scons-utils.eclass: Use nproc when --jobs is used without an argument

Try to guess the number of processors when --jobs is passed without
an argument. We can't use a high number equivalent to GNU make behavior
(no limit) since SCons does not have an equivalent of --load-avg option.
Still, this is better than assuming some random, fixed number.

diff --git a/eclass/scons-utils.eclass b/eclass/scons-utils.eclass
index 31852820472994815987f7c2f2205e2bcbda7856..89618f93874fac949b79236cd9b1e1799507ecf4 100644 (file)
--- a/eclass/scons-utils.eclass
+++ b/eclass/scons-utils.eclass
@@ -149,6 +149,32 @@ escons() {
        return ${ret}
 }
 
+# @FUNCTION: _scons_get_default_jobs
+# @INTERNAL
+# @DESCRIPTION:
+# Output the default number of jobs, used if -j is used without
+# argument. Tries to figure out the number of logical CPUs, falling
+# back to hardcoded constant.
+_scons_get_default_jobs() {
+       local nproc
+
+       if type -P nproc &>/dev/null; then
+               # GNU
+               nproc=$(nproc)
+       elif type -P python &>/dev/null; then
+               # fallback to python2.6+
+               # note: this may fail (raise NotImplementedError)
+               nproc=$(python -c 'import multiprocessing; print(multiprocessing.cpu_count());' 2>/dev/null)
+       fi
+
+       if [[ ${nproc} ]]; then
+               echo $(( nproc + 1 ))
+       else
+               # random default
+               echo 5
+       fi
+}
+
 # @FUNCTION: _scons_clean_makeopts
 # @INTERNAL
 # @USAGE: [makeflags] [...]
@@ -192,7 +218,7 @@ _scons_clean_makeopts() {
                                        shift
                                else
                                        # no value means no limit, let's pass a random int
-                                       new_makeopts+=( ${1}=5 )
+                                       new_makeopts+=( ${1}=$(_scons_get_default_jobs) )
                                fi
                                ;;
                        # strip other long options
@@ -215,7 +241,7 @@ _scons_clean_makeopts() {
                                                                new_optstr+="j ${2}"
                                                                shift
                                                        else
-                                                               new_optstr+="j 5"
+                                                               new_optstr+="j $(_scons_get_default_jobs)"
                                                        fi
                                                        ;;
                                                # otherwise, everything after -j is treated as an arg

diff --git a/eclass/tests/scons-utils.sh b/eclass/tests/scons-utils.sh
index 6355c54517dba731d8542a318f17b024ffed42e6..fcb5125bdb1cc3340ca3dcc418cb0ba26e83cafc 100755 (executable)
--- a/eclass/tests/scons-utils.sh
+++ b/eclass/tests/scons-utils.sh
@@ -28,7 +28,7 @@ test-scons_clean_makeopts() {
 }
 
 # jobcount expected for non-specified state
-jc=5
+jc=$(_scons_get_default_jobs)
 # failed test counter
 failed=0