[Bigdata-commit] SF.net SVN: bigdata:[4281] branches/QUADS_QUERY_BRANCH/bigdata/src/java/com /bigdata

[<tho...@us...>]

Revision: 4281
          http://bigdata.svn.sourceforge.net/bigdata/?rev=4281&view=rev
Author:   thompsonbry
Date:     2011-03-08 15:12:43 +0000 (Tue, 08 Mar 2011)

Log Message:
-----------
Modified RWStrategy to explicitly pass in the offset and length of the data to be read from the RWStore. This is in preparation for examining ways of recycling the byte[] buffers in coordination with the B+Tree to reduce heap pressure.

Modified RWStore to use a double-checked locking pattern in the re-opener such that it does not always synchronize before a read or write operation on the backing channel.  This removes some sources of false contention during query.

Modified Paths:
--------------
    branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/journal/RWStrategy.java
    branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/rwstore/RWStore.java

Modified: branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/journal/RWStrategy.java
===================================================================
--- branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/journal/RWStrategy.java	2011-03-08 15:06:58 UTC (rev 4280)
+++ branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/journal/RWStrategy.java	2011-03-08 15:12:43 UTC (rev 4281)
@@ -612,7 +612,7 @@
          */
         final byte buf[] = new byte[sze + 4]; // 4 bytes for checksum
 
-        m_store.getData(rwaddr, buf);
+        m_store.getData(rwaddr, buf, 0, sze+4);
 
         return ByteBuffer.wrap(buf, 0, sze);
 

Modified: branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/rwstore/RWStore.java
===================================================================
--- branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/rwstore/RWStore.java	2011-03-08 15:06:58 UTC (rev 4280)
+++ branches/QUADS_QUERY_BRANCH/bigdata/src/java/com/bigdata/rwstore/RWStore.java	2011-03-08 15:12:43 UTC (rev 4281)
@@ -3137,35 +3137,55 @@
 
         }
 
-        synchronized public FileChannel reopenChannel() throws IOException {
+        public FileChannel reopenChannel() throws IOException {
 
-            if (raf != null && raf.getChannel().isOpen()) {
+			/*
+			 * Note: This is basically a double-checked locking pattern. It is
+			 * used to avoid synchronizing when the backing channel is already
+			 * open.
+			 */
+			{
+				final RandomAccessFile tmp = raf;
+				if (tmp != null) {
+					final FileChannel channel = tmp.getChannel();
+					if (channel.isOpen()) {
+						/*
+						 * The channel is still open. If you are allowing
+						 * concurrent reads on the channel, then this could
+						 * indicate that two readers each found the channel
+						 * closed and that one was able to re-open the channel
+						 * before the other such that the channel was open again
+						 * by the time the 2nd reader got here.
+						 */
+						return channel;
+					}
+				}
+			}
+        	
+        	synchronized(this) {
 
-                /*
-                 * The channel is still open. If you are allowing concurrent
-                 * reads on the channel, then this could indicate that two
-                 * readers each found the channel closed and that one was able
-                 * to re-open the channel before the other such that the channel
-                 * was open again by the time the 2nd reader got here.
-                 */
+				if (raf != null) {
+					final FileChannel channel = raf.getChannel();
+					if (channel.isOpen()) {
+						return channel;
+					}
+				}
 
-                return raf.getChannel();
+				// open the file.
+				this.raf = new RandomAccessFile(file, mode);
 
-            }
+				// Update counters.
+				final StoreCounters<?> c = (StoreCounters<?>) storeCounters
+						.get().acquire();
+				try {
+					c.nreopen++;
+				} finally {
+					c.release();
+				}
 
-            // open the file.
-            this.raf = new RandomAccessFile(file, mode);
+				return raf.getChannel();
 
-            // Update counters.
-            final StoreCounters<?> c = (StoreCounters<?>) storeCounters.get()
-                    .acquire();
-            try {
-                c.nreopen++;
-            } finally {
-                c.release();
-            }
-            
-            return raf.getChannel();
+			}
 
         }
 


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