build-parallelism

MSBuild Parallelism Model

• /maxcpucount (or -m): number of worker nodes (processes)
• Default: 1 node (sequential!). Always use -m for parallel builds
• Recommended: -m without a number = use all logical processors
• Each node builds one project at a time
• Projects are scheduled based on dependency graph

Project Dependency Graph

• MSBuild builds projects in dependency order (topological sort)
• Critical path: longest chain of dependent projects determines minimum build time
• Bottleneck: if project A depends on B, C, D and B takes 60s while C and D take 5s, B is the bottleneck
• Diagnosis: replay binlog to diagnostic log with performancesummary and check Project Performance Summary — shows per-project time; grep for node.*assigned to check scheduling
• Wide graphs (many independent projects) parallelize well; deep graphs (long chains) don't

Graph Build Mode (/graph)

• dotnet build /graph or msbuild /graph