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ocaml: enable parallel building

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Enable parallel building for ocaml-4.08 and above. tested as:

    $ nix build -f. ocaml-ng.ocamlPackages_{4_{00_1,01_0,02,03,04,05,06,07,08,09,10,11,12,13},latest}.ocaml --keep-going

ocaml build system supports parallel building, but but for multiple
top-level targets at the same time as it usually spawns subprocess
$(MAKE) that occasionally conflict with one another. To work it around
we use tiny Makefile with a single rule that calls top-level targets
sequentially as makefile calls:

    nixpkgs_world_bootstrap_world_opt:
       $(MAKE) world
       $(MAKE) bootstrap
       $(MAKE) world.opt

On a 16-core machine ocaml-4.12 build speeds up from 6m55s to 1m35s.

Releases 4_00_1, 4_01_0, 4_04 and 4_05 still have some race in them.
Thus this change enables parallel builds only for ocaml-4.06 and above.

Adapted from #142723

upstreams's CI tests the parallel makefile: https://github.com/ocaml/ocaml/issues/10235#issuecomment-782100584
The limit was chosen to be 4.08 because it was released in 2019, not too
long before the above link.
This commit is contained in:
Sergei Trofimovich 2021-10-24 09:39:21 +01:00 committed by Guillaume Girol
parent e20385a2e9
commit 238d634e4b
2 changed files with 28 additions and 1 deletions
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16
pkgs/development/compilers/ocaml/Makefile.nixpkgs Normal file
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@ -0,0 +1,16 @@
# ocaml build system does not allow for parallel building of some
# top-level targets like 'world', 'bootstrap', 'world.opt' as
# then spawn '$(MAKE) all' subprocesses that conflict among each
# other. But we would still like to run each target in parallel
# individually. This file defines such entry points.
# Re-export all existing phases to make 'make install' work as is.
include Makefile
nixpkgs_world:
$(MAKE) world
nixpkgs_world_bootstrap_world_opt:
$(MAKE) world
$(MAKE) bootstrap
$(MAKE) world.opt

13
pkgs/development/compilers/ocaml/generic.nix
View File

@ -68,7 +68,18 @@ stdenv.mkDerivation (args // {
# x86_64-unknown-linux-musl-ld: -r and -pie may not be used together
hardeningDisable = lib.optional (lib.versionAtLeast version "4.09" && stdenv.hostPlatform.isMusl) "pie";
buildFlags = [ "world" ] ++ optionals useNativeCompilers [ "bootstrap" "world.opt" ];
# Older versions have some race:
# cp: cannot stat 'boot/ocamlrun': No such file or directory
# make[2]: *** [Makefile:199: backup] Error 1
enableParallelBuilding = lib.versionAtLeast version "4.08";
# Workaround lack of parallelism support among top-level targets:
# we place nixpkgs-specific targets to a separate file and set
# sequential order among them as a single rule.
makefile = ./Makefile.nixpkgs;
buildFlags = if useNativeCompilers
then ["nixpkgs_world_bootstrap_world_opt"]
else ["nixpkgs_world"];
buildInputs = optional (!lib.versionAtLeast version "4.07") ncurses
++ optionals useX11 [ libX11 xorgproto ];
propagatedBuildInputs = optional spaceTimeSupport libunwind;