torture: Scale scftorture memory based on number of CPUs

As the number of CPUs increases, the number of outstanding no-wait
smp_call_function() handlers also increases, so that the default of
2G of memory is not always sufficient on 80-CPU systems.  This commit
therefore scales the amount of memory specified to qemu based on the
number of CPUs specified to the scftorture test instance.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Author: paulmckrcu

tools/testing/selftests/rcutorture/bin/torture.sh

@@ -376,8 +376,10 @@ fi
 
 if test "$do_scftorture" = "yes"
 then
+	# Scale memory based on the number of CPUs.
+	scfmem=$((2+HALF_ALLOTED_CPUS/16))
 	torture_bootargs="scftorture.nthreads=$HALF_ALLOTED_CPUS torture.disable_onoff_at_boot csdlock_debug=1"
-	torture_set "scftorture" tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration "$duration_scftorture" --configs "$configs_scftorture" --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 2G --trust-make
+	torture_set "scftorture" tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration "$duration_scftorture" --configs "$configs_scftorture" --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory ${scfmem}G --trust-make
 fi
 
 if test "$do_rt" = "yes"