Suspected regression: fix for 6735255 causes delay in GC of ZipFile InputStreams, increase in heap demand
Neil Richards
neil.richards at ngmr.net
Thu Apr 7 13:30:23 UTC 2011
On Mon, 2011-04-04 at 09:04 +1000, David Holmes wrote:
> 1. If a call to close() occurs around the same time as finalization
> occurs then the finalizer thread will set inFinalizer to true, at which
> point the thread executing close() can see it is true and so may skip
> the releaseInflater(inf) call.
>
> 2. As isClosed is not volatile, and available() is not synchronized, a
> thread calling available() on a closed stream may not see that it has
> been closed and so will likely encounter an IOException rather than
> getting a zero return.
>
>
> Even if #1 is not a practical problem I'd be inclined to make the
> finalizer synchronized as well. By doing that you're effectively
> ensuring that premature finalization of the stream won't happen.
I tend to agree, especially as it also makes the intention of the code
clearer.
>
> For #2 it is a tricky call. If you don't actually expect the stream
> object to be used by multiple threads then using a synchronized block to
> read isClosed will be cheap in VMs that go to great effort to reduce the
> cost of unnecessary synchronization (eg biased-locking in hotspot).
> Otherwise making isClosed volatile is likely the better option.
The check at the start of available() guards the logic beyond (which
uses a value from the inflater object, which would not be valid if the
stream has been closed()).
Because of this, I think it would be clearer to synchronize the
available() method too.
As you say, it is extremely likely that, in practice, this
synchronization will never be contended, and so won't impact performance
significantly (in modern VMs).
Please find below an updated changeset with these modifications,
Thanks for your advice in this,
Neil
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IBM email: neil_richards at uk.ibm.com
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# HG changeset patch
# User Neil Richards <neil.richards at ngmr.net>, <neil_richards at uk.ibm.com>
# Date 1300289208 0
# Branch zip-heap
# Node ID db52003c128c8706f45e0b2bf9f98d5e905d2090
# Parent 554adcfb615e63e62af530b1c10fcf7813a75b26
7031076: Retained ZipFile InputStreams increase heap demand
Summary: Allow unreferenced ZipFile InputStreams to be finalized, GC'd
Contributed-by: <neil.richards at ngmr.net>
diff -r 554adcfb615e -r db52003c128c src/share/classes/java/util/zip/ZipFile.java
--- a/src/share/classes/java/util/zip/ZipFile.java Wed Mar 16 15:01:07 2011 -0700
+++ b/src/share/classes/java/util/zip/ZipFile.java Wed Mar 16 15:26:48 2011 +0000
@@ -30,11 +30,14 @@
import java.io.IOException;
import java.io.EOFException;
import java.io.File;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
import java.nio.charset.Charset;
import java.util.Vector;
import java.util.Enumeration;
import java.util.Set;
import java.util.HashSet;
+import java.util.Iterator;
import java.util.NoSuchElementException;
import java.security.AccessController;
import sun.security.action.GetPropertyAction;
@@ -315,7 +318,16 @@
private static native void freeEntry(long jzfile, long jzentry);
// the outstanding inputstreams that need to be closed.
- private Set<InputStream> streams = new HashSet<>();
+ private final Set<WeakReference<InputStream>> streams = new HashSet<>();
+ private final ReferenceQueue<? super InputStream> staleStreamQueue =
+ new ReferenceQueue<>();
+
+ private void clearStaleStreams() {
+ Object staleStream;
+ while (null != (staleStream = staleStreamQueue.poll())) {
+ streams.remove(staleStream);
+ }
+ }
/**
* Returns an input stream for reading the contents of the specified
@@ -339,6 +351,7 @@
ZipFileInputStream in = null;
synchronized (this) {
ensureOpen();
+ clearStaleStreams();
if (!zc.isUTF8() && (entry.flag & EFS) != 0) {
jzentry = getEntry(jzfile, zc.getBytesUTF8(entry.name), false);
} else {
@@ -351,51 +364,19 @@
switch (getEntryMethod(jzentry)) {
case STORED:
- streams.add(in);
+ streams.add(
+ new WeakReference<InputStream>(in, staleStreamQueue));
return in;
case DEFLATED:
- final ZipFileInputStream zfin = in;
// MORE: Compute good size for inflater stream:
long size = getEntrySize(jzentry) + 2; // Inflater likes a bit of slack
if (size > 65536) size = 8192;
if (size <= 0) size = 4096;
- InputStream is = new InflaterInputStream(zfin, getInflater(), (int)size) {
- private boolean isClosed = false;
-
- public void close() throws IOException {
- if (!isClosed) {
- super.close();
- releaseInflater(inf);
- isClosed = true;
- }
- }
- // Override fill() method to provide an extra "dummy" byte
- // at the end of the input stream. This is required when
- // using the "nowrap" Inflater option.
