Maoni Stephens

Finalization implementation details

September 16th, 2019

Years ago I wrote a document on making finalization scanning concurrent. At the time there was an internal team that was using finalization as a way to resurrect objects and putting them back in their cache. While we’ve always advised to folks that finalization was for releasing native resources I couldn’t fault this team for using it the

GC Perf Infrastructure – Part 0

September 9th, 2019

In this blog entry and some future ones I will be showing off functionalities that our new GC perf infrastructure provides. Andy and I have been working on it (he did all the work; I merely played the consultant role). We will be open sourcing it soon and I wanted to give you some examples of using it and you can add these to your repertoire o

A portable way to get GC events in process and no admin privilege with 10 lines of code (and ability to dynamically enable/disable events)

April 8th, 2019

I’ve been talking about doing managed heap performance analysis with ETW events for ages because ETW is just such a powerful tool. It has a well defined format so many components, from kernel modes to user mode ones, all emit ETW events which means you can have tools that just know how to parse the event format and correlate them. At Microso

Making CPU configuration better for GC on machines with > 64 CPUs

April 3rd, 2019

If you are running Windows on a machine with > 64 CPUs, you’ll need to use this feature called the CPU groups for your process to be able to use more than 64 CPUs. At some point in the far distant past, people thought having more than 64 processors on a machine was inconceivable so they used a 64-bit number for the processor mask. And when 6

Running with Server GC in a Small Container Scenario Part 1 – Hard Limit for the GC Heap

February 4th, 2019

I’ve checked in 2 configs related to specifying a hard limit for the GC heap memory usage so I wanted to describe them and how they are intended to be used. Feedback would be greatly appreciated. In order to talk about the new configs it’s important to understand what consists of the memory usage in a process. When it comes to memory the

Running with Server GC in a Small Container Scenario Part 0

November 16th, 2018

This week I was able to get some time to work on the container stuff with low memory limits. As many of you have expressed your dissatisfaction on how Server GC behaves with low memory limit specified on containers on github, I have to apologize that I am just doing this now. Really sorry that some of you guys have to suffer through this thus

You Should Never See This Callstack in Production

October 9th, 2018

A customer who just experienced some server outage asked us for help as they thought it was due to some very long GC pauses. I thought this diagnostics exercise might be useful for other folks as well so I am sharing it with you. We had them collect a GCCollectOnly trace which showed there were some very long induced gen2 blocking GCs. And th

Middle Ground between Server and Workstation GC

October 2nd, 2018

A long time ago I wrote about using Workstation GC on server applications when you have many instances of your server app running on the same machine. By default Server GC will treat the process as owning the machine so it uses all CPUs to do the GC work. More and more folks find themselves in a situation where they might have a few active ins

Get This Fantastic Book about .NET Memory Management!

September 17th, 2018

If you are reading my blog chances are you care about .NET memory performance, most likely a lot. Our GC source is on github for anyone to look at. If you are curious enough, you could absolutely learn a lot about our GC by cloning our coreclr repo, building it, and stepping through the GC code under a debugger (that's how I really learned de

GLAD Part 2

September 9th, 2018

2 years ago I had a blog entry to introduce the GLAD (GC Latency Analysis and Diagnostics) library which provides much more insight into the GC heap performance than perf counters and takes care of interpreting raw GC ETW events so our users don't have to do that work themselves. Since then I have not heard too much usage from our customers :P