uschindler commented on a change in pull request #1397: LUCENE-9304: Refactor
DWPTPool to pool DWPT directly
URL: https://github.com/apache/lucene-solr/pull/1397#discussion_r404610773
##########
File path:
lucene/core/src/java/org/apache/lucene/index/DocumentsWriterPerThreadPool.java
##########
@@ -16,228 +16,173 @@
*/
package org.apache.lucene.index;
+import java.io.Closeable;
+import java.io.IOException;
import java.util.ArrayList;
+import java.util.Collections;
+import java.util.IdentityHashMap;
+import java.util.Iterator;
import java.util.List;
-import java.util.concurrent.locks.ReentrantLock;
+import java.util.Set;
+import java.util.function.Predicate;
+import org.apache.lucene.store.AlreadyClosedException;
+import org.apache.lucene.util.IOSupplier;
import org.apache.lucene.util.ThreadInterruptedException;
/**
- * {@link DocumentsWriterPerThreadPool} controls {@link ThreadState} instances
- * and their thread assignments during indexing. Each {@link ThreadState} holds
- * a reference to a {@link DocumentsWriterPerThread} that is once a
- * {@link ThreadState} is obtained from the pool exclusively used for indexing
a
- * single document by the obtaining thread. Each indexing thread must obtain
- * such a {@link ThreadState} to make progress. Depending on the
- * {@link DocumentsWriterPerThreadPool} implementation {@link ThreadState}
+ * {@link DocumentsWriterPerThreadPool} controls {@link
DocumentsWriterPerThread} instances
+ * and their thread assignments during indexing. Each {@link
DocumentsWriterPerThread} is once a
+ * obtained from the pool exclusively used for indexing a
+ * single document or list of documents by the obtaining thread. Each indexing
thread must obtain
+ * such a {@link DocumentsWriterPerThread} to make progress. Depending on the
+ * {@link DocumentsWriterPerThreadPool} implementation {@link
DocumentsWriterPerThread}
* assignments might differ from document to document.
* <p>
- * Once a {@link DocumentsWriterPerThread} is selected for flush the thread
pool
- * is reusing the flushing {@link DocumentsWriterPerThread}s ThreadState with a
- * new {@link DocumentsWriterPerThread} instance.
+ * Once a {@link DocumentsWriterPerThread} is selected for flush the {@link
DocumentsWriterPerThread} will
+ * be checked out of the thread pool and won't be reused for indexing. See
{@link #checkout(DocumentsWriterPerThread)}.
* </p>
*/
-final class DocumentsWriterPerThreadPool {
-
- /**
- * {@link ThreadState} references and guards a
- * {@link DocumentsWriterPerThread} instance that is used during indexing to
- * build a in-memory index segment. {@link ThreadState} also holds all flush
- * related per-thread data controlled by {@link DocumentsWriterFlushControl}.
- * <p>
- * A {@link ThreadState}, its methods and members should only accessed by one
- * thread a time. Users must acquire the lock via {@link ThreadState#lock()}
- * and release the lock in a finally block via {@link ThreadState#unlock()}
- * before accessing the state.
- */
- @SuppressWarnings("serial")
- final static class ThreadState extends ReentrantLock {
- DocumentsWriterPerThread dwpt;
- // TODO this should really be part of DocumentsWriterFlushControl
- // write access guarded by DocumentsWriterFlushControl
- volatile boolean flushPending = false;
- // TODO this should really be part of DocumentsWriterFlushControl
- // write access guarded by DocumentsWriterFlushControl
- long bytesUsed = 0;
-
- // set by DocumentsWriter after each indexing op finishes
- volatile long lastSeqNo;
-
- ThreadState(DocumentsWriterPerThread dpwt) {
- this.dwpt = dpwt;
- }
-
- private void reset() {
- assert this.isHeldByCurrentThread();
- this.dwpt = null;
- this.bytesUsed = 0;
- this.flushPending = false;
- }
-
- boolean isInitialized() {
- assert this.isHeldByCurrentThread();
- return dwpt != null;
- }
-
- /**
- * Returns the number of currently active bytes in this ThreadState's
- * {@link DocumentsWriterPerThread}
- */
- public long getBytesUsedPerThread() {
- assert this.isHeldByCurrentThread();
- // public for FlushPolicy
- return bytesUsed;
- }
-
- /**
- * Returns this {@link ThreadState}s {@link DocumentsWriterPerThread}
- */
- public DocumentsWriterPerThread getDocumentsWriterPerThread() {
- assert this.isHeldByCurrentThread();
- // public for FlushPolicy
- return dwpt;
- }
-
- /**
- * Returns <code>true</code> iff this {@link ThreadState} is marked as
flush
- * pending otherwise <code>false</code>
- */
- public boolean isFlushPending() {
- return flushPending;
- }
- }
+final class DocumentsWriterPerThreadPool implements
Iterable<DocumentsWriterPerThread>, Closeable {
- private final List<ThreadState> threadStates = new ArrayList<>();
+ private final Set<DocumentsWriterPerThread> dwpts =
Collections.newSetFromMap(new IdentityHashMap<>());
+ private final List<DocumentsWriterPerThread> freeList = new ArrayList<>();
Review comment:
Just an idea: Maybe use `Deque<DocumentsWriterPerThread> freeList = new
ArrayDeque<>();` here, as it allows to iterate in borth directions (it has
`descendingIterator()`). To me this also looks better, because the whole thing
is mostly used as a deque (LIFO).
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