We analyzed the UNIX 4.2 BSD file system by recording userlevel activity in trace files and writing programs to analyze the traces. The tracer did not record individual read and write operations, yet still provided tight bounds on what information was accessed and when. The trace analysis shows that the average file system bandwidth needed per user is low (a few hundred bytes per second). Most of the files accessed are open only a short time and are accessed sequentially. Most new information is deleted or overwritten within a few minutes of its creation. We also wrote a simulator that uses the traces to predict the performance of caches for disk blocks. The moderate-sized caches used in UNIX reduce disk traffic for file blocks by about 50%, but larger caches (several megabytes) can eliminate 90% or more of all disk traffic. With those large caches, large block sizes (16 kbytes or more) result in the fewest disk accesses. Trace-Driven Analysis of 4.2 BSD File System January 2, 1993 1...

This dissertation shows that operating systems can provide fundamental services an order of magnitude more efficiently than traditional implementations. It describes the implementation of a new operating system kernel, Synthesis, that achieves this level of performance. The Synthesis kernel combines several new techniques to provide high performance without sacrificing the expressive power or security of the system. The new ideas include: ffl Run-time code synthesis --- a systematic way of creating executable machine code at runtime to optimize frequently-used kernel routines --- queues, buffers, context switchers, interrupt handlers, and system call dispatchers --- for specific situations, greatly reducing their execution time. ffl Fine-grain scheduling --- a new process-scheduling technique based on the idea of feedback that performs frequent scheduling actions and policy adjustments (at submillisecond intervals) resulting in an adaptive, self-tuning system that can support real-ti...

v Abstract Caching has long been recognized as a powerful performance enhancement technique in many areas of computer design. Most modern computer systems include a hardware cache between the processor and main memory, and many operating systems include a software cache between the file system routines and the disk hardware. In a distributed file system, where the file systems of several client machines are separated from the server backing store by a communications network, it is desirable to have a cache of recently used file blocks at the client, to avoid some of the communications overhead. In this configuration, special care must be taken to maintain consistency between the client caches, as some disk blocks may be in use by more than one client. For this reason, most current distributed file systems do not provide a cache at the client machine. Those systems that do place restrictions on the types of file blocks that may be shared, or require extra communication to confirm that...

This paper reports on the effects of using hardware virtual memory assists in managing file buffer caches in UNIX. A controlled experimental environment was constructed from two systems whose only difference was that one of them (XMF) used the virtual memory hardware to assist file buffer cache search and retrieval. An extensive series of performance characterizations was used to study the effects of varying the buffer cache size (from 3 Megabytes to 70 MB); I/O transfer sizes (from 4 bytes to 64 KB); cache-resident and non-cacheresident data; reads and writes; and a range of application programs. The results: small read/write transfers from the cache (1KB) were 50% faster under XMF, while larger transfers (8KB) were 20% faster. Retrieving data from disk, the XMF improvement was 25% and 10% respectively, although open/close system calls took slightly longer in XMF. Some individual programs ran as much as 40% faster on XMF, while an application benchmark suite showed a 7--15% improvement in overall execution time. Perhaps surprisingly, XMF had fewer translation lookaside buffer misses.

This report describes the design and implementation of HASKELL system. The areas implemented are the lexical analysis, parsing, intepretation of the lambda tree, and machine code generation. Because of the size, complexity and novelty of the language many of these areas present particular difficulty. A considarable amount of meta-programming was used in order to tackle the size of the project. Contents Introduction v 1 Lexical Analysis 1 1.1 Technical Overview 1 1.2 General Description 3 1.3 The Layout Rule 4 1.4 Alternative Design 5 1.5 Coding for Speed 6 1.5.1 Token Recognition 7 1.5.2 Character Copying 8 1.5.3 Memory Allocation 9 1.5.4 Symbol Table Updates 9 1.5.5 The Ultimate Combination 9 1.5.6 Performance 10 1.6 Testing 10 2 Parsing 11 2.1 Technical Overview 11 2.2 General Description 12 2.3 Handling the Grammar Ambiguities 13 2.3.1 Definable Operators and Function Applications 13 2.3.2 General 15 2.3.3 September Version 15 2.3.4 April Grammar changes 17 2.3.5 April Version 18 ...