Humphrey Burchell, Octave Larose, Stefan Marr

Profilers are crucial tools for identifying and improving ap-

plication performance. However, for language implementa-

tions with just-in-time (JIT) compilation, e.g., for Java and

JavaScript, instrumentation-based profilers can have signifi-

cant overheads and report unrealistic results caused by the

instrumentation.

In this paper, we examine state-of-the-art instrumentation-

based profilers for Java to determine the realism of their

results. We assess their overhead, the effect on compilation

time, and the generated bytecode. We found that the pro-

filer with the lowest overhead increased run time by 82×.

Additionally, we investigate the realism of results by test-

ing a profiler’s ability to detect whether inlining is enabled,

which is an important compiler optimization. Our results

document that instrumentation can alter program behavior

so that performance observations are unrealistic, i.e., they do

not reflect the performance of the uninstrumented program.

As a solution, we sketch late-compiler-phase-based in-

strumentation for just-in-time compilers, which gives us the

precision of instrumentation-based profiling with an over-

head that is multiple magnitudes lower than that of standard

instrumentation-based profilers, with a median overhead

of 23.3% (min. 1.4%, max. 464%). By inserting probes late in

the compilation process, we avoid interfering with compiler

optimizations, which yields more realistic results.

https://stefan-marr.de/downloads/mplr24-burchell-et-al-towards-realistic-results-for-instrumentation-based-profilers-for-jit-compiled-systems.pdf

https://doi.org/10.1145/3679007.3685058