diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/log/jul/BaseJulLogger.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/log/jul/BaseJulLogger.java
index e8a1fe6f..0490efd2 100644
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/log/jul/BaseJulLogger.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/log/jul/BaseJulLogger.java
@@ -90,7 +90,9 @@ public class BaseJulLogger {
         if (handler != null) {
             disableOtherHandlers(heliumRecordLog, handler);
         }
-        heliumRecordLog.setLevel(Level.ALL);
+
+        // Set log level to INFO by default
+        heliumRecordLog.setLevel(Level.INFO);
         return handler;
     }
 
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/DefaultSlotChainBuilder.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/DefaultSlotChainBuilder.java
index 797206bb..cf0f72c5 100755
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/DefaultSlotChainBuilder.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/DefaultSlotChainBuilder.java
@@ -38,7 +38,7 @@ public class DefaultSlotChainBuilder implements SlotChainBuilder {
         ProcessorSlotChain chain = new DefaultProcessorSlotChain();
 
         // Note: the instances of ProcessorSlot should be different, since they are not stateless.
-        List<ProcessorSlot> sortedSlotList = SpiLoader.loadDifferentInstanceListSorted(ProcessorSlot.class);
+        List<ProcessorSlot> sortedSlotList = SpiLoader.loadPrototypeInstanceListSorted(ProcessorSlot.class);
         for (ProcessorSlot slot : sortedSlotList) {
             if (!(slot instanceof AbstractLinkedProcessorSlot)) {
                 RecordLog.warn("The ProcessorSlot(" + slot.getClass().getCanonicalName() + ") is not an instance of AbstractLinkedProcessorSlot, can't be added into ProcessorSlotChain");
diff --git a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/SpiLoader.java b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/SpiLoader.java
index a677084e..47b3342a 100644
--- a/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/SpiLoader.java
+++ b/sentinel-core/src/main/java/com/alibaba/csp/sentinel/util/SpiLoader.java
@@ -34,6 +34,14 @@ public final class SpiLoader {
 
     private static final Map<String, ServiceLoader> SERVICE_LOADER_MAP = new ConcurrentHashMap<String, ServiceLoader>();
 
+    /**
+     * Load the first-found specific SPI instance
+     *
+     * @param clazz class of the SPI interface
+     * @param <T>   SPI type
+     * @return the first specific SPI instance if exists, or else return null
+     * @since 1.7.0
+     */
     public static <T> T loadFirstInstance(Class<T> clazz) {
         AssertUtil.notNull(clazz, "SPI class cannot be null");
         try {
@@ -52,7 +60,7 @@ public final class SpiLoader {
                 return null;
             }
         } catch (Throwable t) {
-            RecordLog.warn("[SpiLoader] ERROR: loadFirstInstance failed", t);
+            RecordLog.error("[SpiLoader] ERROR: loadFirstInstance failed", t);
             t.printStackTrace();
             return null;
         }
@@ -87,7 +95,7 @@ public final class SpiLoader {
             }
             return defaultClass.newInstance();
         } catch (Throwable t) {
-            RecordLog.warn("[SpiLoader] ERROR: loadFirstInstanceOrDefault failed", t);
+            RecordLog.error("[SpiLoader] ERROR: loadFirstInstanceOrDefault failed", t);
             t.printStackTrace();
             return null;
         }
@@ -96,6 +104,8 @@ public final class SpiLoader {
     /**
      * Load the SPI instance with highest priority.
      *
+     * Note: each call return same instances.
+     *
      * @param clazz class of the SPI
      * @param <T>   SPI type
      * @return the SPI instance with highest priority if exists, or else false
@@ -114,15 +124,15 @@ public final class SpiLoader {
             SpiOrderWrapper<T> w = null;
             for (T spi : serviceLoader) {
                 int order = SpiOrderResolver.resolveOrder(spi);
-                RecordLog.info("[SpiLoader] Found {} SPI: {} with order " + order, clazz.getSimpleName(),
-                    spi.getClass().getCanonicalName());
+                RecordLog.info("[SpiLoader] Found {} SPI: {} with order {}", clazz.getSimpleName(),
+                    spi.getClass().getCanonicalName(), order);
                 if (w == null || order < w.order) {
                     w = new SpiOrderWrapper<>(order, spi);
                 }
             }
             return w == null ? null : w.spi;
         } catch (Throwable t) {
-            RecordLog.warn("[SpiLoader] ERROR: loadHighestPriorityInstance failed", t);
+            RecordLog.error("[SpiLoader] ERROR: loadHighestPriorityInstance failed", t);
             t.printStackTrace();
             return null;
         }
@@ -132,6 +142,8 @@ public final class SpiLoader {
      * Load and sorted SPI instance list.
      * Load the SPI instance list for provided SPI interface.
      *
+     * Note: each call return same instances.
+     *
      * @param clazz class of the SPI
      * @param <T>   SPI type
      * @return sorted SPI instance list
@@ -149,11 +161,13 @@ public final class SpiLoader {
 
