[GitHub] [bookkeeper] hangc0276 commented on a change in pull request #2932: direct-io: add support for bypassing operating system I/O cache when logging entries

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

hangc0276 commented on a change in pull request #2932:
URL: https://github.com/apache/bookkeeper/pull/2932#discussion_r771386466



##########
File path: bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/storage/ldb/DbLedgerStorage.java
##########
@@ -77,6 +83,18 @@
     public static final String WRITE_CACHE_MAX_SIZE_MB = "dbStorage_writeCacheMaxSizeMb";
 
     public static final String READ_AHEAD_CACHE_MAX_SIZE_MB = "dbStorage_readAheadCacheMaxSizeMb";
+    static final String READ_AHEAD_CACHE_BATCH_SIZE = "dbStorage_readAheadCacheBatchSize";
+    public static final String DIRECT_IO_ENTRYLOGGER = "dbStorage_directIOEntryLogger";
+    public static final String DIRECT_IO_ENTRYLOGGER_TOTAL_WRITEBUFFER_SIZE_MB =
+            "dbStorage_directIOEntryLoggerTotalWriteBufferSizeMb";
+    public static final String DIRECT_IO_ENTRYLOGGER_TOTAL_READBUFFER_SIZE_MB =
+            "dbStorage_directIOEntryLoggerReadBufferSizeMb";

Review comment:
       dbStorage_directIOEntryLoggerTotalReadBufferSizeMb ?

##########
File path: bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/storage/directentrylogger/WriterWithMetadata.java
##########
@@ -0,0 +1,79 @@
+/**
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+package org.apache.bookkeeper.bookie.storage.directentrylogger;
+
+import static com.google.common.base.Preconditions.checkState;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufAllocator;
+import java.io.IOException;
+import org.apache.bookkeeper.bookie.EntryLogMetadata;
+
+/**
+ * WriterWithMetadata.
+ */
+class WriterWithMetadata {
+    private final LogWriter writer;
+    private final EntryLogMetadata metadata;
+    private final ByteBufAllocator allocator;
+
+    WriterWithMetadata(LogWriter writer, EntryLogMetadata metadata,
+                       ByteBufAllocator allocator) throws IOException {
+        this.writer = writer;
+        this.metadata = metadata;
+        this.allocator = allocator;
+
+        ByteBuf buf = allocator.buffer(Buffer.ALIGNMENT);
+        try {

Review comment:
       Does the writer write EmptyHeader twice? the emptyHeader has been written on `newDirectWriter` creation.




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