Over the last few years I’ve written over forty blog posts that discuss ETW/xperf profiling. I’ve done this because it’s one of the best profilers I’ve ever used, and it’s been woefully undersold and under documented by Microsoft. My goal has been to let people know about this tool, make it easier for developers and users to record ETW traces, and to make it as easy as possible for developers to analyze ETW traces.
Some of those posts have aged poorly, and the rest are hidden amongst the 210+ posts (really? wow) I’ve written. The purpose of this page is to be a central hub that links to the ETW/xperf posts that are still relevant. Also, I’ve updated many of the older posts to reflect changes in the ETW toolset (technically known as the Windows Performance Toolkit). For convenience this page is accessible as https://tinyurl.com/etwcentral.
The most important post describes how to record ETW traces. This is important because ETW traces can be recorded on one machine, and analyzed on another. This means that your customers or relatives can record ETW traces and then you can analyze them. Remote diagnosis of issues is a wonderful superpower. The article describing how to record an xperf/ETW trace can be found here – share it with those who have performance problems:
Once you’ve got a trace you need to analyze it (or share it with someone who can). The most comprehensive resource I’ve created for learning how to analyze ETW traces is the series of three videos I created in 2014. More information and links to the videos can be found here:
For more details, or if you don’t want to watch videos, there are many tutorial blog posts available, listed here in rough order of importance:
- UIforETW – Windows Performance Made Easier
- WPA–Xperf Trace Analysis Reimagined – basics of WPA trace analysis
- Xperf for Excess CPU Consumption: WPA edition – basics of investigating CPU consumption
- Xperf Wait Analysis–Finding Idle Time – wait analysis (idle CPU investigations) with UIforETW and WPA 10
- New Xperf and new WPA in the new WPT – new features in WPT 10
- Graph All the Things (Using WPT 10) – graphing custom ETW data
- New Version of Xperf–Upgrade Now – new features in WPT 8.1
- ETW Heap Tracing–Every Allocation Recorded – tracing memory allocations
- ETW Heap Snapshots – tracing all outstanding allocations (much less data than ETW Heap Tracing)
- ETW Flame Graphs Made Easy – using WPA’s flame graphs to visualize CPU usage, and more
- Exporting Arbitrary Data from xperf ETL files
- CPU Performance Counters on Windows – recording per-process CPU performance counters using ETW
- Process Tree from an Xperf Trace – an example of exporting ETL data
- ETW Trace Compression (and xperf syntax refresher) – low-level details on how recording traces works, handy if you want to modify UIforETW
- Bulk ETW Trace Analysis in C#
Doing precise analysis of an ETW trace requires knowing exactly what the many columns in the tables mean. Some of those table columns are documented in these blog posts, updated in 2016 for the latest version of WPA:
- The Lost Xperf Documentation–CPU sampling
- The Lost Xperf Documentation—CPU Scheduling
- The Lost Xperf Documentation—Disk Usage
ETW investigation write-ups:
Some of my favorite blog posts are those that tell a tale of noticing some software that I use being slow, recording a trace, and figuring out the problem. In most cases this let me come up with a workaround, and in many cases the (ridiculously!) detailed bug reports or the attention the posts drew led to the problems being fixed.
Many of the articles linked to below have not yet been updated. It’s an ongoing process but I think it’s worth publishing this now without waiting for all of the updates to finish.
I’ve categorized the investigations by what product was investigated. And, as a reminder, with the exception of the fractal software investigation all of these are looking at problems in software that I don’t work on.
Visual Studio and VC++ code-gen:
- Xperf and Visual Studio: The Case of the Breakpoint Hangs
- Visual C++ Debug Builds–”Fast Checks” Cause 5x Slowdowns
- Visual Studio Single Step Performance Fixes
- Make VC++ Compiles Fast Through Parallel Compilation
- You Got Your Web Browser in my Compiler!
- Self Inflicted Denial of Service in Visual Studio Search
- 50 Bytes of Code That Took 4 GB to Compile
Windows Performance Toolkit (profiling the profiler!):
- Xperf Symbol Loading Pitfalls
- Slow Symbol Loading in Microsoft’s Profiler, Take Two
- Profiling the profiler: working around a six minute xperf hang
Windows:
- Delays in login to Windows due to thread rank – what outranks thread priority
- O(n^2), again, now in WMI
- Making VirtualAlloc Arbitrarily Slower – excessive CPU usage
- Hidden Costs of Memory Allocation – excessive CPU usage
- Taskbar Latency and Kernel Calls – excessive CPU usage (Windows bug)
- O(n^2) in CreateProcess – CFG causing problems again, excessive CPU usage (Windows bug, now fixed)
- A Not-Called Function Can Cause a 5X Slowdown – lock contention during process shutdown, caused by loading the wrong DLL (Windows quirk, triggered by llvm tests)
- Making Windows Slower Part 2: Process Creation – O(n^2) in CreateProcess due to Application Verifier
- 24-core CPU and I can’t type an email (part one) – lock contention during process shutdown (CFG, service workers, v8, WMI – it’s got everything, but it’s mostly Windows bugs)
- Making Windows Slower Part 1: File Access – slowing down Chrome builds with large notification buffers (Windows bug, now fixed)
- 24-core CPU and I can’t move my mouse – lock contention during process shutdown (Windows bug, now fixed)
- 63 Cores Blocked by Seven Instructions – NTFS lock contention bringing a build machine to its knees (Windows bug)
- Arranging Invisible Icons in Quadratic Time – this demonstrates how to use UI Delays to find where a hang is happening, CPU Usage (Precise) to prove that it’s a busy hand, and then CPU Usage (Sampled) to see where time is being spent. And then some surprisingly simple work to prove that it’s a quadratic algorithm.
