diff --git a/memory-constraints.macros b/memory-constraints.macros
index 8cbd51e..5f6ec13 100644
--- a/memory-constraints.macros
+++ b/memory-constraints.macros
@@ -4,3 +4,23 @@
 # crazy magic in order to make sure it is most of the time building
 # rather than just giving you OOM
 #
+
+# m: memory limit in MBs per core; default is 1000
+%limit_build(m:) \
+    _threads="`/usr/bin/getconf _NPROCESSORS_ONLN`"
+    _core_memory="%{-m:%{-m*}}%{!-m:1000}"
+    echo "Available memory:" \
+    cat /proc/meminfo \
+    echo "System limits:" \
+    ulimit -a \
+    echo "System jobs: $_threads" \
+    if test "$_threads" -gt 1 ; then \
+        mem_per_process="$_core_memory" \
+        max_mem=$(awk '/MemTotal/ { print $2 }' /proc/meminfo) \
+        max_jobs="$(($max_mem / $mem_per_process))"
+        test "$_threads" -gt "$max_jobs" && $_threads="$max_jobs" && echo "Warning: Reducing number of jobs to $max_jobs because of memory limits" \
+        test "$_threads" -le 0 && $_threads=1 && echo "Warning: Do not use the parallel build at all becuse of memory limits" \
+    fi \
+    %global jobs $_threads
+    %global _smp_mflags -j$_threads
+    %{nil}
diff --git a/memory-constraints.spec b/memory-constraints.spec
index 45ea297..5638594 100644
--- a/memory-constraints.spec
+++ b/memory-constraints.spec
@@ -25,6 +25,7 @@ Group:          Development/Tools/Building
 URL:            https://www.opensuse.org/
 Source0:        %{name}.macros
 BuildRequires:  rpm
+Requires:       awk
 BuildArch:      noarch
 
 %description