Adjust JVM heap size for extremely large memory machine

sdks/go.mod

@@ -20,7 +20,7 @@
 // directory.
 module github.com/apache/beam/sdks/v2
 
-go 1.20
+go 1.21
 
 require (
 	cloud.google.com/go/bigquery v1.60.0

sdks/java/container/boot.go

@@ -248,18 +248,18 @@ func main() {
 }
 
 // heapSizeLimit returns 80% of the runner limit, if provided. If not provided,
-// it returns 70% of the physical memory on the machine. If it cannot determine
-// that value, it returns 1GB. This is an imperfect heuristic. It aims to
-// ensure there is memory for non-heap use and other overhead, while also not
-// underutilizing the machine. if set_recommended_max_xmx experiment is enabled,
-// sets xmx to 32G. Under 32G JVM enables CompressedOops. CompressedOops
-// utilizes memory more efficiently, and has positive impact on GC performance
-// and cache hit rate.
+// it returns max(70% M, M - 32GB) where M the physical memory on the machine.
+// If it cannot determine that value, it returns 1GB. This is an imperfect
+// heuristic. It aims to ensure there is memory for non-heap use and other
+// overhead, while also not underutilizing the machine.
+// if set_recommended_max_xmx experiment is enabled, sets xmx to 32G. Under 32G
+// JVM enables CompressedOops. CompressedOops utilizes memory more efficiently,
+// and has positive impact on GC performance and cache hit rate.
 func heapSizeLimit(info *fnpb.ProvisionInfo, setRecommendedMaxXmx bool) uint64 {
 	if setRecommendedMaxXmx {
 		return 32 << 30
 	} else if size, err := syscallx.PhysicalMemorySize(); err == nil {
-		return (size * 70) / 100
+		return max(size - (32 << 30), (size * 70) / 100)
 	}
 	return 1 << 30
 }