Advanced Hotspots analysis is a fast and easy way to identify performance-critical code sections (hotspots). The periodic instruction pointer sampling performed by Intel® VTune™ Amplifier identifies code locations where an application spends more time than in others. A function may consume much time either because its code is slow or because the function is frequently called. But any improvements in the speed of such functions should have a bigger impact on overall application performance.
VTune Amplifier creates a list of functions in your application ordered by the amount of time spent in each function. By default, Advanced Hotspots analysis does not capture the function call stacks as the hotspots are collected, but it can be used to sample all processes on the system. This type of analysis uses event-based sampling collection and analyzes all the processes running on your system at the moment, providing CPU time data on whole system performance.
You still can analyze stacks for your application modules by selecting the collection level that includes stack analysis in the Advanced Hotspots pane. For example, selecting the Hotspots, call counts, stacks and context switches collection level extends the Advanced Hotspots analysis with performance, parallelism and power consumption data attributed to execution paths.
You can choose to view Advanced Hotspots analysis results in any of the following viewpoints:
Viewpoint | Description |
|---|---|
Hardware Event Counts | Displays the event count for all collected processor events. While the Hardware Event Sample Counts viewpoint provides the actual number of samples collected for an event, Hardware Event Count viewpoint estimates the number of times this event occurred during the collection. |
Hardware Event Sample Counts | Displays the sample count for all collected processor events. While the Hardware Event Counts viewpoint estimates the number of times an event occurred during the collection, the Hardware Event Sample Counts viewpoint provides the actual number of samples collected for this event. |
Hardware Issues | Helps identify where the application is not making the best use of available hardware resources. This viewpoint displays metrics derived from hardware performance counters. Hover over the highlighted metrics values in the grid to read why the extreme value might represent a performance problem. |
Hotspots | Helps identify hotspots - code regions in the application that consume a lot of CPU time. |
These viewpoints may include the following windows:
Summary window displays statistics on the overall application execution.
Bottom-up window displays performance data per metric (event ratio/event count/sample count) for each hotspot function.
PMU Events window displays count for PMU events selected for the analysis.
Uncore Events window displays counts of uncore events selected for the analysis. If there are no uncore events, the upper pane of the window is empty.
What's Next
You can go from the hotspots to the source code. View the source code containing the hotspots and modify your code to remove bottlenecks and improve the performance of your application.
Information provided by Advanced Hotspots analysis is important for tuning serial applications and it is still useful for tuning the serial sections of parallel applications. For algorithm tuning, you may also choose to run the Basic Hotspots analysis and analyze the call flow of the application or run the Concurrency analysis to estimate the effectiveness of the parallel algorithms you use. For Intel® Xeon Phi™ coprocessor analysis, you may run the General Exploration analysis type with additional metrics that help triage hardware issues in programs running on the coprocessor.