             List<T> list = new ArrayList<>();
             for (T spi : serviceLoader) {
+                RecordLog.info("[SpiLoader] Found {} SPI: {}", clazz.getSimpleName(),
+                        spi.getClass().getCanonicalName());
                 list.add(spi);
             }
             return list;
         } catch (Throwable t) {
-            RecordLog.warn("[SpiLoader] ERROR: loadInstanceListSorted failed", t);
+            RecordLog.error("[SpiLoader] ERROR: loadInstanceList failed", t);
             t.printStackTrace();
             return new ArrayList<>();
         }
@@ -162,7 +176,7 @@ public final class SpiLoader {
     /**
      * Load the sorted SPI instance list for provided SPI interface.
      *
-     * Note: each call return new instances.
+     * Note: each call return same instances.
      *
      * @param clazz class of the SPI
      * @param <T>   SPI type
@@ -184,32 +198,32 @@ public final class SpiLoader {
                 int order = SpiOrderResolver.resolveOrder(spi);
                 // Since SPI is lazy initialized in ServiceLoader, we use online sort algorithm here.
                 SpiOrderResolver.insertSorted(orderWrappers, spi, order);
-                RecordLog.info("[SpiLoader] Found {} SPI: {} with order " + order, clazz.getSimpleName(),
-                    spi.getClass().getCanonicalName());
+                RecordLog.info("[SpiLoader] Found {} SPI: {} with order {}", clazz.getSimpleName(),
+                    spi.getClass().getCanonicalName(), order);
             }
-            List<T> list = new ArrayList<>();
+            List<T> list = new ArrayList<>(orderWrappers.size());
             for (int i = 0; i < orderWrappers.size(); i++) {
-                list.add(i, orderWrappers.get(i).spi);
+                list.add(orderWrappers.get(i).spi);
             }
             return list;
         } catch (Throwable t) {
-            RecordLog.warn("[SpiLoader] ERROR: loadInstanceListSorted failed", t);
+            RecordLog.error("[SpiLoader] ERROR: loadInstanceListSorted failed", t);
             t.printStackTrace();
             return new ArrayList<>();
         }
     }
 
     /**
-     * Load the sorted and different SPI instance list for provided SPI interface.
+     * Load the sorted and prototype SPI instance list for provided SPI interface.
      *
-     * Note: each call return new instances.
+     * Note: each call return different instances, i.e. prototype instance, not singleton instance.
      *
      * @param clazz class of the SPI
      * @param <T>   SPI type
      * @return sorted and different SPI instance list
      * @since 1.7.2
      */
-    public static <T> List<T> loadDifferentInstanceListSorted(Class<T> clazz) {
+    public static <T> List<T> loadPrototypeInstanceListSorted(Class<T> clazz) {
         try {
             // Not use SERVICE_LOADER_MAP, to make sure the instances loaded are different.
             ServiceLoader<T> serviceLoader = ServiceLoaderUtil.getServiceLoader(clazz);
@@ -219,16 +233,16 @@ public final class SpiLoader {
                 int order = SpiOrderResolver.resolveOrder(spi);
                 // Since SPI is lazy initialized in ServiceLoader, we use online sort algorithm here.
                 SpiOrderResolver.insertSorted(orderWrappers, spi, order);
-                RecordLog.info("[SpiLoader] Found {0} SPI: {1} with order " + order, clazz.getSimpleName(),
-                        spi.getClass().getCanonicalName());
+                RecordLog.debug("[SpiLoader] Found {} SPI: {} with order {}", clazz.getSimpleName(),
+                        spi.getClass().getCanonicalName(), order);
             }
-            List<T> list = new ArrayList<>();
+            List<T> list = new ArrayList<>(orderWrappers.size());
             for (int i = 0; i < orderWrappers.size(); i++) {
-                list.add(i, orderWrappers.get(i).spi);
+                list.add(orderWrappers.get(i).spi);
             }
             return list;
         } catch (Throwable t) {
-            RecordLog.warn("[SpiLoader] ERROR: loadDifferentInstanceListSorted failed", t);
+            RecordLog.error("[SpiLoader] ERROR: loadPrototypeInstanceListSorted failed", t);
             t.printStackTrace();
             return new ArrayList<>();
         }
diff --git a/sentinel-core/src/test/java/com/alibaba/csp/sentinel/util/SpiLoaderTest.java b/sentinel-core/src/test/java/com/alibaba/csp/sentinel/util/SpiLoaderTest.java
index ba353fa2..622f7fd2 100644
--- a/sentinel-core/src/test/java/com/alibaba/csp/sentinel/util/SpiLoaderTest.java
+++ b/sentinel-core/src/test/java/com/alibaba/csp/sentinel/util/SpiLoaderTest.java
@@ -44,9 +44,17 @@ public class SpiLoaderTest {
         ProcessorSlot processorSlot = SpiLoader.loadFirstInstance(ProcessorSlot.class);
         assertNotNull(processorSlot);
 
