Peer-to-peer (P2P) cycle sharing over the Internet has become increasingly popular as a way to share idle cycles. A fundamental problem faced by P2P cycle sharing systems is how to incrementally monitor and verify, with low overhead, the execution of jobs submitted to a remote untrusted hosting machine, or cluster of machines. In this paper, we present the design and implementation of GripCop DSM, a novel incremental execution monitoring and verification scheme for software distributed shared memory (SDSM) programs running on remote clusters. Our scheme maximally leverages the shared memory abstraction provided by the SDSM system by extending the shared memory abstraction to the monitoring process by replicating one of the processes running on the host cluster to verify intermediate results at runtime. Our GripCop DSM employs two monitoring schemes: (i) a full-scale monitoring scheme that completely replicates the computation of a process running on the cluster; and (ii) a decoy monitoring scheme that deceives the host cluster into believing that full-scale monitoring is being performed without it ever actually being done, thereby incurring negligible overhead. Experiments show that the combined use of full-scale and decoy monitoring ensures faithful execution with low performance impact, even over a wide area network

A number of hardware and software techniques have been proposed to detect dynamic program behaviors that may indicate a bug in a program. Because these techniques suffer from high overheads they are useful in finding bugs in programs before they are released, but are significantly less useful in finding bugs in long-running programs on production systems -- the same bugs that are the most difficult to find using traditional techniques. In this paper we propose the Artemis1 is the Greek goddess of the hunt and wild animals. Our framework guides the hunt for wild bugs. compiler-based instrumentation framework that complements many pre-existing runtime monitoring techniques. The Artemis framework guides baseline monitoring techniques toward regions of the program where bugs are likely to occur, yielding a low asymptotic monitoring overhead. Artemis also facilitates system-load aware runtime monitoring that allows the monitoring coverage to be dynamically scaled up to take advantage of extra cycles when the system load is low, and dynamically scaled down to monitor only the most suspicious regions when the system load is high. Our experiments show that Artemis' asymptotic overhead can outperform the performance floor overhead of random sampling for many tools, and that Artemis can effectively guide a monitoring tool to the buggy regions of a program. Our experimental results show that Artemis applied to a hardware-based PC-invariance monitoring scheme and a value-based invariance detection and checking scheme significantly improves their runtime monitoring overhead (by up to 4.6 times) with moderate impact on their bug-detecting capabilities.

Manual debugging is tedious, as well as costly. The high cost has motivated the development of fault localization techniques, which help developers search for fault locations. In this paper, we propose a new statistical method, called SOBER, which automatically localizes software faults without any prior knowledge of the program semantics. Unlike existing statistical approaches that select predicates correlated with program failures, SOBER models the predicate evaluation in both correct and incorrect executions and regards a predicate as fault-relevant if its evaluation pattern in incorrect executions significantly diverges from that in correct ones. Featuring a rationale similar to that of hypothesis testing, SOBER quantifies the fault relevance of each predicate in a principled way. We systematically evaluate SOBER under the same setting as previous studies. The result clearly demonstrates the effectiveness: SOBER could help developers locate 68 out of the 130 faults in the Siemens suite by examining no more than 10 percent of the code, whereas the cause transition approach proposed by Holger et al. [2005] and the statistical approach by Liblit et al. [2005] locate 34 and 52 faults, respectively. Moreover, the effectiveness of SOBER is also evaluated in an "imperfect world", where the test suite is either inadequate or only partially labeled. The experiments indicate that SOBER could achieve competitive quality under these harsh circumstances. Two case studies with grep 2.2 and bc 1.06 are reported, which shed light on the applicability of SOBER on reasonably large programs

Automated localization of software bugs is one of the essential issues in debugging aids. Previous studies indicated that the evaluation history of program predicates may disclose important clues about underlying bugs. In this paper, we propose a new statistical model-based approach, called SOBER, which localizes software bugs without any prior knowledge of program semantics. Unlike existing statistical debugging approaches that select predicates correlated with program failures, SOBER models evaluation patterns of predicates in both correct and incorrect runs respectively and regards a predicate as bug-relevant if its evaluation pattern in incorrect runs differs significantly from that in correct ones. SOBER features a principled quantification of the pattern difference that measures the bug-relevance of program predicates.We systematically evaluated our approach under the same setting as previous studies. The result demonstrated the power of our approach in bug localization: SOBER can help programmers locate 68 out of 130 bugs in the Siemens suite when programmers are expected to examine no more than 10% of the code, whereas the best previously reported is 52 out of 130. Moreover, with the assistance of SOBER, we found two bugs in bc 1.06 (an arbitrary precision calculator on UNIX/Linux), one of which has never been reported before.

This paper makes two contributions to architectural support for software debugging. First, it proposes a novel statistics-based, on-the-fly bug detection method called PC-based invariant detection. The idea is based on the observation that, in most programs, a given memory location is typically accessed by only a few instructions. Therefore, by capturing the invariant of the set of PCs that normally access a given variable, we can detect accesses by outlier instructions, which are often caused by memory corruption, buffer overflow, stack smashing or other memory-related bugs. Since this method is statistics-based, it can detect bugs that do not violate any programming rules and that, therefore, are likely to be missed by many existing tools. The second contribution is a novel architectural extension called the Check Look-aside Buffer (CLB). The CLB uses a Bloom filter to reduce monitoring overheads in the recently-proposed iWatcher architectural framework for software debugging. The CLB significantly reduces the overhead of PC-based invariant debugging. We demonstrate a PC-based invariant detection tool called AccMon that leverages architectural, run-time system and compiler support. Our experimental results with seven buggy applications and a total of ten bugs, show that AccMon can detect all ten bugs with few false alarms (0 for five applications and 2-8 for two applications) and with low overhead (0.24-2.88 times). Several existing tools evaluated, including Purify, CCured and value-based invariant detection tools, fail to detect some of the bugs. In addition, Purify's overhead is one order of magnitude higher than AccMon's. Finally, we show that the CLB is very effective at reducing overhead.