[GitHub] [kafka] hachikuji commented on a diff in pull request #12625: KAFKA-14222; KRaft's memory pool should always allocate a buffer

[GitBox <gi...@apache.org>]

hachikuji commented on code in PR #12625:
URL: https://github.com/apache/kafka/pull/12625#discussion_r968988957


##########
raft/src/test/java/org/apache/kafka/raft/internals/BatchMemoryPoolTest.java:
##########
@@ -104,4 +128,15 @@ public void testReleaseBufferNotMatchingBatchSize() {
         assertThrows(IllegalArgumentException.class, () -> pool.release(buffer));
     }
 
+    private ByteBuffer touch(ByteBuffer buffer) {

Review Comment:
   nit: `touch` seems a little vague. I think we're just trying to simulate some buffer usage?



##########
raft/src/main/java/org/apache/kafka/raft/internals/BatchMemoryPool.java:
##########
@@ -72,7 +74,13 @@ public void release(ByteBuffer previouslyAllocated) {
                     + previouslyAllocated.limit());
             }
 
-            free.offer(previouslyAllocated);
+            // Free the buffer if the number of pooled buffers is already the maximum number of batches.
+            // Otherwise return the buffer to the memory pool.
+            if (free.size() >= maxBatches) {

Review Comment:
   Perhaps we should rename `maxBatches` since it is no longer serving as a max. How about `maxRetainedBatches` or something like that since it is still a bound on the number of batches which the pool can hold onto indefinitely.



##########
raft/src/main/java/org/apache/kafka/raft/internals/BatchMemoryPool.java:
##########
@@ -90,18 +98,12 @@ public long size() {
 
     @Override
     public long availableMemory() {
-        lock.lock();
-        try {
-            int freeBatches = free.size() + (maxBatches - numAllocatedBatches);
-            return freeBatches * (long) batchSize;
-        } finally {
-            lock.unlock();
-        }
+        return Integer.MAX_VALUE;

Review Comment:
   2 billion bytes is 2GB? Is that enough?



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