utils: use optimal path then creating Subject from unix principals

Motivation:

The sanity checks in Subject class are too expensive when to constructor
set of principal is passed, as internally a new LinkedList copy is created:

Benchmark                               Mode  Cnt        Score       Error  Units
SubjectBenchmark.subjectByAddingToSet  thrpt    9  2061025.436 ± 24807.881  ops/s
SubjectBenchmark.subjectByPassingSet   thrpt    9  1341492.178 ± 34701.882  ops/s

Modification:

Update UnixSubjects#toSubject to use more optimal form.
Added benchmark.

Result:
Not a real performance boost, but anyway :)

Acked-by: Karen Hoyos
Target: master

Author: kofemann

benchmarks/src/main/java/org/dcache/nfs/benchmarks/SubjectBenchmark.java

@@ -0,0 +1,54 @@
+package org.dcache.nfs.benchmarks;
+
+import com.sun.security.auth.UnixNumericGroupPrincipal;
+import com.sun.security.auth.UnixNumericUserPrincipal;
+import java.security.Principal;
+import java.util.Set;
+import javax.security.auth.Subject;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+
+@BenchmarkMode(Mode.Throughput)
+@State(Scope.Benchmark)
+public class SubjectBenchmark {
+
+
+    @Benchmark
+    public Subject subjectByAddingToSet() {
+        Subject subject = new Subject();
+        subject.getPrincipals().add(new UnixNumericUserPrincipal(0));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(0, true));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(1, false));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(2, false));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(3, false));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(4, false));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(5, false));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(6, false));
+        subject.setReadOnly();
+        return subject;
+    }
+
+
+    @Benchmark
+    public Subject subjectByPassingSet() {
+
+        Principal[] principals = new Principal[]{
+              new UnixNumericUserPrincipal(0),
+              new UnixNumericGroupPrincipal(0, true),
+              new UnixNumericGroupPrincipal(1, false),
+              new UnixNumericGroupPrincipal(2, false),
+              new UnixNumericGroupPrincipal(3, false),
+              new UnixNumericGroupPrincipal(4, false),
+              new UnixNumericGroupPrincipal(5, false),
+              new UnixNumericGroupPrincipal(6, false)
+        };
+
+        return new Subject(true, Set.of(principals), Set.of(), Set.of());
+    }
+}
+
+

core/src/main/java/org/dcache/nfs/util/UnixSubjects.java

@@ -95,10 +95,11 @@ public static boolean hasGid(Subject subject, long gid) {
      * @return subject with given uid, gid.
      */
     public static Subject toSubject(long uid, long gid) {
-        return new Subject(false,
-                Set.of(new UnixNumericUserPrincipal(uid), new UnixNumericGroupPrincipal(gid, true)),
-                Set.of(),
-                Set.of());
+        var subject = new Subject();
+        subject.getPrincipals().add(new UnixNumericUserPrincipal(uid));
+        subject.getPrincipals().add(new UnixNumericGroupPrincipal(gid, true));
+
+        return subject;
     }
 
     /**
@@ -110,12 +111,10 @@ public static Subject toSubject(long uid, long gid) {
      * @return subject with given uid, gid and gids.
      */
     public static Subject toSubject(long uid, long gid, long... gids) {
-        Subject subject = toSubject(uid, gid);
-        subject.getPrincipals()
-                .addAll(
-                        Arrays.stream(gids)
-                                .mapToObj(l -> new UnixNumericGroupPrincipal(l, false))
-                                .collect(Collectors.toSet()));
+        var subject = toSubject(uid, gid);
+        for (long aux : gids) {
+            subject.getPrincipals().add(new UnixNumericGroupPrincipal(aux, false));
+        }
         return subject;
     }