Abstract Worst-case resource usage provides a useful guidance in the design, configuration and deployment of software, especially when it runs under a context with limited amount of resources. Static resource-bound analysis can provide sound upper bounds of worst-case resource usage but may provide too conservative, even unbounded, results. In this paper, we present a resource-usage-aware fuzzing approach to estimate worst-case resource usage. The key idea is to guide the fuzzing process using resource-usage amount together with resource-usage relevant coverage. Moreover, we leverage semantic patch to make use of static analysis information (including control-flow, function-call, etc.) to instrument the original program, for the sake of aiding the subsequent fuzzing. We have conducted experiments to estimate worst-case resource usage of various resources in real-world programs, including heap memory, stack depths, sockets, user-defined resources, etc. The preliminary experimental results show the promising ability of our approach in estimating worst-case resource usage in real-world programs, compared with two state-of-the-art fuzzing tools (AFL and MemLock).

The classic linear (technically, affine) equality abstract domain, which can infer linear equality relations among variables of a program automatically, is one of the earliest and fundamental abstract domains. As a lightweight relational abstract domain, it has been widely used in program analysis. However, it cannot express non-convex properties that appear naturally due to the inherent disjunctive behaviors in a program. In this paper, we introduce a new abstract domain, namely the abstract domain of linear absolute value equalities, which generalizes the linear equality abstract domain with absolute value terms of variables. More clearly, we leverage the absolute value function to design the new abstract domain for discovering linear equality relations among values and absolute values of program variables. The new abstract domain can be used to infer piecewise linear behaviors (e.g., due to conditional branches, absolute value function calls, max/min function calls, etc.) in a program. Experimental results of our prototype are encouraging: In practice, the new abstract domain can find interesting piece-wise linear invariants that are non-convex and out of the expressiveness of the linear equality domain.

Integrating solid-state drives (SSDs) and shingled magnetic recording (SMR) drives can build cost-effective hybrid storage systems. However, both SSD and SMR drives endure inherent defects that are mutually exclusive. The write endurance of SSD is limited while SMR drives should prevent from writes due to the cleaning-caused performance degradation. In this paper, we propose Duchy, an endurable SSD caching scheme that simultaneously respects SMR constraints. Duchy filters ineffectual write traffic out of SSD without exacerbating the performance degradation of SMR drives. Meanwhile, Duchy leverages SSD to regulate the written zones in SMR drives to achieve controllable cleaning duration. Our experimental results indicate that compared with legacy SSD caching designs, only Duchy can achieve both system performance improvement and SSD write traffic reduction.

Modern Solid State Drives (SSDs) integrate more internal resources to get higher performance and capacity. Improving internal resource utilization by exploiting internal parallelism is important to enhance the performance of SSDs. Unfortunately, the internal resource utilization of SSDs is limited at runtime in practice because of the practical access conflicts to internal resources. In this paper, we propose a Conflict Eliminated Requests Based I/O Scheduler (CER-IOS) to better utilize internal parallelism of flash chips by scheduling I/O requests in a more fine-grained way. We introduce Conflict Eliminated Requests (CERs) in which parallelizable memory requests are grouped during the process of address translation in Flash Translation Layer. To schedule conflicting requests, we propose a small CER size prioritized resource distribution scheme, that ensures internal resources can always be distributed to valuable conflicting requests to further improve the efficiency of resource utilization. Our extensive experimental evaluation results show that CER-IOS provides significant improvement of resource utilization at runtime and reduces average I/O latency largely compared to state-of-the-art I/O schedulers implemented in operating systems.