Breakpoint Performance (JVMTI)

[Christian Thalinger]

On Thu, 2009-04-09 at 05:40 +0000, Nicolas Michael wrote:
> process is becoming a lot more expensive. Sun Studio profiling shows that we
> spend almost 30% of the CPU time in handling breakpoints and related effort
> (e.g. running interpreted instead of JIT-compiled code for this class's
> methods).

I am taking care of CR 4836252, which should fix the interpreted method
problem.

> It seems, orig_bytecode_at(int) is iterating linearly over a list of all
> breakpoints of this class (in our case: about 1,000) to find the matching
> breakpoint:
> 
> Bytecodes::Code methodOopDesc::orig_bytecode_at(int bci) {
>   BreakpointInfo* bp = instanceKlass::cast(method_holder())->breakpoints();
>   for (; bp != NULL; bp = bp->next()) {
>     if (bp->match(this, bci)) {
>       return bp->orig_bytecode();
>     }
>   }
>   ShouldNotReachHere();
>   return Bytecodes::_shouldnotreachhere;
> }

The code is very simple and definitely could be optimized.  I'm just not
sure if it's worth.

-- Christian