Scalable Comparative Visualization of Ensembles of Call Graphs

Abstract

Optimizing the performance of large-scale parallel codes is critical for efficient utilization of computing resources. Code developers often explore various execution parameters, such as hardware configurations, system software choices, and application parameters, and are interested in detecting and understanding bottlenecks in different executions. They often collect hierarchical performance profiles represented as call graphs, which combine performance metrics with their execution contexts. The crucial task of exploring multiple call graphs together is tedious and challenging because of the many structural differences in the execution contexts and significant variability in the collected performance metrics (e.g., execution runtime). In this paper, we present an enhanced version of CallFlow to support the exploration of ensembles of call graphs using new types of visualizations, analysis, graph operations, and features. We introduce ensemble-Sankey, a new visual design that combines the strengths of resource-flow (Sankey) and box-plot visualization techniques. Whereas the resource-flow visualization can easily and intuitively describe the graphical nature of the call graph, the box plots overlaid on the nodes of Sankey convey the performance variability within the ensemble. Our interactive visual interface provides linked views to help explore ensembles of call graphs, e.g., by facilitating the analysis of structural differences, and identifying similar or distinct call graphs. We demonstrate the effectiveness and usefulness of our design through case studies on large-scale parallel codes.

TinyProf: Towards Continuous Performance Introspection through Scalable Parallel I/O

“…Analyzing individual process behavior and performance variability for various program entities is essential and required by performance visualization systems (e.g., Callflow [15]). In fact, the collected data includes massive local (within each process) and global (across processes) redundancies.…”

“…The profiles also provide detailed data for each process, allowing for an in-depth examination of processspecific behavior. TinyProf produces output files that can be easily converted to formats compatible with widely-used analysis and visualization tools, such as CallFlow [3], [15] and Hatchet [16], [17], through the use of a straightforward conversion script.…”

Designing an Interactive, Notebook-Embedded, Tree Visualization to Support Exploratory Performance Analysis

“…Xie et al [50] prioritizes locating anomalous CCTs in execution traces through an embedding approach. CallFlow [27,36] prioritizes showing the distribution of attributes and aggregates call sites by their module, using a Sankey diagram with embedded histograms and other distribution indicators as well as linked statistical charts to represent the resulting structure and encode performance metrics. Comparison across per-CPU trees was not a goal discussed in our interviews with target users, and thus we focus on tasks with preaggregated per-program trees.…”