ComDetective

Abstract

Inter-thread communication is a vital performance indicator in shared-memory systems. Prior works on identifying inter-thread communication employed hardware simulators or binary instrumentation and suffered from inaccuracy or high overheads-both space and time-making them impractical for production use. We propose ComDetective, which produces communication matrices that are accurate and introduces low runtime and low memory overheads, thus making it practical for production use. ComDetective employs hardware performance counters to sample memory-access events and uses hardware debug registers to sample communicating pairs of threads. ComDetective can differentiate communication as true or false sharing between threads. Its runtime and memory overheads are only 1.30× and 1.27×, respectively, for the 18 applications studied under 500K sampling period. Using ComDetective, we produce insightful communication matrices for microbenchmarks, PARSEC benchmark suite, and several CORAL applications and compare the generated matrices against MPI counterparts. Guided by ComDetective, we optimize a few codes and achieve up to 13% speedup. CCS CONCEPTS • General and reference → Performance; • Software and its engineering → Multithreading; • Computer systems organization → Multicore architectures.

Precise Event Sampling on AMD Versus Intel: Quantitative and Qualitative Comparison

“…To compare the precise event sampling capabilities of Intel and AMD for a full-fledged profiling tool, we use an open-source tool, ComDetective [3], which captures the interthread communication within an application. The main idea of ComDetective is to use PMU samples and debug register traps to detect cache line transfers between threads.…”

“…We performed experiments to compare the accuracy, overheads, and stability of ComDetective under PEBS and IBS running on the Intel Cascade Lake and the AMD Zen 2 machines. The sampling interval that we use in each experiment is 500K, which is the default sampling interval in the experiments reported in [3].…”

“…kernel mode or user mode. Lastly, to demonstrate how these microarchitectural characteristics impact tools that profile multithreaded applications, we study a full-fledged open-source tool, namely ComDetective [3], [34], that employs precise event sampling to detect interthread communication.…”

Precise event sampling‐based data locality tools for AMD multicore architectures

“…To detect inter-thread communications and measure data locality in multi-threaded code with low overheads, we substantially extend COMDETECTIVE, 14 a tool that captures inter-thread communications in the forms of communication matrices, and REUSETRACKER, 15 another tool that measures reuse distance in multi-threaded applications, to work in AMD machines. We introduced these tools in our previous works, 14,15 and developed them to interface with Intel PEBS in sampling memory accesses. In this work, we extend them to leverage Instruction Based Sampling (IBS) facility when running on AMD machines to sample memory loads and stores in detecting communications and measuring reuse distance.…”

“…In our experimental study, we firstly verify the accuracy of COMDETECTIVE + and REUSETRACKER + by using the microbenchmarks introduced in 14 and in 15 on an AMD multicore. We also perform sensitivity analysis to evaluate the impacts of different thread counts, sampling intervals, and debug register counts on the accuracy of our tools.…”