Simplify NCPU computation and avoid fork bombs

Summary:public
Use getconf to compute NCPU as it is uniform across platforms.

Use result in several places to avoid fork bombs.  I routinely see
errors about fork running out of memory when building e.g. the clang
plugin.

Reviewed By: jvillard

Differential Revision: D3148970

fb-gh-sync-id: 6d071c9
fbshipit-source-id: 6d071c9

Makefile.config.in

@@ -7,6 +7,8 @@
 
 PLATFORM = $(shell uname)
 
+NCPU = @NCPU@
+
 ABSOLUTE_ROOT_DIR = $(shell cd $(ROOT_DIR) && pwd)
 
 EXAMPLES_DIR = $(ABSOLUTE_ROOT_DIR)/examples

Makefile.in

@@ -29,8 +29,6 @@ TARGETS_TO_TEST += objc
 endif
 TARGETS_TO_TEST := $(shell echo $(TARGETS_TO_TEST))
 
-NCPU = @NCPU@
-
 all: $(INFER_ANALYZERS)
 
 java: inferTraceBugs

build-infer.sh

@@ -14,6 +14,7 @@ set -e
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 INFER_ROOT="$SCRIPT_DIR/../"
 PLATFORM="$(uname)"
+NCPU="$(getconf _NPROCESSORS_ONLN 2>/dev/null || echo 1)"
 
 function usage() {
   echo "Usage: $0 [-y] [targets]"
@@ -161,7 +162,7 @@ if [ "$BUILD_CLANG" = "yes" ] && ! facebook-clang-plugins/clang/setup.sh --only-
   fi
 fi
 
-make -j $TARGETS || (
+make -j $NCPU $TARGETS || (
   echo
   echo '  compilation failure; you can try running'
   echo

configure.ac

@@ -240,17 +240,11 @@ echo $buck_version > "$buckversion_file"
 AC_MSG_RESULT([$buck_version])
 
 
-AC_CHECK_TOOL([HAVE_NPROC], [nproc], [no])
-AC_CHECK_TOOL([HAVE_SYSCTL], [sysctl], [no])
+AC_CHECK_TOOL([GETCONF], [getconf], [no])
 AC_MSG_CHECKING([the number of cpus the build host has])
-if test "$HAVE_NPROC" != "no"; then
-  if test $(nproc); then
-    NCPU=$(nproc)
-    AC_MSG_RESULT([$NCPU])
-  fi
-elif test $"HAVE_SYSCTL" != "no"; then
-  if test $(sysctl -n hw.ncpu); then
-    NCPU=$(sysctl -n hw.ncpu)
+if test "$GETCONF" != "no"; then
+  if test $(getconf _NPROCESSORS_ONLN); then
+    NCPU=$(getconf _NPROCESSORS_ONLN)
     AC_MSG_RESULT([$NCPU])
   fi
 else

infer/src/Makefile.in

@@ -131,7 +131,7 @@ endif
 DEPENDENCIES = IR backend checkers eradicate harness \
 	facebook/checkers facebook/checkers/graphql facebook/scripts $(EXTRA_DEPS)
 
-OCAMLBUILD = ocamlbuild $(OCAMLBUILD_OPTIONS) -j 0 $(addprefix -I , $(DEPENDENCIES))
+OCAMLBUILD = ocamlbuild $(OCAMLBUILD_OPTIONS) -j $(NCPU) $(addprefix -I , $(DEPENDENCIES))
 
 .PHONY: all java clang llvm unit checkCopyright build_java build_clang build_llvm build_unit \
 	build_checkCopyright java_annotations clang_annotations llvm_annotations \