Use all cores for jtreg instead of halving (adoptium#4933)

Signed-off-by: Stewart X Addison <[email protected]>

openjdk/openjdk.mk

@@ -19,7 +19,7 @@ OS:=$(shell uname -s)
 
 ifeq ($(OS),Linux)
 	NPROCS:=$(shell grep -c ^processor /proc/cpuinfo)
-	MEMORY_SIZE:=$(shell KMEMMB=`awk '/^MemTotal:/{print int($$2/1024)}' /proc/meminfo`; if [ -r /sys/fs/cgroup/memory/memory.limit_in_bytes ]; then CGMEM=`cat /sys/fs/cgroup/memory/memory.limit_in_bytes`; else CGMEM=`expr $${KMEMMB} \* 1024`; fi; CGMEMMB=`expr $${CGMEM} / 1048576`; if [ "$${KMEMMB}" -lt "$${CGMEMMB}" ]; then echo "$${KMEMMB}"; else echo "$${CGMEMMB}"; fi)
+	MEMORY_SIZE:=$(shell KMEMMB=`awk '/^MemTotal:/{print int($$2/1024)}' /proc/meminfo`; if [ -r /sys/fs/cgroup/memory/memory.limit_in_bytes ]; then CGMEM=`cat /sys/fs/cgroup/memory/memory.limit_in_bytes`; else CGMEM=`expr $${KMEMMB} \* 1024`; fi; CGMEMMB=`expr $${CGMEM} / 1024`; if [ "$${KMEMMB}" -lt "$${CGMEMMB}" ]; then echo "$${KMEMMB}"; else echo "$${CGMEMMB}"; fi)
 endif
 ifeq ($(OS),Darwin)
 	NPROCS:=$(shell sysctl -n hw.ncpu)
@@ -46,7 +46,7 @@ endif
 # Upstream OpenJDK, roughly, sets concurrency based on the
 # following: min(NPROCS/2, MEM_IN_GB/2).
 MEM := $(shell expr $(MEMORY_SIZE) / 2048)
-CORE := $(shell expr $(NPROCS) / 2)
+CORE := $(shell expr $(NPROCS) / 2 + 1)
 CONC := $(CORE)
 ifeq ($(shell expr $(CORE) \> $(MEM)), 1)
 	CONC := $(MEM)