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Eric Brewer 2006-08-20 05:47:16 +00:00
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18
doc/paper3/LLADD.tex
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@ -649,7 +649,7 @@ practice. Most read-modify-write actions can be implemented as
user-defined operations, including common DBMS optimizations such as user-defined operations, including common DBMS optimizations such as
increment operations. The power of \yad is that by following these increment operations. The power of \yad is that by following these
local restrictions, we enable new operations that meet the global local restrictions, we enable new operations that meet the global
properties for correct, concurrent transactions.~\rcs{What was supposed to come after ``global''?} invariants for correct, concurrent transactions.
Finally, for some applications, the overhead of logging information for redo or Finally, for some applications, the overhead of logging information for redo or
undo may outweigh their benefits. Operations that wish to avoid undo undo may outweigh their benefits. Operations that wish to avoid undo
@ -729,7 +729,7 @@ needs to be forced to disk once.
The transactions described above only provide the The transactions described above only provide the
``Atomicity'' and ``Durability'' properties of ACID. ``Atomicity'' and ``Durability'' properties of ACID.
``Isolation'' is ``Isolation'' is
typically provided by locking, which is a higher-level but typically provided by locking, which is a higher level but
compatible layer. ``Consistency'' is less well defined but comes in compatible layer. ``Consistency'' is less well defined but comes in
part from low-level mutexes that avoid races, and in part from part from low-level mutexes that avoid races, and in part from
higher-level constructs such as unique key requirements. \yad, as with DBMSs, higher-level constructs such as unique key requirements. \yad, as with DBMSs,
@ -1033,7 +1033,7 @@ optimizations and a wide-range of transactional systems.
routines and recovery semantics. In this section, we show that this routines and recovery semantics. In this section, we show that this
flexibility does not come with a significant performance cost for flexibility does not come with a significant performance cost for
general purpose transactional primitives, and show how a number of general purpose transactional primitives, and show how a number of
special purpose interfaces aid in the development of higher level special purpose interfaces aid in the development of higher-level
code while significantly improving application performance. code while significantly improving application performance.
\subsection{Experimental setup} \subsection{Experimental setup}
@ -1075,7 +1075,7 @@ bug or misuse of the feature.
With the lock manager enabled, Berkeley With the lock manager enabled, Berkeley
DB's performance in the multithreaded test in Section~\ref{sec:lht} strictly decreased with DB's performance in the multithreaded test in Section~\ref{sec:lht} strictly decreased with
increased concurrency. (The other tests were single-threaded.) increased concurrency. (The other tests were single threaded.)
Although further tuning by Berkeley DB experts would probably improve Although further tuning by Berkeley DB experts would probably improve
Berkeley DB's numbers, we think that we have produced a reasonably Berkeley DB's numbers, we think that we have produced a reasonably
@ -1111,8 +1111,8 @@ This section presents two hashtable implementations built on top of
\yad, and compares them with the hashtable provided by Berkeley DB. \yad, and compares them with the hashtable provided by Berkeley DB.
One of the \yad implementations is simple and modular, while One of the \yad implementations is simple and modular, while
the other is monolithic and hand-tuned. Our experiments show that the other is monolithic and hand-tuned. Our experiments show that
\yads performance is competitive, both with single threaded, and \yads performance is competitive, both with single-threaded and
high-concurency transactions. high-concurrency transactions.
%Although the beginning of this paper describes the limitations of %Although the beginning of this paper describes the limitations of
%physical database models and relational storage systems in great %physical database models and relational storage systems in great
@ -1379,7 +1379,7 @@ the stream of requests that \yad is processing. For example, if
requests manipulate disjoint sets of data, they can be split across requests manipulate disjoint sets of data, they can be split across
many nodes, providing load balancing. If many requests perform many nodes, providing load balancing. If many requests perform
duplicate work, or repeatedly update the same piece of information, duplicate work, or repeatedly update the same piece of information,
they can be merged into a single request (RVM's ``log-merging'' they can be merged into a single request (RVM's ``log merging''
implements this type of optimization~\cite{lrvm}). Stream aggregation implements this type of optimization~\cite{lrvm}). Stream aggregation
techniques and relational albebra operators could be used to techniques and relational albebra operators could be used to
efficiently transform data while it is still laid out sequentially in efficiently transform data while it is still laid out sequentially in
@ -1675,7 +1675,7 @@ into a larger logical unit~\cite{experienceWithQuickSilver}.
As mentioned in Section~\ref{sec:system}, Berkeley DB is a system As mentioned in Section~\ref{sec:system}, Berkeley DB is a system
quite similar to \yad, and essentially provides raw access to quite similar to \yad, and essentially provides raw access to
transactional data structures for application transactional data structures for application
programmers~\cite{libtp}. As we mentioned earlier, we beleive that programmers~\cite{libtp}. As we mentioned earlier, we believe that
\yad is general enough to support a library like Berkeley DB, but that \yad is general enough to support a library like Berkeley DB, but that
Berkeley DB is too specialized to be useful to a reimplementation of Berkeley DB is too specialized to be useful to a reimplementation of
\yad. \yad.
@ -1690,7 +1690,7 @@ top of the chunks that these machines export.
systems intelligentally compose a set of systems for scalability and systems intelligentally compose a set of systems for scalability and
fault tolerance. In contrast, \yad makes it easy to push intelligence fault tolerance. In contrast, \yad makes it easy to push intelligence
into the individual nodes, allowing them to provide primitives that into the individual nodes, allowing them to provide primitives that
are appropriate for the higher level service. are appropriate for the higher-level service.
\subsection{Data layout policies} \subsection{Data layout policies}