diff --git a/src/main/java/com/google/devtools/build/lib/BUILD b/src/main/java/com/google/devtools/build/lib/BUILD
index 55939a1..6949316 100644
--- a/src/main/java/com/google/devtools/build/lib/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/BUILD
@@ -488,6 +488,7 @@
         ":skylarkinterface",
         ":util",
         "//src/main/java/com/google/devtools/build/lib/cmdline",
+        "//src/main/java/com/google/devtools/build/lib/collect/compacthashset",
         "//src/main/java/com/google/devtools/build/lib/collect/nestedset",
         "//src/main/java/com/google/devtools/build/lib/concurrent",
         "//src/main/java/com/google/devtools/build/lib/profiler",
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
index c0ae74e..6875247 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
@@ -22,8 +22,10 @@
 import com.google.common.cache.LoadingCache;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.collect.compacthashset.CompactHashSet;
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkInterfaceUtils;
@@ -39,7 +41,6 @@
 import java.util.Comparator;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
-import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -498,15 +499,16 @@
         "struct field methods should be handled by DotExpression separately");
 
     ImmutableList<ParamDescriptor> parameters = method.getParameters();
-    ImmutableList.Builder<Object> builder =
-        ImmutableList.builderWithExpectedSize(parameters.size() + EXTRA_ARGS_COUNT);
+    List<Object> builder = new ArrayList<>(parameters.size() + EXTRA_ARGS_COUNT);
     boolean acceptsExtraArgs = method.isAcceptsExtraArgs();
     boolean acceptsExtraKwargs = method.isAcceptsExtraKwargs();
 
     int argIndex = 0;
 
     // Process parameters specified in callable.parameters()
-    Set<String> keys = new LinkedHashSet<>(kwargs.keySet());
+    // Many methods don't have any kwargs, so don't allocate a new hash set in that case.
+    Set<String> keys =
+        kwargs.isEmpty() ? ImmutableSet.of() : CompactHashSet.create(kwargs.keySet());
     // Positional parameters are always enumerated before non-positional parameters,
     // And default-valued positional parameters are always enumerated after other positional
     // parameters. These invariants are validated by the SkylarkCallable annotation processor.
@@ -541,7 +543,7 @@
         }
         argIndex++;
       } else { // No more positional arguments, or no more positional parameters.
-        if (param.isNamed() && keys.remove(param.getName())) {
+        if (param.isNamed() && !keys.isEmpty() && keys.remove(param.getName())) {
           // Param specified by keyword argument.
           value = kwargs.get(param.getName());
           if (!type.contains(value)) {
@@ -607,7 +609,7 @@
     }
     appendExtraInterpreterArgs(builder, method, this, getLocation(), environment);
 
-    return builder.build().toArray();
+    return builder.toArray();
   }
 
   private EvalException unspecifiedParameterException(
@@ -701,9 +703,9 @@
    */
   public static List<Object> extraInterpreterArgs(
       MethodDescriptor method, @Nullable FuncallExpression ast, Location loc, Environment env) {
-    ImmutableList.Builder<Object> builder = ImmutableList.builder();
+    List<Object> builder = new ArrayList<>();
     appendExtraInterpreterArgs(builder, method, ast, loc, env);
-    return builder.build();
+    return ImmutableList.copyOf(builder);
   }
 
   /**
@@ -714,7 +716,7 @@
    * @see #extraInterpreterArgs(MethodDescriptor, FuncallExpression, Location, Environment)
    */
   private static void appendExtraInterpreterArgs(
-      ImmutableList.Builder<Object> builder,
+      List<Object> builder,
       MethodDescriptor method,
       @Nullable FuncallExpression ast,
       Location loc,