topology: cmake: build topologies in parallel, add -s to force sequen…

[ujfalusi]

…tial

alsatplg custom commands were marked USES_TERMINAL. With the Ninja generator this places them in the single-job "console" pool, which serializes every topology build regardless of the -j value passed to ninja. Building all 579 topologies therefore never used more than one core, even on a many-core machine.

Drop USES_TERMINAL by default so Ninja can run alsatplg invocations in parallel, controlled by a new TPLG_SEQUENTIAL_BUILD CMake option (default OFF).

Add a -s flag to build-tools.sh that sets TPLG_SEQUENTIAL_BUILD=ON, to restore the old, easier to debug one-at-a-time behavior when needed. It updates the CMake cache in place, so it also works on an existing incremental build tree without deleting it.

Results
Sequential (before this patch or with -T -s with this patch): ./scripts/build-tools.sh -T -s 19.30s user 2.34s system 99% cpu 21.817 total

Parallel:
rm -rf tools/build_tools; time ./scripts/build-tools.sh -T ./scripts/build-tools.sh -T 33.79s user 3.52s system 986% cpu 3.783 total

The build time changes from ~22s to ~4s

[Copilot]

Pull request overview

This PR enables parallel topology builds by default while adding an opt-in sequential debugging mode.

Changes:

• Makes topology command serialization conditional.
• Adds TPLG_SEQUENTIAL_BUILD and the build-tools.sh -s option.
• Supports updating existing build trees.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Summary	Final comments
tools/topology/CMakeLists.txt	Controls topology build parallelism.	None
scripts/build-tools.sh	Adds sequential-build configuration and CLI handling.	Document -s in scripts/README.md (nit, 2 votes). Reset the cached option when -s is omitted (moderate, 4 votes).

Suppressed comments (1)

tools/topology/CMakeLists.txt:8

• The new public build control is missing from the repository's existing topology documentation: scripts/README.md:45-55 lists the build-tools.sh options but omits -s, and tools/topology/README.md:14-22 does not explain the sequential/parallel CMake option. Please update those READMEs so users can discover and understand this behavior.

option(TPLG_SEQUENTIAL_BUILD "Build topologies one at a time (for debugging)" OFF)

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[ujfalusi]

Changes since v1:

• Update the README.md
• always update the parallel/sequential build type

[lyakh]

@ujfalusi (mostly) out of curiosity - IIUC this "19.30s user 2.34s system 99% cpu 21.817 total" is the time output in your case. I tried both shell builtin time and /bin/time and it isn't the default output of any of them on my systems. But it does look like the "total" value is the wall clock time, which in the first case is mostly just a sum of user and system (as expected), while in the latter case it's much smaller. Interesting, that the user time increased by more than 50%: "33.79s user 3.52s system 986% cpu 3.783 total"

[ujfalusi]

@ujfalusi (mostly) out of curiosity - IIUC this "19.30s user 2.34s system 99% cpu 21.817 total" is the time output in your case.

This is zsh's built in time, with bash:
sequential (old way):

real    0m22.287s
user    0m19.724s
sys     0m2.387s

parallel:

eal    0m4.126s
user    0m34.188s
sys     0m3.573s

I tried both shell builtin time and /bin/time and it isn't the default output of any of them on my systems. But it does look like the "total" value is the wall clock time, which in the first case is mostly just a sum of user and system (as expected), while in the latter case it's much smaller. Interesting, that the user time increased by more than 50%: "33.79s user 3.52s system 986% cpu 3.783 total"

ref: https://unix.stackexchange.com/questions/562650/how-can-i-make-the-output-of-time-in-zsh-be-like-bash