build/ops: rpm: make lowmem_builder code much smarter

Signed-off-by: Nathan Cutler <ncutler@suse.com>
Signed-off-by: Tomas Chvatal <tchvatal@suse.com>

ceph.spec.in

@@ -138,6 +138,9 @@ BuildRequires:	make
 BuildRequires:	parted
 BuildRequires:	perl
 BuildRequires:	pkgconfig
+%if %{with lowmem_builder}
+BuildRequires:  procps
+%endif
 BuildRequires:	python
 BuildRequires:	python-devel
 BuildRequires:	python-nose
@@ -797,18 +800,42 @@ export CPPFLAGS="$java_inc"
 export CFLAGS="$RPM_OPT_FLAGS"
 export CXXFLAGS="$RPM_OPT_FLAGS"
 
-env | sort
-
+# Parallel build settings ...
+# unlimit _smp_mflags in system macro
+%global _smp_ncpus_max 0
+CEPH_PARALLEL_BUILD="%{?_smp_mflags}"
 %if %{with lowmem_builder}
-%if 0%{?jobs} > 8
-%define _smp_mflags -j8
-%endif
+lo_jobs="%{?jobs:%{jobs}}"
+%if 0%{?suse_version}
+%ifarch %arm
+    %if ! 0%{?qemu_user_space_build:1}
+        # native hardware is not that powerful
+        lo_jobs="1"
+    %endif
+%endif
+%endif
+# do not eat all memory
+echo "Available memory:"
+free
+echo "System limits:"
+ulimit -a
+lo_jobs_reduced=
+if test -n "$lo_jobs" -a "$lo_jobs" -gt 1 ; then
+    mem_per_process=1600
+    max_mem=$(LANG=C free -t -m | sed -n "s|^Mem: *\([0-9]*\).*$|\1|p")
+    max_jobs="$(($max_mem / $mem_per_process))"
+    test "$lo_jobs" -gt "$max_jobs" && lo_jobs="$max_jobs" && lo_jobs_reduced="yes" && echo "Warning: Reducing build parallelism to -j$max_jobs because of memory limits"
+    test "$lo_jobs" -le 0 && lo_jobs=1 && echo "Warning: Not using parallel build at all because of memory limits"
+fi
+# run make
+if test -n "$lo_jobs" ; then
+  CEPH_PARALLEL_BUILD="-j$lo_jobs"
+fi
 %endif
-
-# unlimit _smp_mflags in system macro if not set above
-%define _smp_ncpus_max 0
-# extract the number of processors for use with cmake
-%define _smp_ncpus %(echo %{_smp_mflags} | sed 's/-j//')
+export CEPH_PARALLEL_BUILD
+export CEPH_SMP_NCPUS=$(echo "$CEPH_PARALLEL_BUILD" | sed 's/-j//')
+
+env | sort
 
 mkdir build
 cd build
@@ -853,9 +880,9 @@ cmake .. \
 %else
     -DWITH_RADOSGW_BEAST_FRONTEND=OFF \
 %endif
-    -DBOOST_J=%{_smp_ncpus}
+    -DBOOST_J=$CEPH_SMP_NCPUS
 
-make %{?_smp_mflags}
+make "$CEPH_PARALLEL_BUILD"
 
 
 %if 0%{with make_check}