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@ -1510,25 +1510,36 @@ complexity by providing logical undos, and by leaving lock management
to higher-level code. This separates write-back and concurrency to higher-level code. This separates write-back and concurrency
control policies from data structure implementations. control policies from data structure implementations.
Camelot made a number of important Camelot made a number of important contributions, both in system
contributions, both in system design, and in algorithms for design, and in algorithms for distributed transactions~\cite{camelot}.
distributed transactions~\cite{camelot}. It leaves locking to application level code, It leaves locking to application level code, and updates data in
and updates data in place. (Argus uses shadow copies to provide place. (Argus uses shadow copies to provide atomic updates.) Camelot
atomic updates.) Camelot provides two logging modes: redo only provides two logging modes: physical redo-only (no-steal, no-force)
(no-steal, no-force) and undo/redo (steal, no-force). It uses and physical undo/redo (steal, no-force). Because Camelot does not
facilities of Mach to provide recoverable virtual memory. It support logical undo, concurrent operations must be implemented
supports Avalon, which uses Camelot to provide a similarly to those built with Argus. Camelot is similar to \yad in
higher-level (C++) programming model; Camelot provides a lower-level that its low-level C interface is designed to enable multiple
C interface that enables other programming models as well. It provides a limited form of closed nested transactions higher-level programming models, such as Avalon's C++ interface or an
where parents are suspended while children are active. Camelot also early version of RVM. However, like other distributed programming
provides mechanisms for distributed transactions and transactional models, Camelot focuses on a particular class of distributed
RPC. Although Camelot does allow applications to provide their own lock transactions. Therefore, it hard-codes assumptions regarding the
managers, implementation strategies for concurrent operations structure of nested transactions, consensus algorithms, communication
in Camelot are similar to those mechanisms, and so on.
built using Argus since Camelot does not provide logical undo. Camelot focuses
on distributed transactions, and hard-codes %It uses
assumptions regarding the structure of nested transactions, consensus %facilities of Mach to provide recoverable virtual memory. It
algorithms, communication mechanisms, and so on. %supports Avalon, which uses Camelot to provide a
%higher-level (C++) programming model; Camelot provides a lower-level
%C interface that enables other programming models as well. It provides a limited form of closed nested transactions
%where parents are suspended while children are active. Camelot also
%provides mechanisms for distributed transactions and transactional
%RPC. Although Camelot does allow applications to provide their own lock
%managers, implementation strategies for concurrent operations
%in Camelot are similar to those
%built using Argus since Camelot does not provide logical undo. Camelot focuses
%on distributed transactions, and hard-codes
%assumptions regarding the structure of nested transactions, consensus
%algorithms, communication mechanisms, and so on.
More recent transactional programming schemes allow for multiple More recent transactional programming schemes allow for multiple
transaction implementations to cooperate as part of the same transaction implementations to cooperate as part of the same
@ -1549,25 +1560,28 @@ concurrently with their children~\cite{omtt}.
QuickSilver is a distributed transactional operating system. It QuickSilver is a distributed transactional operating system. It
provides a transactional IPC mechanism, and provides a transactional IPC mechanism, and
allows varying degrees of isolation, both to support legacy code, and allows varying degrees of isolation, both to support legacy code, and
to implement servers that require special isolation properties. It to implement servers that require special isolation properties.
supports transactions over durable and volatile state, and includes a %It
number of different commit protocols. Its shared logging facility does not %supports transactions over durable and volatile state, and includes a
%number of different commit protocols.
Interestingly, its shared logging facility does not
hard-code log format or recovery algorithms, and supports a number hard-code log format or recovery algorithms, and supports a number
of interesting optimizations such as distributed of interesting optimizations such as distributed
logging~\cite{recoveryInQuickSilver}. The QuickSilver project found logging~\cite{recoveryInQuickSilver}. QuickSilver's logging mechanism
that transactions meet the demands of most is general enough to support \yad.
The QuickSilver project showed that transactions meet the demands of most
applications, provided that long-running transactions do not exhaust applications, provided that long-running transactions do not exhaust
system resources, and that flexible concurrency control policies are system resources, and that flexible concurrency control policies are
available. In QuickSilver, nested transactions would available. Nested transactions are
be most useful when a series of program invocations particularly useful when a series of program invocations
form a larger logical unit~\cite{experienceWithQuickSilver}. form a larger logical unit~\cite{experienceWithQuickSilver}.
Clouds is an object-oriented, distributed transactional operating Clouds is an object-oriented, distributed transactional operating
system. It uses shared abstract system. It uses shared abstract types~\cite{sharedAbstractTypes} and
types~\cite{sharedAbstractTypes} to provide concurrency control per-object atomicity specifications to provide concurrency control
among the objects in the system~\cite{clouds}. With the aid of among the objects in the system~\cite{clouds}. These formalisms could
per-method atomicity specifications, it provides higher concurrency be used during the design of high-concurrency \yad operations.
than QuickSilver, but is not designed for legacy applications.
\subsection{Data Structure Frameworks} \subsection{Data Structure Frameworks}