- protected void fill() throws IOException {
- if (eof) {
- throw new EOFException(
- "Unexpected end of ZLIB input stream");
- }
- len = this.in.read(buf, 0, buf.length);
- if (len == -1) {
- buf[0] = 0;
- len = 1;
- eof = true;
- }
- inf.setInput(buf, 0, len);
- }
- private boolean eof;
-
- public int available() throws IOException {
- if (isClosed)
- return 0;
- long avail = zfin.size() - inf.getBytesWritten();
- return avail > (long) Integer.MAX_VALUE ?
- Integer.MAX_VALUE : (int) avail;
- }
- };
- streams.add(is);
+ InputStream is =
+ new ZipFileInflaterInputStream(in, getInflater(),
+ (int)size);
+ streams.add(
+ new WeakReference<InputStream>(is, staleStreamQueue));
return is;
default:
throw new ZipException("invalid compression method");
@@ -403,6 +384,56 @@
}
}
+ private class ZipFileInflaterInputStream extends InflaterInputStream {
+ private boolean isClosed = false;
+ private boolean eof = false;
+ private final ZipFileInputStream zfin;
+ private boolean inFinalizer = false;
+
+ ZipFileInflaterInputStream(ZipFileInputStream zfin, Inflater inf,
+ int size) {
+ super(zfin, inf, size);
+ this.zfin = zfin;
+ }
+
+ public synchronized void close() throws IOException {
+ if (!isClosed) {
+ super.close();
+ if (false == inFinalizer)
+ releaseInflater(inf);
+ isClosed = true;
+ }
+ }
+ // Override fill() method to provide an extra "dummy" byte
+ // at the end of the input stream. This is required when
+ // using the "nowrap" Inflater option.
+ protected void fill() throws IOException {
+ if (eof) {
+ throw new EOFException("Unexpected end of ZLIB input stream");
+ }
+ len = in.read(buf, 0, buf.length);
+ if (len == -1) {
+ buf[0] = 0;
+ len = 1;
+ eof = true;
+ }
+ inf.setInput(buf, 0, len);
+ }
+
+ public synchronized int available() throws IOException {
+ if (isClosed)
+ return 0;
+ long avail = zfin.size() - inf.getBytesWritten();
+ return (avail > (long) Integer.MAX_VALUE ?
+ Integer.MAX_VALUE : (int) avail);
+ }
+
+ protected synchronized void finalize() throws IOException {
+ inFinalizer = true;
+ close();
+ }
+ }
+
/*
* Gets an inflater from the list of available inflaters or allocates
* a new one.
