Window: Bottom-up

User Guide

Intel® VTune™ Profiler User Guide

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ID 766319

Date 11/07/2023

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Window: Bottom-up

Use the Bottom-up window to analyze performance of each program from the bottom level when a child function is placed directly above its parent (bottom-up analysis).

To access this window: Click the Bottom-up tab. Depending on the analysis type, the Bottom-up window may include the following panes:

Bottom-up Pane

Data provided in the Bottom-up pane depends on the analysis, data collection type, and viewpoint you apply.

	Grouping menu. Each row in the grid corresponds to a grouping level (granularity) of program units (module, function, synchronization object, and others). For example, the data in the Hotspots viewpoint is grouped by Function/Call Stack.
	Call stack. Analyze a tree hierarchy of the call stacks that lead to the selected program unit. Click the triangle sign to expand a row and view call trees for each program unit. Each tree is a call stack that called the selected unit. Each tree lists all the program units that had only one caller in the same row, with an arrow indicating the call relationship. Program units that had more than one caller are split so that each caller has a separate row with the callers to that callee. If a function was called from different code lines (call sites) in the same parent function, the Bottom-up pane aggregates such stacks into one and sums up their CPU time. The full information on the stack is shown in the Call Stack pane. The time value for a row is equal to the sum of all the nested items from that row. NOTE: Call stack information is always available for the results of the User-Mode Sampling collection. It is also available for the results of the hardware event-based sampling collection, if you enabled the Collect stacks option during the analysis configuration. Otherwise, the Call Stack column for the event-based results shows "Unknown" entries in the call tree. If you see `[Unknown frame(s)]` identifiers for the functions, it means that the VTune Profiler could not locate symbol files for system or your application modules. See the Resolving Unknown Frame(s) topic for more details. If the VTune Profiler does not find debug information in binaries, it statically identifies function boundaries and assigns hotspot addresses to generated pseudo names `func@address` for such functions, for example:
	Performance metrics. Each data column in the grid corresponds to a performance metric. By default, all program units are sorted in the descending order by metric values in the fist column providing the most performance-critical program units first. You may click a column header to sort the table by the required metric. The list of performance metrics varies depending on the analysis type. Mouse over a column header (metric) to read the metric description, or right-click and select the What's This Column? option from the context menu. If a metric has a threshold value set up by the VTune Profiler architect and this value is exceeded, the VTune Profiler highlights such a value in pink. You may mouse over a pink cell to read the description of the detected issue and tuning advice for this issue. For some analysis types, you may see grayed out metric values in the grid, which indicates that the data collected for such a metric is unreliable. This may happen, for example, if the number of samples collected for PMU events is too low. In this case, when you hover over such an unreliable metric value, the VTune Profiler displays a message: The amount of collected PMU samples is too low to reliably calculate the metric. Depending on the analysis type and viewpoint, the Bottom-up view may represent the CPU Time by utilization levels. Focus your tuning efforts on the program units with the largest Poor value. This means that during the execution of these program units your application underutilized the CPU time. The overall goal of optimization is to achieve Ideal (green ) or OK (orange ) CPU utilization state and shorten the Poor and Over CPU utilization values.
	Toolbar. Select the following options to manage the Bottom-up view: Click the Customize Grouping button to open the Custom Grouping dialog box. Click the Find button to open a search bar and search for a string in the grid. Click the Change Stack Layout button to switch between call stack layouts. Chain layouts are typically more useful for the bottom-up view: While tree layouts are more natural for the top-down view:

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