Transcript Effects of the Single Address Space Paradigm on CPU and OS

Effects of the Single Address Space Paradigm
on CPU and OS Design for a
Distributed Computer System
Donald S. Miller
ASU 64-bit OS Group
4/7/2016
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What’s a Paradigm?
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Constellation of beliefs, values, techniques and so on shared by the
members of a given community that implicitly define the legitimate
problems and methods of a research field for succeeding generations
of practitioners1
 attracts an enduring group of adherents away from competing
modes of scientific activity
 sufficiently open-ended to leave all sorts of problems for the
group of practitioners to resolve
Includes law theory, application and instrumentation together
Examples:
Aristotle’s physics, Ptolemaic astronomy, Galileo’s motion studies,
Copernican astronomy, Newtonian mechanics, Einstein's relativity
and
Process-Oriented OSs and Single Address Space Operating Systems
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1. The Structure of Scientific Revolutions, 3rd Edition, Thomas S. Kuhn, University of Chicago Press, 1996.
ASU 64-bit OS Group
4/7/2016
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Process-Oriented Paradigm
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ASU 64-bit OS Group
Each process runs in it’s own virtual address space
 virtual addresses are (process) context dependent
Process boundaries encapsulate and bind temporary virtual
address spaces, execution state, objects, protection domains and
principals
Persistent storage is in a separate namespace - the file system
Message-based communication or RPC on top of message passing
is the most prevalent mechanism for data exchange and
synchronization between executing entities
Page-based object granularity
Threads encapsulated within a process - domain crossing and
machine migration without an address space and thread context
switch essentially impossible
Layered system structure - operating system kernel and services
and user-level servers and programs layered on top of each other
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Process-Oriented Paradigm (continued)
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ASU 64-bit OS Group
Obtaining operating system services requires a domain crossing
AND entry into privileged supervisor mode
Process and data migration difficult - involves creating a new
namespace for data (DSM) and dealing with distinct machine
namespaces for code
Difficult to directly support OOD and OOP - preprocessors and
OS run-time systems are needed
OS support for protection implementation protection policy are
intertwined
Access authorization, resource accounting and name services
typically require kernel services or intervention
Copy set management is usually page-based and requires
broadcasts reducing scalability
Network-wide fault tolerance requires additional mechanisms
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Process-Oriented Paradigm (concluded)
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ASU 64-bit OS Group
Examples of Process-Oriented operating systems
 Industrial
 MULTICS, UNIX, MVS, Mach, Chorus, VMS, NT
 Research
 Exokernel, L4, SPIN
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Single Address Space Paradigm
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All programs run in a single virtual address space that covers all
levels of the memory hierarchy, all nodes of a network and
persists for the life of the computer system. This leads to the
following 5 properties.
1. Permanent and unique binding of all data and code to virtual addresses.
2. The ability to freely reassociate memory objects, access rights, protection
domains, virtual addresses, principals and threads.
3. A single network-wide namespace backed by the local demand paged
memory management on every node and that includes all levels of the
memory cache hierarchy.
4. Object, thread and protection domain mobility across the entire networkwide virtual address namespace.
5. Separation of ownership of code and ownership of execution of a
computation.
ASU 64-bit OS Group
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Single Address Space Paradigm (continued)
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ASU 64-bit OS Group
All programs run in the same virtual address space
 virtual addresses are not context dependent
Execution state, objects, protection domains and principals are not
bound to virtual addresses and hence not bound to each other
Persistent storage is in the same virtual address namespace
Shared memory is the most prevalent mechanism for data
exchange and synchronization
Object granularity can be independent of page granularity
Threads can travel throughout the virtual address space without
an address space switch or a thread context switch
System architecture can be flat and modular - operating system
services, environment servers and user-level programs can be
made accessible to each other and themselves via simple
procedure calls and returns
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Single Address Space Paradigm (continued)
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Obtaining operating system services is orthogonal to entry into
privileged supervisor mode
Process and Data Migration is straight-forward - objects and
threads exist at the same virtual addresses on all nodes; kernel
structures can be replicated or represented by surrogates on
different nodes
OOD and OOP can be directly supported - a protection domain
can translate directly into an instantiation of an object class
available at the user level - preprocessors and OS run-time
systems are not needed; base classes can be extended via
overrides at the user level
Clean separation of OS support for protection implementation
and user-level definition of protection policy is simple
Access authorization, resource accounting and name services can
be done at the user level
The common virtual address space provides simple scaleable per
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object copy set management
and a lowest level cache for fault
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Single Address Space Paradigm (concluded)
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ASU 64-bit OS Group
Examples of Single Address Space Operating Systems
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Without additional protection hardware assistance
 Opal, Mungi, Arius, Carthage (KFRPC)
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With additional protection hardware assistance
 AS/400, MONADS, ToM, Carthage (FRPC), Sombrero
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Sombrero Principals
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SYSTEM ARCHITECTURE
Process Oriented OS
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ASU 64-bit OS Group
Layered system structure operating system kernel and
services and user-level servers
and programs layered on top of
each other
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Single Address Space OS
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System architecture can be flat
and modular - operating system
services, environment servers
and user-level programs can be
made accessible to each other
and themselves via simple
procedure calls and returns
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SYSTEM ARCHITECTURE
Process Oriented OS
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ASU 64-bit OS Group
Obtaining operating system
services requires a domain
crossing AND entry into
privileged supervisor mode
Single Address Space OS
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4/7/2016
Obtaining operating system
services is orthogonal to entry
into privileged supervisor mode
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ASU 64-bit OS Group
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SYSTEM ARCHITECTURE
Process Oriented OS
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ASU 64-bit OS Group
Difficult to directly support OOD
and OOP - preprocessors and OS
run-time systems are needed
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Single Address Space OS
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OOD and OOP can be directly
supported - a protection domain
can translate directly into an
instantiation of an object class
available at the user level preprocessors and OS run-time
systems are not needed; base
classes can be extended via
overrides at the user level
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SYSTEM ARCHITECTURE
Process Oriented OS
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ASU 64-bit OS Group
OS support for protection
implementation protection policy
are intertwined
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Single Address Space OS
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Clean separation of OS support for
protection implementation and userlevel definition of protection policy is
simple
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SYSTEM ARCHITECTURE
Process Oriented OS
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ASU 64-bit OS Group
Access authorization, resource
accounting and name services
typically require kernel services
or intervention
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Single Address Space OS
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Access authorization, resource
accounting and name services
can be done at the user level
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