here - Stefan-Marr.de

3. Which Concepts for Concurrent and Parallel Progr. does a VM need to Support?
in the VM to gather a wide range of runtime information for adaptive optimizations,
e. g., high-level communication behavior and low-level data access
frequency information. Further extensions, for instance to inspect and manipulate
the runtime stack or the heap layout, would be useful as well. Thus a
VM needs to provide advanced infrastructure for dynamic optimization as
well as facilities for customizable runtime feedback and monitoring.
Policies for execution and state access require support from the VM to be
enforced and need to be integrated with reflection. The second conclusion
is that concepts that require VM support to guarantee their semantics show
a number of commonalities. These concepts vary in only a small number
of aspects, but with these variations they achieve different sets of language
guarantees. The first aspect is the semantics of executing code or invoking
methods, and the second aspect is the accessibility and mutability of state. An
additional common problem is that these basic aspects need to be properly
integrated with concepts such as reflection to achieve the desired semantics.
Improving performance and improving the support for language semantics
are two distinct research projects. To improve execution performance,
an investigation of dynamic compilation, adaptive optimization, and runtime
monitoring techniques is necessary. The main focus is on finding efficient techniques
to gather and utilize a wide range of different runtime information to
adapt execution dynamically. Such research is expected to yield improvement
for non-functional system requirements.
In contrast, improved support for language semantics requires an investigation
of correctness issues and techniques for changing language behavior.
While performance is an issue here as well, the focus is on providing more
flexibility to language developers to adapt execution semantics as necessary.
Thus, this research is expected to yield improvements for functional requirements.
While performance is a relevant aspect for this research question as
well, it is not in the focus. To conclude, the two research questions are distinct.
Therefore, from our perspective, they should be tackled by two distinct
research projects in order to provide the projects with a clear scope and research
goal.
This dissertation concentrates on improving support for language semantics
in VMs as the first step in order to achieve a full understanding of the
corresponding problems and to treat the question comprehensively. The main
reason is to concentrate on improving functional concerns first and therefore
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