@@ -543,11 +574,14 @@
synchronized (this) {
closeRequested = true;
- if (streams.size() !=0) {
- Set<InputStream> copy = streams;
- streams = new HashSet<>();
- for (InputStream is: copy)
+ Iterator<WeakReference<InputStream>> streamsIterator =
+ streams.iterator();
+ while (streamsIterator.hasNext()) {
+ InputStream is = streamsIterator.next().get();
+ if (null != is) {
is.close();
+ }
+ streamsIterator.remove();
}
if (jzfile != 0) {
@@ -684,9 +718,12 @@
freeEntry(ZipFile.this.jzfile, jzentry);
jzentry = 0;
}
- streams.remove(this);
}
}
+
+ protected void finalize() {
+ close();
+ }
}
diff -r 554adcfb615e -r db52003c128c test/java/util/zip/ZipFile/ClearStaleZipFileInputStreams.java
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/java/util/zip/ZipFile/ClearStaleZipFileInputStreams.java Wed Mar 16 15:26:48 2011 +0000
@@ -0,0 +1,148 @@
+/*
+ * Copyright (c) 2011 Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * Portions Copyright (c) 2011 IBM Corporation
+ */
+
+/*
+ * @test
+ * @bug 7031076
+ * @summary Allow stale InputStreams from ZipFiles to be GC'd
+ * @author Neil Richards <neil.richards at ngmr.net>, <neil_richards at uk.ibm.com>
+ */
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.InputStream;
+import java.util.Enumeration;
+import java.util.HashSet;
+import java.util.Random;
+import java.util.Set;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+import java.util.zip.ZipOutputStream;
+
+public class ClearStaleZipFileInputStreams {
+ private static final int ZIP_ENTRY_NUM = 5;
+
+ private static final byte[][] data;
+
+ static {
+ data = new byte[ZIP_ENTRY_NUM][];
+ Random r = new Random();
+ for (int i = 0; i < ZIP_ENTRY_NUM; i++) {
+ data[i] = new byte[1000];
+ r.nextBytes(data[i]);
+ }
+ }
+
+ private static File createTestFile(int compression) throws Exception {
+ File tempZipFile =
+ File.createTempFile("test-data" + compression, ".zip");
+ tempZipFile.deleteOnExit();
+
+ ZipOutputStream zos =
+ new ZipOutputStream(new FileOutputStream(tempZipFile));
+ zos.setLevel(compression);
+
+ try {
+ for (int i = 0; i < ZIP_ENTRY_NUM; i++) {
+ String text = "Entry" + i;
+ ZipEntry entry = new ZipEntry(text);
+ zos.putNextEntry(entry);
+ try {
+ zos.write(data[i], 0, data[i].length);
+ } finally {
+ zos.closeEntry();
+ }
+ }
+ } finally {
+ zos.close();
+ }
+
+ return tempZipFile;
+ }
+
+ private static void startGcInducingThread(final int sleepMillis) {
+ final Thread gcInducingThread = new Thread() {
+ public void run() {
+ while (true) {
+ System.gc();
+ try {
+ Thread.sleep(sleepMillis);
+ } catch (InterruptedException e) { }
+ }
+ }
+ };
+
+ gcInducingThread.setDaemon(true);
+ gcInducingThread.start();
+ }
+
+ public static void main(String[] args) throws Exception {
+ startGcInducingThread(500);
+ runTest(ZipOutputStream.DEFLATED);
+ runTest(ZipOutputStream.STORED);
+ }
+
+ private static void runTest(int compression) throws Exception {
+ ReferenceQueue<InputStream> rq = new ReferenceQueue<>();
+
+ System.out.println("Testing with a zip file with compression level = "
+ + compression);
+ File f = createTestFile(compression);
+ try {
+ ZipFile zf = new ZipFile(f);
+ try {
+ Set<Object> refSet = createTransientInputStreams(zf, rq);
+
+ System.out.println("Waiting for 'stale' input streams from ZipFile to be GC'd ...");
+ System.out.println("(The test will hang on failure)");
+ while (false == refSet.isEmpty()) {
+ refSet.remove(rq.remove());
+ }
+ System.out.println("Test PASSED.");
+ System.out.println();
+ } finally {
+ zf.close();
+ }
+ } finally {
+ f.delete();
+ }
+ }
+
+ private static Set<Object> createTransientInputStreams(ZipFile zf,
+ ReferenceQueue<InputStream> rq) throws Exception {
+ Enumeration<? extends ZipEntry> zfe = zf.entries();
+ Set<Object> refSet = new HashSet<>();
+
+ while (zfe.hasMoreElements()) {
+ InputStream is = zf.getInputStream(zfe.nextElement());
+ refSet.add(new WeakReference<InputStream>(is, rq));
+ }
+
+ return refSet;
+ }
+}
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