Dynamic Analysis and Profiling of Multithreaded Systems - Advanced Operating Systems and Kernel Applications - page 180

Figure 9. Screenshot of the OVATION visualization tool

security, resource management, and so forth.
Measuring behavior in the layers that supports
application execution is crucial to gaining a com-
plete understanding of the broader system because
applications share resources (e.g., memory, files
and devices) via these layers. Complex interac-
tions and dependencies are often hidden and not
obviously understood by the systems engineer. As
large-scale systems are integrated together, these
hidden dependencies result in resource conflicts
and “causal chains” that lead to unexpected, and
often undesirable, behavior. The tools described in
this section allow profiling of execution that passes
through the operating system and middleware lay-
ers. One challenge faced by these tools and their
users is mapping these behaviors to higher-level
application and distributed events.

Runtime Language (CLR), is becoming increas-
ingly common in enterprise applications where
portability and security are key requirements.
Figure 10 illustrates a typical VM-based applica-
tion architecture where each user application is
independently layered above the VM.
The use of VMs to run “managed programs”
lends itself to more portable profiling. For example,
dynamic instrumentation of complete binaries for
VM platforms is more straightforward because
the bytecode represents a hardware agnostic, and
more abstract representation, of the binary code
(Gosling, 1995).
In general, profiling strategies for VMs, such
as sampling and instrumentation, are comparable
to their native counterparts; the main factors that
determine effectiveness of a given approach in-
clude (1) implementation complexity, (2) incurred
time/space overhead, and (3) level of detail in the
output. This section describes different methods
used for VM profiling and evaluates the advan-
tages and disadvantages of each.

Virtual machine profiling
techniqueS

The use of virtual machine, such as the Java
Virtual Machine and the Microsoft Common