Prioritized Garbage Collection: Explicit GC Support for Software Caches

Programmers routinely trade space for time to increase performance, often in the form of caching or memoization. In managed languages like Java or JavaScript, however, this space-time tradeoff is complex. Using more space translates into higher garbage collection costs, especially at the limit of available memory. Existing runtime systems provide limited support for space-sensitive algorithms, forcing programmers into difficult and often brittle choices about provisioning. This paper presents prioritized garbage collection, a cooperative programming language and runtime solution to this problem. Prioritized GC provides an interface similar to soft references, called priority references, which identify objects that the collector can reclaim eagerly if necessary. The key difference is an API for defining the policy that governs when priority references are cleared and in what order. Application code specifies a priority value for each reference and a target memory bound. The collector reclaims references, lowest priority first, until the total memory footprint of the cache fits within the bound. We use this API to implement a space-aware least-recently-used (LRU) cache, called a Sache, that is a drop-in replacement for existing caches, such as Google's Guava library. The garbage collector automatically grows and shrinks the Sache in response to available memory and workload with minimal provisioning information from the programmer. Using a Sache, it is almost impossible for an application to experience a memory leak, memory pressure, or an out-of-memory crash caused by software caching.Comment: to appear in OOPSLA 201

Media representations of the nouveaux riches and the cultural constitution of the global middle class

The article offers a distinctive account of how the nouveaux riches serve as an anchor for a range of upper- middle- class ambivalences and anxieties associated with transformations of capitalism and shifting global hierarchies. Reflecting the long- term association of middle- class symbolic boundaries with notions of refinement and respectability, it examines how the discourse of civility shapes how the nouveaux riches are represented to the upper middle class, identifying a number of recurrent media frames and narrative tropes related to vulgarity, civility, and order. The author argues that these representations play a central role in the reproduction of the Western professional middle class, and in the cultural constitution of a global middle class — professional, affluent, urban, and affiliated by an aesthetic regime of civility that transcends national borders. The findings underline the significance of representations of the new super- rich as devices through which the media accomplish the global circulation of an upper- middle- class repertoire of cultural capital, which is used both to police shifting class boundaries and to establish a legitimate preserve for univorous snobbishness

The Somatic Genomic Landscape of Glioblastoma

We describe the landscape of somatic genomic alterations based on multi-dimensional and comprehensive characterization of more than 500 glioblastoma tumors (GBMs). We identify several novel mutated genes as well as complex rearrangements of signature receptors including EGFR and PDGFRA. TERT promoter mutations are shown to correlate with elevated mRNA expression, supporting a role in telomerase reactivation. Correlative analyses confirm that the survival advantage of the proneural subtype is conferred by the G-CIMP phenotype, and MGMT DNA methylation may be a predictive biomarker for treatment response only in classical subtype GBM. Integrative analysis of genomic and proteomic profiles challenges the notion of therapeutic inhibition of a pathway as an alternative to inhibition of the target itself. These data will facilitate the discovery of therapeutic and diagnostic target candidates, the validation of research and clinical observations and the generation of unanticipated hypotheses that can advance our molecular understanding of this lethal cancer

Incorporating domain-specific information into the compilation process

textDespite many advances in compiler research, traditional compilers continue to suffer from one significant limitation: they only recognize the low-level primitive constructs of their languages. In contrast, programmers increasingly benefit from higher level software components, which implement a variety of specialized domains—everything from basic file access to 3D graphics and parallel programming. The result is a marked difference between the level of abstraction in software development and the level of abstraction in compilation. In this thesis we present the Broadway compiler, which closes this gap. Broadway represents a new kind of compiler, called a library-level compiler, that supports domainspecific compilation by extending the benefits of compiler support to software libraries. The key to our approach is a separate annotation language that conveys domain-specific information about libraries to our compiler, allowing it to treat library routines more like built-in language operations. Using this information, the compiler can perform library-level program analysis and apply library-level optimizations. We explore both the opportunities and challenges presented by library-level compilation. We show that library-level optimizations can increase the performance of several parallel programs written using a highly-tuned parallel linear algebra library. These highlevel optimizations are beyond the capabilities of a traditional compiler and even rival the performance of programs hand-coded by an expert. We also show that our compiler is an effective tool for detecting a range of library-level errors, including several significant security vulnerabilities. Finally, we present a new client-driven pointer analysis algorithm, which provides precise and scalable program analysis to meet the demanding requirements of library-level compilation.Computer Science

Abstract An Annotation Language for Optimizing Software Libraries

This paper introduces an annotation language and a compiler that together can customize a library implementation for specific application needs. Our approach is distinguished by its ability to exploit high level, domain-specific information in the customization process. In particular, the annotations provide semantic information that enables our compiler to analyze and optimize library operations as if they were primitives of a domain-specific language. Thus, our approach yields many of the performance benefits of domain-specific languages, without the effort of developing a new compiler for each domain. This paper presents the annotation language, describes its role in optimization, and illustrates the benefits of the overall approach. Using a partially implemented compiler, we show how our system can significantly improve the performance of two applications written using the PLAPACK parallel linear algebra library.

Detecting errors with configurable whole-program dataflow analysis

In this paper, we present an automatic compiler-based approach for detecting programming errors. Our system uses a configurable and scalable whole-program dataflow analysis engine driven by highlevel programmer-written annotations. We show that our system can automatically detect a wide range of programmer errors in C programs, including improper use of libraries, information leaks, and security vulnerabilities. We show that the aggressive compiler analysis that our system performs yields precise results. Further, our system detects a wide range of errors with greater scalability than previous automatic approaches. For one important class of security vulnerabilities, our system automatically finds all known errors in five medium to large C programs without producing any false positives. 1