Windows Live Photo Gallery:
- Windows Live Photo Gallery—Poor Performance Peculiarities (xperfview used for analysis, but concepts are still solid)
- Fixing another Photo Gallery performance bug
Western Digital driver (initially thought to be Windows):
- Windows Slowdown, Investigated and Identified
-
Windows Slowdown, Investigated, Identified, and Now Fixed
Miscellaneous:
- Faster Fractals Through Better Scheduling
- PowerPoint Poor Performance Problem
- Defective Heat Sinks Causing Garbage Gaming
Other people’s ETW investigation write-ups:
Obsolete posts
Some of the blog posts are now completely obsolete and are listed here only for historical interest:
- Xperf Analysis Basics – obsolete or covered elsewhere
- Xperf Basics: Recording a Trace, replaced by Xperf Basics: Recording a Trace (the easy way) which was then replaced by Xperf Basics: Recording a Trace (the ultimate easy way) – third time’s the charm
- Xperf for Excess CPU Consumption – replaced by Xperf for Excess CPU Consumption: WPA edition
- The New Xperf is Here! – replaced by Xperf Basics: Recording a Trace (the ultimate easy way)
- The New WPA Xperf Trace Viewer–New Bugs and Old – the reported bugs are generally fixed
- Summarizing Xperf CPU Usage with Flame Graphs – WPA 10.0.14393 has built-in flame graphs which are covered here
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Did you use logman? Is it better/worse than xperf? https://technet.microsoft.com/en-gb/library/cc753820.aspx?f=255&MSPPError=-2147217396
I don’t think logman is necessarily better or worse than xperf but I don’t think it can do the things that I do with xperf, so it is of little interest to me. Disclaimer: I’m not a logman expert, but I think this is true.
TL;DR – UIforETW/xperf/WPA can work miracles and I explain how to do this in this blog. logman? Dunno.
Not that it can do something different, but on my W10 installation it came with the system, C:\Windows\System32\logman.exe. Basically, if you install something on user system, looks like it is much better to run logman as an events watchman for your app
Unfortunately I don’t *think* that logman has the same capabilities. Pity.
Hi Bruce, awesome work! Is there a place for RFEs? In particular, it would be great to be able to change the “trace to memory” window as well as specify the length of time before a trace is automatically saved to disk and/or stopped. Thanks!
Feel free to create issue suggestions at https://github.com/google/UIforETW/issues
Configuring the memory used and the auto-trace elapsed time has been suggested, but such changes must be made carefully to avoid giving users unnecessary foot-guns. “It just works” must continue to be as true as possible. That is, configuration is reasonable as long as it adds value without undue complexity or user risk.
Thanks. The complexity issue I understand but your point of view on risk seems overly cautious. As someone who has programmed in C/C++ for over 25 years, I have no lower extremities left to shoot! In my experience, a high amount of configurability is suitable for all but the most skittish, particularly when the *defaults* just work. In debugging performance and other issues, exploration is part of learning the ropes and I wouldn’t limit configurability unnecessarily in order to keep safe a small percentage of users that would try to do silly things on production systems. Yes I understand that having more configuration options multiplies the bug surface area and maintenance costs but I think that most users willing to experiment with advanced functionality would also be willing to help debug and improve those features, directly or indirectly. EOP (End of Pitch).
I don’t disagree. Having it work out-of-the-box is most important. Having the configuration options as uncluttered as possible is also important, since every option that is added makes the remaining options harder to find. But I don’t think we’re really disagreeing in any meaningful way.
> most users willing to experiment with advanced functionality would
> also be willing to help debug and improve those features
Well, the great thing about UIforETW being open source is that they can just grab a copy, change the constants, and party-on-Garth!
https://github.com/google/UIforETW/releases/download/v1.48/etwpackage1.48.zip
shows a malware in your file.
https://www.virustotal.com/en/file/896554acbe3983cd69e100f1e5867c8cfcc30510567e297c843c96ed6e11d986/analysis/
Sigh… I’m sure that file doesn’t contain malware, but it isn’t signed which can make AV software suspicious. I’ll add it to my list of files to sign which should resolve this for the next release.
Everything should be signed now, which should avoid malware warnings.
I think another slowdown is on very large source files. If the function(s) being debugged can be migrated to smaller source files, its debugs faster. This was observed on a single source file that was 20K+ lines long.
Hi Bruce, adore your blog!
Do you know, is it possible to collect PMInterrupt stacks somehow?
