Running time vary on Microblaze after code modification

When I do开发者_JAVA百科 some modifications in my code that runs on Microblaze, I sometimes see a large discrepancy in runtime for the execution of code that follows the same path. To illustrate, what I really mean by same path, take this example,

if ( condition )
 execute_this();
else
 execute_that(); // Modified this function

So say if I modified the code for function execute_that, I would see change in runtime even when condition was set and function execute_this has not been modified. What can cause this? Memory Alignment of Functions? Cache? Any clue?

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Does the timing only change when you change the other function, or is it variable anyway?

Are you running an OS? Could other tasks pre-empt yours?

Are interrupts running? An interrupt during your function will change the runtime.

And, yes, cache effects could cause this.