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WindowsPerf Release 2.5.1

Everton Constantino

Everton Constantino

Thursday, August 31, 20237 min read

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Introduction

WindowsPerf is a (Linux perf inspired) lightweight Windows on Arm performance profiling tool. Profiling is based on ARM64 PMU (Performance Monitor Unit) and its hardware counters. Currently, WindowsPerf is in the early stages of development, but it already supports the counting model for obtaining aggregate counts of occurrences of special events, and sampling model for determining the frequencies of event occurrences produced by program locations at the function, basic block, and/or instruction levels.

Release 2.5.1

We are happy to announce the latest WindowsPerf release version 2.5.1. This major release is a continuation of WindowsPerf development. It combines updates from release 2.5.0 and adds new features that were missed previously.

This release introduces improvements to wperf-driver stability, experimental sampling --annotate command (see !231 for more details) and various bug-fixes. In this release we’ve also focused on a new sub-project wperf-lib which is a C API library wrapper for wperf user-space application.  Users now can develop their own C/C++ programs taking full advantage of counting and sampling features. wperf-lib for now on will be a part of WindowsPerf binary release.

We are also introducing basic export to perf.data. Right now it only outputs simple COMM and SAMPLE events. It will be extended in future releases and will include support for: counting, sampling, recording, annotate, reporting. And more! Note: this can be limited by what host OS supports.

Highlights from the 2.5.1 Release

You can find a full list of improvements here. Below is a summary of the release highlights

  • Add support for JSON output with --annotate, see !310,
  • Improve timeline feature, see !308,
  • Provide up to date wperf-lib support for WindowsPerf features and
  • Add experimental support for perf.data output format.
  • Specify raw events with -e, e.g. -e r1b (raw event 0x001b). See !184.
  • Specify event names in caps. See !186.
  • Specify raw events in event groups. See !187.
  • New wperf-lib project was added, See WPerf lib service.
  • New events and metrics for CPUs specified by the TS team. See Pull in data from Telemetry Solution.
  • New --timeout command line option replaces deprecated -d. See !277.
  • Support for --timeout in sampling. See !278.
  • Command wperf list now supports extended view with -v (verbose) option.
  • Users can now control wperf-driver counting timer periods (between 10ms and 100ms) with the new command line option --config (e.g. --config count.period=30). See !301.

Annotate example while sampling CPython

First make sure you have CPython compiled along with its PDB files. You can see detailed instructions here CPython cross-build on x64 machine targeting ARM64. Now start the python_d.exe executable and make sure it is pinned to a single core, here we assume it is on core 1. You can pin the application through the task manager or using the command:

> cmd /c “start /affinity 2 python_d.exe”

notice that the argument to affinity is an affinity mask not the core number itself. This will open up a window with a python console. Type the following command

>> 10**10**1000

Now go back to the command line and start wperf with:

> wperf sample -e ld_spec:100000 --pe_file python_d.exe  --pdb_file python_d.pdb --image_name python_d.exe -c 1  --annotate

Here follows part of the output you should see:

x_mul:python313_d.dll
        Source file                                               Line number  Hits
        ===========                                               ===========  ====
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3559         98
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3560         48
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3562         22
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3558         17
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3561         15
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3563         6
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3542         2
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3540         1
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3557         1
        C:\Users\$USER\source\repos\cpython\Objects\longobject.c  3571         1


The first information is the function symbol, here is the x_mul function of the python313_d.dll so all information down below pertains to that function, you will see sections like this for all functions that have at least a single sample. The details that follow come from the python313_d.pdb PDB file, the first column represents the file the function is defined. The second column contains the line number within the file and the third column the number of samples for that particular line number. Notice that the driver generates just a set of program counters when a particular event overflows the PMU counters so we have to map that memory address to a particular line number inside the source code that might actually contain a range of memory locations.

Sampling output is available also as JSON. Please use --json command line flag. Please note that in the future JSON format will have richer content depending on the -v (verbose) flag used with --json.

Changes to command line options

We are in the process of aligning command line options. We’ve moved with !305 towards normalised command line options. We want all command line options with one hyphen (like -option) to be replaced with --option. Single letter command line options like -v will not change. With the upcoming release 3.0 we will migrate to this model. From release 2.5.1 onward we support both -option and --option to give users time to transition to the new command line style.

WindowsPerf releases update

We’re planning to have a major release every three months with the next release 3.0.0 coming in September/October 2023. During the time between the releases, we will be able to implement 2-3 new major features (derived from our requirements), improve documentation and fix issues. 

You can read more about previous releases here.

Where to find us?

For source code and binary releases please visit our WindowsPerf webpage at GitLab. Additional project resources include WindowsPerf Wiki and WindowsPerf JIRA project board.

If you have any questions, issues you would like to raise please visit our WindowsPerf GitLab issue page and create a new issue with a clear description of the problem you’re facing or issue you want help with.