I’ve found the event in https://github.com/google/UIforETW/blob/master/UIforETW/StackWalkFlags.txt,
but didn’t manage to collect stacks for it:(
I think that ETW handles PMC counters by recording their values during context switches. If so then recording PMC interrupt stacks is meaningless. It’s an idea that’s only applicable if the interrupts fire after a certain number of events. But, I may be misunderstanding. I’d recommend sharing what you’ve tried so others can learn from what did or did not work.
Hello,
Thanks for all your training material for WPA/WPR. I’m trying to learn more about Windows and Services in particular. I’m wondering how you would go about using WPA to find out what triggered a particular service to start? I know how to isolate a service into it’s own svchost.exe and I can zoom into where the service starts and I see that services.exe is the process that starts it, but I don’t know how to go about finding out who/what called upon the services.exe to actually start it up.
Thanks again for all your material!
Hi Bruce,
Please, Is it suitable to launch multiple apps on Windows then record them with WPR, also after a while, launch other apps and so on (every single time e.g. every 8min), then analyze them with WPA. will I get low-performance issues like low JIT compilation, memory consumption, etc? which apps are suitable for that?. Thank you.
I’m not sure exactly what you are trying to do but I have found WPR/ETW to be suitable for investigating lots of performance issues. I prefer UIforETW for recording the traces, but I think WPR does have a few advantages.
You say “every 8 min” and I would only caution you against recording long traces. ETW traces can be enormous and this then makes them cumbersome. I try to make most of my ETW traces be 20-60 seconds long. There are few issues that become easier to investigate through having a longer time period recorded.
I’m trying to identify Memory leak, looking for an increasing trend over a long period of time, Which means the application committing memory (referred to a private bytes) and releasing only small portions, and over a period of time it continue to accumulate Memory.
I’m asking to detect this pattern of Memory consumption Practically.
Thanks
Slow memory leaks can be difficult. The default trace settings record memory allocated with VirtualAlloc which can be enough. Go to Settings and enable VirtualAlloc stacks always to get more information (and then view the VirtualAlloc data, with stacks, focusing on those with Type==AIFO)
Or, you can use heap snapshots. I’ve used that to record every outstanding allocation from Chrome’s browser process over a two week period: https://randomascii.wordpress.com/2019/10/27/heap-snapshots-tracing-all-heap-allocations/
Heap snapshots are great but only work if you are leaking heap memory. vmmap can be used to determine that.
Is it suitable to do it just in WPR/WPA toolkit? or I have to deal with your mentioned tools in Github? because I don’t have much experience to deal with what you explain in Github, maybe just through the tutorial!
Also, please, is there a way to detect that Memory leak while launching multiple apps, not specific ones? Thanks!
I don’t know what allocation data WPR records. UIforETW records VirtualAlloc data across all processes with optional call stacks which allows for investigating memory leaks in multiple processes. Some of the concepts in the Heap Tracing and Heap Snapshots articles are relevant, in particularly the Type column and the AIFO type. However you will have to use the Virtual Alloc Commit LifeTimes table, found under Graph Explorer-> Memory.
Hello Bruce,
How can I design and Implement an ETW-based Windows system Performance testing tool and give it a name, that system can implement a process collecting, analyzing, and visualizing various events that occur in the Windows system kernel by means of event tracking, and is used to detect the performance that occurs during system operations, and to make it quickly locate the bottleneck and improve the efficiency of the system operations.? I hope if there is a tutorial for this work. Thanks.
Collecting? wpr or UIforETW
Visualizing? WPA
Quickly locate the bottleneck and improve the efficiency of system operations? Read my blog posts and other sources, practice, learn, refine, and repeat.
The information is there. If you are hoping for an automatic system to detect and fix performance bugs then you are out of luck, but manual detection and fixing is possible and I do it all the time.
Thank you for the reply,
sorry, I mean to design that ETW diagnostic tool in .NET
For recording and visualizing traces you shouldn’t be worrying about the language or runtime used to create the tool. For analysis it turns out that .NET is the preferred choice. I blogged about how to do trace analysis in C# earlier this year:
https://randomascii.wordpress.com/2020/01/05/bulk-etw-trace-analysis-in-c/
However, programmatic trace analysis is not a panacea. It can look for known patterns, and summarize known types of data, but the most interesting performance bugs are novel and require human ingenuity to understand.
I recommend reading my many blog posts on these topics and then asking more specific questions.
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hi Bruce
when i set the tracing to file the tool stops tracing after 5 minute. i need the whole story from the start, the circular buffer tracing is not enough. i get the message: “Tracing to disk ran excessively long. Auto-saving and stopping.”
The size of the file is between 300-500MB. How can I configure the max file size, or the time period of the trace?
thanks,
np
A 300-500 MB trace is already quite long and will be unwieldy to analyze. If you want a longer trace you can either use the batch files that ship with UIforETW to control tracing (modify them to suit your needs, etwrecord.bat is probably a good starting point) or you can download the UIforETW source and modify or remove the limit. That said, traces longer than five minutes are often more trouble than they are worth.
Here’s the relevant bit of code (found by searching for the message in this file):
https://github.com/google/UIforETW/blob/main/UIforETW/UIforETWDlg.cpp#L1488