Intermittent 6–7h MSBuild run vs 1.5h rerun(binlog attached)

[yzsara]

Hi
We’re investigating an intermittent MSBuild performance issue where, under identical conditions and without source or environment changes, a build occasionally takes 6–7 hours, while an immediate re-run completes in ~1.5 hours.

Key observations:

Same source, machine, MSBuild version, and command

Real-time AV scanning disabled for source, obj/bin, and NuGet paths

Local disk only (no network or synced paths)

No custom signing, scripts, or external tools

NuGet restore completes before build

What we found:

Comparing binlogs shows very heavy obj activity in the slow build

Slow build: ~127k log entries under obj

Normal build: ~27k log entries
GitHub doesn’t allow .binlog uploads!

[JanProvaznik]

You can upload .binlog files by first zipping them