=", syscall_delay_hack);
+
+void syscall_delay(void)
+{
+	ndelay(syscall_delay_nsec);
+}
+
diff -Napur -X /home/jbarnes/dontdiff linux-2.6.20/Makefile linux-2.6.20-delay-hack/Makefile
--- linux-2.6.20/Makefile	2007-02-04 10:44:54.000000000 -0800
+++ linux-2.6.20-delay-hack/Makefile	2007-04-20 11:07:28.000000000 -0700
@@ -1,7 +1,7 @@
 VERSION = 2
 PATCHLEVEL = 6
 SUBLEVEL = 20
-EXTRAVERSION =
+EXTRAVERSION = -delay-hack
 NAME = Homicidal Dwarf Hamster
 
 # *DOCUMENTATION*