Tracing .NET Core on Linux with USDT and BCC

Sunday, April 2, 2017

In my last post, I lamented the lack of call stack support for LTTng events in .NET Core. Fortunately, being open source, this is somewhat correctable -- so I set out to produce a quick-and-dirty patch that adds USDT support for CoreCLR's tracing events. This post explores some of the things that then become possible, and will hopefully become available in one form or another in CoreCLR in the future. Very Brief USDT Primer USDT (User Statically Defined Tracing) is a lightweight approach for embedding static trace markers into user-space libraries and applications. I've taken a closer look a year ago when...

Tracing Runtime Events in .NET Core on Linux

Thursday, March 30, 2017

After exploring the basic profiling story, let's turn to ETW events. On Windows, the CLR is instrumented with a myriad of ETW events, which can be used to tackle very hard problems at runtime. Here are some examples of these events: Garbage collections Assembly load/unload Thread start/stop (including thread pool threads) Object allocations Exceptions thrown, caught, filtered Methods compiled (JIT) By collecting all of, or a subset of, these events, you can get a very nice picture of what your .NET application is doing. By combining these with Windows kernel events for CPU sampling, file accesses, process creations and more -- you have a fairly...

Profiling a .NET Core Application on Linux

Monday, February 27, 2017

In the same vein of my previous post on analyzing core dumps of .NET Core applications on Linux, let's take a look at what it takes to do some basic performance profiling. When starting out, here are a few things I wrote down that would be nice to do: CPU profiling (sampling) to see where the CPU bottlenecks are Grabbing stacks for interesting system events (file accesses, network, forks, etc.) Tracing memory management activity such as GCs and object allocations Identifying blocked time and the block and wake-up reasons With this task list in mind, let's get started! Collecting Call Stacks of .NET Core Processes Generally speaking, a...
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Analyzing a .NET Core Core Dump on Linux

Sunday, February 26, 2017

Recently, I had to open a core dump of a .NET Core application on Linux. I thought this walkthrough might be useful if you find yourself in the same boat, because, to be quite honest, I didn't find it trivial. Configure Linux to Generate Core Dumps Before you begin, you need to configure your Linux box to generate core dumps in the first place. A lot of distros will have something preconfigured, but the simplest approach is to just put a file name in the /proc/sys/kernel/core_pattern file: # echo core > /proc/sys/kernel/core_pattern Additionally, there's a system limit maximum size for the generated core file. ulimit -c unlimited removes...

Wrapping Up TechDays Sweden 2015

Thursday, October 22, 2015

This is my second TechDays this year--I've had the pleasure of visiting the Netherlands and now also Sweden to speak at TechDays on a variety of topics. Both events had quite a special atmosphere with a lot of activity, a lot more session slots than usual at software conferences, and a great selection of international speakers (except for your humble servant, of course). Even though most talks were in languages I don't understand, I really enjoyed my time. But I'm guessing you're here because you want to put your hands on materials from my two talks--so here they are, without...
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