Optimizing compilers perform various optimizations in order to exploit the best performance from computer systems. However, some kinds of optimizations cannot be applied if values of variables or system parameters are not known at compilation time. To solve this problem, we designed and implemented a system which collects such information at run time, and dynamically recompiles part of the program based on it. In our system, recompilation and management of runtime information are carried out on processors other than those which execute user programs. Therefore, recompilation cost does not affect the program execution time, unlike other similar systems. The evaluation result shows that quite high speedup can be attained with this method.