[HIVE-21686] ensure that memory allocator does not evict using brute …

common/src/java/org/apache/hadoop/hive/conf/HiveConf.java

@@ -4053,6 +4053,10 @@ public static enum ConfVars {
     LLAP_ALLOCATOR_DEFRAG_HEADROOM("hive.llap.io.allocator.defrag.headroom", "1Mb",
         "How much of a headroom to leave to allow allocator more flexibility to defragment.\n" +
         "The allocator would further cap it to a fraction of total memory."),
+    LLAP_ALLOCATOR_MAX_FORCE_EVICTED("hive.llap.io.allocator.max.force.eviction", "16Mb",
+        "Fragmentation can lead to some cases where more eviction has to happen to accommodate allocations\n" +
+            " This configuration puts a limit on how many bytes to force evict before using Allocator Discard method."
+            + " Higher values will allow allocator more flexibility and will lead to better caching."),
     LLAP_TRACK_CACHE_USAGE("hive.llap.io.track.cache.usage", true,
          "Whether to tag LLAP cache contents, mapping them to Hive entities (paths for\n" +
          "partitions and tables) for reporting."),

llap-server/src/java/org/apache/hadoop/hive/llap/cache/BuddyAllocatorMXBean.java

@@ -22,41 +22,41 @@
 /**
  * MXbean to expose cache allocator related information through JMX.
  */
-@MXBean
-public interface BuddyAllocatorMXBean {
+@MXBean public interface BuddyAllocatorMXBean {
 
   /**
    * Gets if bytebuffers are allocated directly offheap.
    *
    * @return gets if direct bytebuffer allocation
    */
-  public boolean getIsDirect();
+  boolean getIsDirect();
 
   /**
    * Gets minimum allocation size of allocator.
    *
    * @return minimum allocation size
    */
-  public int getMinAllocation();
+  int getMinAllocation();
 
   /**
    * Gets maximum allocation size of allocator.
    *
    * @return maximum allocation size
    */
-  public int getMaxAllocation();
+  int getMaxAllocation();
 
   /**
    * Gets the arena size.
    *
    * @return arena size
    */
-  public int getArenaSize();
+  int getArenaSize();
 
   /**
    * Gets the maximum cache size.
    *
    * @return max cache size
    */
-  public long getMaxCacheSize();
-}
+  long getMaxCacheSize();
+
+}

llap-server/src/java/org/apache/hadoop/hive/llap/cache/LowLevelCacheMemoryManager.java

@@ -66,6 +66,15 @@ public void reserveMemory(final long memoryToReserve, AtomicBoolean isStopped) {
     throw new ReserveFailedException(isStopped);
   }
 
+  @Override public long evictMemory(long memoryToEvict) {
+    if (evictor == null) {
+      return 0;
+    }
+    long evicted = evictor.evictSomeBlocks(memoryToEvict);
+    releaseMemory(evicted);
+    return evicted;
+  }
+
   @VisibleForTesting
   public boolean reserveMemory(final long memoryToReserve,
       boolean waitForEviction, AtomicBoolean isStopped) {
@@ -154,4 +163,9 @@ public long purge() {
     metrics.incrCacheCapacityUsed(-evicted);
     return evicted;
   }
+
+  @VisibleForTesting
+  public long getCurrentUsedSize() {
+    return usedMemory.get();
+  }
 }

llap-server/src/java/org/apache/hadoop/hive/llap/cache/MemoryManager.java

@@ -57,4 +57,13 @@ public interface MemoryManager {
    *                        allocate the space.
    */
   void reserveMemory(long memoryToReserve, AtomicBoolean isStopped);
+
+  /**
+   * Request the memory manager to evict more memory, this will be blocking and might return 0 if nothing was evicted.
+   *
+   * @param memoryToEvict amount of bytes to evict.
+   * @return actual amount of evicted bytes.
+   */
+  long evictMemory(long memoryToEvict);
+
 }

llap-server/src/test/org/apache/hadoop/hive/llap/cache/TestBuddyAllocator.java

@@ -62,6 +62,10 @@ static class DummyMemoryManager implements MemoryManager {
     public void reserveMemory(long memoryToReserve, AtomicBoolean isStopped) {
     }
 
+    @Override public long evictMemory(long memoryToEvict) {
+      return 0;
+    }
+
     @Override
     public void releaseMemory(long memUsage) {
     }
@@ -93,8 +97,7 @@ public void testSameSizes() throws Exception {
     }
   }
 
-  @Test
-  public void testMultipleArenas() throws Exception {
+  @Test public void testMultipleArenas() throws Exception {
     int max = 8, maxAlloc = 1 << max, allocLog2 = max - 1, arenaCount = 5;
     BuddyAllocator a = new BuddyAllocator(isDirect, isMapped, 1 << 3, maxAlloc, maxAlloc,
         maxAlloc * arenaCount, 0, tmpDir, new DummyMemoryManager(),