From 88b5ff75f543acac18f6d8b0582980010bd831c9 Mon Sep 17 00:00:00 2001
From: Jason Tibbitts <j@tib.bs>
Date: Nov 01 2021 22:54:35 +0000
Subject: [PATCH 1/2] Remove outdated SMP language


Since most everything is SMP these days, clean up the language in the
Parallel Make section.

---

diff --git a/guidelines/modules/ROOT/pages/index.adoc b/guidelines/modules/ROOT/pages/index.adoc
index 3ea19f4..323ec05 100644
--- a/guidelines/modules/ROOT/pages/index.adoc
+++ b/guidelines/modules/ROOT/pages/index.adoc
@@ -2331,18 +2331,8 @@ Whenever possible, invocations of `+make+` should be done as
 %make_build
 ....
 
-This generally speeds up builds and especially on SMP machines.
-
-Do make sure, however, that the package builds cleanly this way
-as some make files do not support parallel building.
-Therefore you should consider adding
-
-....
-%_smp_mflags -j3
-....
-
-to your `+~/.rpmmacros+` file -- even on UP machines --
-as this will expose most of these errors.
+This will pass appropriate flags to build in parallel
+and set useful verbosity flags.
 
 == Scriptlets
 

From f98fddec7fd2fd1302f41524631015b172dd6d59 Mon Sep 17 00:00:00 2001
From: Jason Tibbitts <j@tib.bs>
Date: Nov 01 2021 23:37:10 +0000
Subject: [PATCH 2/2] Document %constrain_build


---

diff --git a/guidelines/modules/ROOT/pages/index.adoc b/guidelines/modules/ROOT/pages/index.adoc
index 323ec05..c690e40 100644
--- a/guidelines/modules/ROOT/pages/index.adoc
+++ b/guidelines/modules/ROOT/pages/index.adoc
@@ -2334,6 +2334,31 @@ Whenever possible, invocations of `+make+` should be done as
 This will pass appropriate flags to build in parallel
 and set useful verbosity flags.
 
+=== Constraining Build Parallelism
+
+The `%constrain_build` macro can be used near the top of the spec file
+to constrain build parallelism.
+When called with no arguments, the CPU count will be reduced to one.
+The `+-c+` option will set the CPU count to a given value:
+
+  %constrain_build -c 4
+
+will force the build to use at most four CPUs.
+
+The `+-m+` option allows you to specify the amount of memory
+in megabytes which a single build thread takes.
+The macro will divide the total amount of memory in the system
+by this value and set the CPU count to the result (rounded down).
+On a machine with 32GB of memory:
+
+  %constrain_build -m 10000
+
+will set the CPU count to three.
+
+This macro will influence anything which considers the value of
+`%_smp_build_ncpus` including
+`%make_build`, `%cmake_build` and `%meson_build`.
+
 == Scriptlets
 
 Great care should be taken when using scriptlets in Fedora packages.