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Category Archives: xperf
Windows Performance Analyzer, From Store or SDK
ETW is the best way to analyze performance on Windows, and Windows Performance Analyzer (WPA) has been the preferred tool for analyzing ETW traces for ten years now, generally obtained either by running UIforETW or by getting it from the … Continue reading
Finding Windows HANDLE leaks, in Chromium and others
Three years ago I found a 32 GB memory leak caused by CcmExec.exe failing to close process handles. That bug is fixed, but ever since then I have had the handles column in Windows Task Manager enabled, just in case … Continue reading
Posted in Bugs, Code Reliability, Investigative Reporting, uiforetw, xperf
Tagged handles, leaks
20 Comments
What Outranks Thread Priority?
This investigation started, as so many of mine do, with me minding my own business, not looking for trouble. In this case all I was doing was opening my laptop lid and trying to log on. The first few times … Continue reading
Posted in Investigative Reporting, Performance, uiforetw, xperf
Tagged laptops, standby, Windows
7 Comments
Bulk ETW Trace Analysis in C#
ETW traces record a wealth of information about how a Windows system is behaving. When analyzing a new and unknown problem there is no replacement for loading the trace into WPA and following the clues to a solution. The thrill … Continue reading
O(n^2), again, now in WMI
I recently hit some multi-minute delays on my workstation. After investigating I found that the problem was due to a lock being held for five minutes, and during that time the lock-holder was mostly just spinning in a nine-instruction loop. … Continue reading
Posted in Investigative Reporting, Programming, Quadratic, Rants, uiforetw, xperf
Tagged complexity, ETW, O(n^2), performance, WMI
23 Comments
Heap Snapshots–Tracing All Heap Allocations
I’ve recently started using heap snapshots on Windows to track heap allocations. I was able to use heap snapshots to record call stacks for all outstanding allocations in Chrome’s browser process over a full two weeks, letting me account for … Continue reading
Posted in Documentation, Performance, Programming, uiforetw, xperf
Tagged heap snapshots, memory
22 Comments
63 Cores Blocked by Seven Instructions
I seem to have a habit of writing about super powerful machines whose many cores are laid low by misuse of locks. So. Yeah. It’s that again. But this one seems particularly impressive. I mean, how often do you have … Continue reading
Posted in Investigative Reporting, Performance, Programming, Quadratic, uiforetw, xperf
Tagged ETW, ntfs, wpa
12 Comments
O(n^2) in CreateProcess
So many possible introductions to this one: Windows 7: Sheesh, I sure am slow at creating processes Windows 10: Hold my beer… Or how about: A) How long does CreateProcess take on Windows? B) How long would you like it … Continue reading
When Your Profiler Lies
Last week I wrote about the performance consequences of inadvertently loading gdi32.dll into processes that are created and destroyed at very high rates. This week I want to share some techniques for digging deeper into this behavior, and the odd … Continue reading
Posted in Investigative Reporting, Performance, Programming, uiforetw, xperf
Tagged GDI, process shutdown, UserCrit
12 Comments
Random ASCII - tech blog of Bruce Dawson 