On Thu, Jun 18, 2026 at 3:31 PM Ludovic Courtès <[email protected]> wrote:
>
> Hi!
>
> Gabriel Wicki <[email protected]> skribis:
>
> > Brooding over packaging the EDA tool naja and its fork of some `slang`
> > package I noticed that the build was *very* slow. Checking `top` I
> > figured object files are compiled serially. A quick search produced¹
> > and wow, build time is N-core times faster now. Which raises the
> > question: is it possible that cmake-build-system does not set
> > CMAKE_BUILD_PARALLEL_LEVEL by default?
>
> The ‘build’ phase in ‘guix/build/cmake-build-system.scm’ invokes ‘make’
> with ‘-jN’ by default, so it’s building things in parallel (respecting
> the ‘--cores’ option passed to ‘guix-daemon’ or ‘guix’).
The cmake-build-system now uses cmake to build (ninja is faster than
make and can be enabled with #:generator "Ninja"):
(define* (build #:key (make-flags '()) (parallel-build? #t)
#:allow-other-keys)
(apply invoke "cmake"
`("--build"
"."
,@(if parallel-build?
`("-j" ,(number->string (parallel-job-count)))
;; When unset CMake defers to the build system.
'("-j" "1"))
;; Pass the following options to the native tool.
"--"
,@(if parallel-build?
;; Set load average limit for Make and Ninja.
`("-l" ,(number->string (total-processor-count)))
'())
,@make-flags)))
