treewide: drop -l$NIX_BUILD_CORES

Passing `-l$NIX_BUILD_CORES` improperly limits the overall system load.

For a build machine which is configured to run `$B` builds where each
build gets `total cores / B` cores (`$C`), passing `-l $C` to make will
improperly limit the load to `$C` instead of `$B * $C`.

This effect becomes quite pronounced on machines with 80 cores, with
40 simultaneous builds and a cores limit of 2. On a machine with this
configuration, Nix will run 40 builds and make will limit the overall
system load to approximately 2. A build machine with this many cores
can happily run with a load approaching 80.

A non-solution is to oversubscribe the machine, by picking a larger
`$C`. However, there is no way to divide the number of cores in a way
which fairly subdivides the available cores when `$B` is greater than
1.

There has been exploration of passing a jobserver in to the sandbox,
or sharing a jobserver between all the builds. This is one option, but
relatively complicated and only supports make. Lots of other software
uses its own implementation of `-j` and doesn't support either `-l` or
the Make jobserver.

For the case of an interactive user machine, the user should limit
overall system load using `$B`, `$C`, and optionally systemd's
cpu/network/io limiting features.

Making this change should significantly improve the utilization of our
build farm, and improve the throughput of Hydra.

1 files changed, 3 insertions, 3 deletions

diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index f0fcb30451dd8..62f9121d73d6b 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -1100,7 +1100,7 @@ buildPhase() {
         # Old bash empty array hack
         # shellcheck disable=SC2086
         local flagsArray=(
-            ${enableParallelBuilding:+-j${NIX_BUILD_CORES} -l${NIX_BUILD_CORES}}
+            ${enableParallelBuilding:+-j${NIX_BUILD_CORES}}
             SHELL=$SHELL
             $makeFlags "${makeFlagsArray[@]}"
             $buildFlags "${buildFlagsArray[@]}"
@@ -1139,7 +1139,7 @@ checkPhase() {
         # Old bash empty array hack
         # shellcheck disable=SC2086
         local flagsArray=(
-            ${enableParallelChecking:+-j${NIX_BUILD_CORES} -l${NIX_BUILD_CORES}}
+            ${enableParallelChecking:+-j${NIX_BUILD_CORES}}
             SHELL=$SHELL
             $makeFlags "${makeFlagsArray[@]}"
             ${checkFlags:-VERBOSE=y} "${checkFlagsArray[@]}"
@@ -1273,7 +1273,7 @@ installCheckPhase() {
         # Old bash empty array hack
         # shellcheck disable=SC2086
         local flagsArray=(
-            ${enableParallelChecking:+-j${NIX_BUILD_CORES} -l${NIX_BUILD_CORES}}
+            ${enableParallelChecking:+-j${NIX_BUILD_CORES}}
             SHELL=$SHELL
             $makeFlags "${makeFlagsArray[@]}"
             $installCheckFlags "${installCheckFlagsArray[@]}"