How to build dotnet runtime without FEATURE_EVENT_TRACE (liblttng)

[harisokanovic]

The dotnet9 runtime published on dot.net don't seem to use liblttng - i.e. as if FEATURE_EVENT_TRACE is disabled - but my local builds of dotnet/dotnet from Github have it on.

What's the best way to configure local builds to disable liblttng?

Moreover, how does one reproduce the same configuration and binaries published on dot.net?

I'm asking these questions because liblttng-ust-common.so is masking a load-time performance issue. The issue shows when using the published runtime downloaded from dot.net but not on local builds where libcoreclr.so loads liblttng-ust-common.so. I would like to test a fix before publishing a PR, but I don't know how to configure my local build to match published binaries.

---

lttng symbols not present in published binary:

wget https://dot.net/v1/dotnet-install.sh -O dotnet-install.sh
chmod 0755 dotnet-install.sh
sudo ./dotnet-install.sh --channel 9.0 --install-dir /usr/share/dotnet
readelf -a /usr/share/dotnet/shared/Microsoft.NETCore.App/9.0.0-preview.7.24405.7/libcoreclr.so 2>&1 | grep lttng | wc -l
0

but present in local builds under default configuration:

git clone https://github.com/dotnet/dotnet
./prep-source-build.sh
./build.sh -sb --clean-while-building
mkdir xxx
cd xxx
tar -xf ../artifacts/assets/Release/dotnet-sdk-9.0.100-rc.1.24415.1-ubuntu.22.04-arm64.tar.gz
readelf -a ./shared/Microsoft.NETCore.App/9.0.0-rc.1.24414.5/libcoreclr.so 2>&1 | grep lttng | wc -l
1807

[harisokanovic]

See runtime issue 106722 for more info about the issue. I also published PR 106724 with a potential fix.