+        ProcessorSlot processorSlot2 = SpiLoader.loadFirstInstance(ProcessorSlot.class);
+        // As SERVICE_LOADER_MAP in SpiLoader cached the instance, so they're same instances
+        assertSame(processorSlot, processorSlot2);
+
         SlotChainBuilder slotChainBuilder = SpiLoader.loadFirstInstance(SlotChainBuilder.class);
         assertNotNull(slotChainBuilder);
         assertTrue(slotChainBuilder instanceof DefaultSlotChainBuilder);
+
+        SlotChainBuilder slotChainBuilder2 = SpiLoader.loadFirstInstance(SlotChainBuilder.class);
+        // As SERVICE_LOADER_MAP in SpiLoader cached the instance, so they're same instances
+        assertSame(slotChainBuilder, slotChainBuilder2);
     }
 
     @Test
@@ -54,8 +62,12 @@ public class SpiLoaderTest {
         ProcessorSlot processorSlot = SpiLoader.loadHighestPriorityInstance(ProcessorSlot.class);
         assertNotNull(processorSlot);
 
-        // NodeSelectorSlot is highest order with @SpiOrder(-9000), among all slots
+        // NodeSelectorSlot is highest order with @SpiOrder(-10000), among all slots
         assertTrue(processorSlot instanceof NodeSelectorSlot);
+
+        ProcessorSlot processorSlot2 = SpiLoader.loadHighestPriorityInstance(ProcessorSlot.class);
+        // As SERVICE_LOADER_MAP in SpiLoader cached the instance, so they're same instances
+        assertSame(processorSlot, processorSlot2);
     }
 
     @Test
@@ -66,14 +78,15 @@ public class SpiLoaderTest {
         // Total 8 default slot in sentinel-core
         assertEquals(8, slots.size());
 
-        // Store the first slot of slots
+        // Get the first slot of slots
         ProcessorSlot firstSlot = slots.get(0);
 
         // Call loadInstanceList again
         List<ProcessorSlot> slots2 = SpiLoader.loadInstanceList(ProcessorSlot.class);
+        // Note: the return list are different, and the item instances in list are same
         assertNotSame(slots, slots2);
 
-        // Store the first slot of slots
+        // Get the first slot of slots2
         ProcessorSlot firstSlot2 = slots2.get(0);
 
         // As SERVICE_LOADER_MAP in SpiLoader cached the instance, so they're same instances
@@ -100,6 +113,7 @@ public class SpiLoaderTest {
         assertTrue(sortedSlots.get(index++) instanceof DegradeSlot);
 
         // Verify each call return different instances
+        // Note: the return list are different, and the item instances in list are same
         List<ProcessorSlot> sortedSlots2 = SpiLoader.loadInstanceListSorted(ProcessorSlot.class);
         assertNotSame(sortedSlots, sortedSlots2);
         assertEquals(sortedSlots.size(), sortedSlots2.size());
@@ -107,11 +121,14 @@ public class SpiLoaderTest {
             ProcessorSlot slot = sortedSlots.get(i);
             ProcessorSlot slot2 = sortedSlots2.get(i);
             assertEquals(slot.getClass(), slot2.getClass());
+
+            // As SERVICE_LOADER_MAP in SpiLoader cached the instance, so they're same instances
+            assertSame(slot, slot2);
         }
     }
 
     @Test
-    public void testLoadDifferentInstanceListSorted() {
+    public void testLoadPrototypeInstanceListSorted() {
         List<ProcessorSlot> sortedSlots = SpiLoader.loadInstanceListSorted(ProcessorSlot.class);
         assertNotNull(sortedSlots);
 
@@ -129,8 +146,8 @@ public class SpiLoaderTest {
         assertTrue(sortedSlots.get(index++) instanceof FlowSlot);
         assertTrue(sortedSlots.get(index++) instanceof DegradeSlot);
 
-        // Verify each call return different instances
-        List<ProcessorSlot> sortedSlots2 = SpiLoader.loadDifferentInstanceListSorted(ProcessorSlot.class);
+        // Verify each call return new instances
+        List<ProcessorSlot> sortedSlots2 = SpiLoader.loadPrototypeInstanceListSorted(ProcessorSlot.class);
         assertNotSame(sortedSlots, sortedSlots2);
         assertEquals(sortedSlots.size(), sortedSlots2.size());
         for (int i = 0; i < sortedSlots.size(); i++) {