VM '04 Abstract
Pp. 8396 of the Proceedings
Kernel Plugins: When a VM Is Too Much
Ivan Ganev, Greg Eisenhauer, and Karsten Schwan, Georgia Institute of Technology
This paper presents kernel plugins, a framework for dynamic
kernel specialization inspired by ideas borrowed from virtualization
research. Plugins can be created and updated inexpensively on-the-fly
and they can execute arbitrary user-supplied functions such that
neither safety nor performance are compromised. Three key techniques
are used to implement kernel plugins: (1) hardware fault isolation,
(2) dynamic code generation, and (3) dynamic linking. Hardware fault
isolation protects kernel-level services from plugin misbehavior,
dynamic code generation enables rapid online creation of arbitrary
plugins, and dynamic linking governs the kernel/plugin interface.
We discuss the design and implementation of the kernel plugin
facility, as well as its advantages and shortcomings. Its use is
demonstrated by a range of micro- and macro-benchmarks and a real-life
application featuring plugins that dynamically transcode images served
by a high-performance kernel web server. Benefits realized from
plugins can be both qualitative (adapting services to clients' needs),
and quantitative (improving performance through co-location of
application plugin code with kernel services). Plugins are implemented
in GNU/Linux on the Intel x86 platform. Reported performance results
include plugin upcalls in 0.45-0.62 , dynamic code generation
in 4 , and linking/unlinking in 3.1/1.6 for an image
grayscaling plugin - a dynamically code generated 66-line function
written in a subset of C. All results are measured on an 866 MHz
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