private int allocateFromDiscardResult(MemoryBuffer[] dest, int destAllocIx,
      int freeListIx, int allocationSize, DiscardContext discardResult) {
    for (int i = 0; i < discardResult.resultCount; ++i) {
      long result = discardResult.results[i];
      destAllocIx = arenas[getFirstInt(result)].allocateFromDiscard(
          dest, destAllocIx, getSecondInt(result), freeListIx, allocationSize);
    }
    return destAllocIx;
  }
Tries to allocate destCount - destIx blocks after the forced eviction of some other buffers.
Args the same as allocateFast.
llap-server/src/java/org/apache/hadoop/hive/llap/cache/BuddyAllocator.java