MethodHandles::lookup is optimized (@ForceInline) and so it may not
represent apple-to-apple comparison.StackWalker::getCallerClass
does have overhead compared to Reflection::getCallerClass and
need to get the microbenchmark in the jdk repo and rerun the numbers [1].
I'm not getting how getCallerClass is used and related to access check.
Can you elaborate?
Mandy
[1] https://bugs.openjdk.java.net/browse/JDK-8221623
On 7/2/19 6:07 AM, Kasper Nielsen wrote:
Hi Remi,
Yes, setting up a StackWalker is more or less free. It is just
wrapping a set of options.
public class StackWalkerPerf {
static final StackWalker sw =
StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
@Benchmark
public StackWalker stackWalkerSetup() {
return StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
}
@Benchmark
public Class<?> stackWalkerCallerClass() {
return sw.getCallerClass();
}
@Benchmark
public Lookup reflectionCallerClass() {
return MethodHandles.lookup();
}
}
Benchmark Mode Cnt Score Error Units
StackWalkerPerf.stackWalkerSetup avgt 10 11.958 ± 0.353 ns/op
StackWalkerPerf.reflectionCallerClass avgt 10 8.511 ± 0.415 ns/op
StackWalkerPerf.stackWalkerCallerClass avgt 10 1269.825 ± 66.471 ns/op
I'm using MethodHandles.lookup() in this test because it is cheapest
way to invoke Reflection.getCallerClass() without any tricks.
So real performance is likely better.
/Kasper
On Tue, 2 Jul 2019 at 13:53, Remi Forax <fo...@univ-mlv.fr> wrote:
Hi Kasper,
did you store the StackWalker instance in a static final field ?
Rémi
----- Mail original -----
De: "Kasper Nielsen" <kaspe...@gmail.com>
À: "core-libs-dev" <core-libs-dev@openjdk.java.net>
Envoyé: Mardi 2 Juillet 2019 11:09:11
Objet: Slow performance of StackWalker.getCallerClass() vs
Reflection.getCallerClass()
Hi,
Are there any security reasons for why StackWalker.getCallerClass()
cannot be made as performant as Reflection.getCallerClass()?
StackWalker.getCallerClass() is at least 100 times slower then
Reflection.getCallerClass() (~1000 ns/op vs ~10 ns/op).
I'm trying to retrofit some existing APIs where I cannot take a Lookup
object to do some access control checks.
But the performance of StackWalker.getCallerClass() is making it impossible.
Best
Kasper
