developed at the IBM Almaden Research Center, which uses atomic tran.sactions as a unified failure recovery mechanism for a client-server structured distributed system. Transactions allow failure atomicity for related activities at a single server or at a number of independent servers. Rather than bundling transaction management into a dedicated language or recoverable object manager, Quicksilver exposes the basic commit protocol and log recovery primi-tives, allowing clients and servers to tailor their recovery techniques to their specific needs. Servers can implement their own log recovery protocols rather than being required to use a system-defined protocol. These decisions allow servers to make their own choices to balance simplicity, efficiency, and recoverability. Categories and Subject Descriptors: D.4.3 [Operating Systems]: File System Management-distrib-uted file systems; file organization; maintenance; D.4.5 [Operating Systems]: Reliability-FauZt-tolerance; checkpoint/restart; H.2.4 [Database Management]: Systems--distributed systems; trun.s-action processing

Efficient synchronization is important for achieving good performance in parallel programs, especially on large-scale multiprocessors. Most synchronization algorithms have been designed to run on a dedicated machine, with one application process per processor, and can suffer serious performance degradation in the presence of multiprogramming. Problems arise when running processes block or, worse, busy-wait for action on the part of a process that the scheduler has chosen not to run. In this paper we describe and evaluate a set of scheduler-conscious synchronization algorithms that perform well in the presence of multiprogramming while maintaining good performance on dedicated machines. We consider both large and small machines, with a particular focus on scalability, and examine mutual-exclusion locks, reader-writer locks, and barriers. The algorithms we study fall into two classes: those that heuristically determine appropriate behavior and those that use scheduler information to guid...