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Enable automatic selector rebuilding by default

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- Fixes #1192
- Log at WARN level for easier diagnosis
This commit is contained in:
Trustin Lee 2013-03-22 11:48:41 +09:00
parent fa02ffddae
commit 1ab2813405
1 changed files with 64 additions and 53 deletions
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117
transport/src/main/java/io/netty/channel/nio/NioEventLoop.java
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@ -39,7 +39,6 @@ import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
@ -57,11 +56,8 @@ public final class NioEventLoop extends SingleThreadEventLoop {
private static final int CLEANUP_INTERVAL = 256; // XXX Hard-coded value, but won't need customization.
private static final boolean EPOLL_BUG_WORKAROUND =
SystemPropertyUtil.getBoolean("io.netty.epollBugWorkaround", false);
private static final long SELECT_TIMEOUT = SystemPropertyUtil.getLong("io.netty.selectTimeout", 500);
private static final long SELECT_TIMEOUT_NANOS = TimeUnit.MILLISECONDS.toNanos(SELECT_TIMEOUT);
private static final int SELECTOR_AUTO_REBUILD_THRESHOLD =
SystemPropertyUtil.getInt("io.netty.selectorAutoRebuildThreshold", 16);
// Workaround for JDK NIO bug.
//
@ -80,9 +76,9 @@ public final class NioEventLoop extends SingleThreadEventLoop {
logger.debug("Unable to get/set System Property '" + key + '\'', e);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Using select timeout of " + SELECT_TIMEOUT);
logger.debug("Epoll-bug workaround enabled = " + EPOLL_BUG_WORKAROUND);
logger.debug("Selector auto-rebuild threshold: {}", SELECTOR_AUTO_REBUILD_THRESHOLD);
}
}
@ -104,6 +100,7 @@ public final class NioEventLoop extends SingleThreadEventLoop {
private volatile int ioRatio = 50;
private int cancelledKeys;
private boolean needsToSelectAgain;
private int prematureSelectorReturns;
NioEventLoop(
NioEventLoopGroup parent, ThreadFactory threadFactory, SelectorProvider selectorProvider) {
@ -116,6 +113,7 @@ public final class NioEventLoop extends SingleThreadEventLoop {
}
private Selector openSelector() {
resetPrematureSelectorReturns();
try {
return provider.openSelector();
} catch (IOException e) {
@ -219,7 +217,7 @@ public final class NioEventLoop extends SingleThreadEventLoop {
}
try {
newSelector = Selector.open();
newSelector = openSelector();
} catch (Exception e) {
logger.warn("Failed to create a new Selector.", e);
return;
@ -276,12 +274,6 @@ public final class NioEventLoop extends SingleThreadEventLoop {
@Override
protected void run() {
// use 80% of the timeout for measure
final long minSelectTimeout = SELECT_TIMEOUT_NANOS / 100 * 80;
Selector selector = this.selector;
int selectReturnsImmediately = 0;
for (;;) {
wakenUp.set(false);
@ -289,35 +281,7 @@ public final class NioEventLoop extends SingleThreadEventLoop {
if (hasTasks()) {
selectNow();
} else {
long beforeSelect = System.nanoTime();
int selected = select();
if (EPOLL_BUG_WORKAROUND) {
if (selected == 0) {
long timeBlocked = System.nanoTime() - beforeSelect;
if (timeBlocked < minSelectTimeout) {
// returned before the minSelectTimeout elapsed with nothing select.
// this may be the cause of the jdk epoll(..) bug, so increment the counter
// which we use later to see if its really the jdk bug.
selectReturnsImmediately ++;
} else {
selectReturnsImmediately = 0;
}
if (selectReturnsImmediately == 10) {
// The selector returned immediately for 10 times in a row,
// so recreate one selector as it seems like we hit the
// famous epoll(..) jdk bug.
rebuildSelector();
selector = this.selector;
selectReturnsImmediately = 0;
// try to select again
continue;
}
} else {
// reset counter
selectReturnsImmediately = 0;
}
}
select();
// 'wakenUp.compareAndSet(false, true)' is always evaluated
// before calling 'selector.wakeup()' to reduce the wake-up
@ -356,12 +320,10 @@ public final class NioEventLoop extends SingleThreadEventLoop {
final long ioStartTime = System.nanoTime();
processSelectedKeys();
selector = this.selector;
final long ioTime = System.nanoTime() - ioStartTime;
final int ioRatio = this.ioRatio;
runAllTasks(ioTime * (100 - ioRatio) / ioRatio);
selector = this.selector;
if (isShutdown()) {
closeAll();
@ -579,7 +541,9 @@ public final class NioEventLoop extends SingleThreadEventLoop {
void selectNow() throws IOException {
try {
selector.selectNow();
if (selector.selectNow() != 0) {
resetPrematureSelectorReturns();
}
} finally {
// restore wakup state if needed
if (wakenUp.get()) {
@ -588,13 +552,50 @@ public final class NioEventLoop extends SingleThreadEventLoop {
}
}
private int select() throws IOException {
private void select() throws IOException {
Selector selector = this.selector;
long delayMillis = delayMillis();
try {
if (delayMillis > 0) {
return selector.select(delayMillis);
long startTimeNanos = System.nanoTime();
if (selector.select(delayMillis) == 0) {
if (wakenUp.get() || hasTasks()) {
// Waken up by user or the task queue has a pending task.
return;
}
long delayNanos = delayNanos();
if (delayNanos <= 0) {
// Waken up to handle a delayed task.
return;
}
if (System.nanoTime() - startTimeNanos < delayNanos >>> 1) {
// Returned way before the specified timeout with no selected keys.
// This may be because of the JDK /dev/epoll bug - increment the counter.
if (++ prematureSelectorReturns >= SELECTOR_AUTO_REBUILD_THRESHOLD) {
// The selector returned prematurely many times in a row.
// Rebuild the selector to work around the problem.
logger.warn(
"Selector.select() returned prematurely {} times in a row; rebuilding selector.",
prematureSelectorReturns);
rebuildSelector();
selector = this.selector;
// Select again to populate selectedKeys.
selector.selectNow();
}
} else {
resetPrematureSelectorReturns();
}
} else {
// reset counter
resetPrematureSelectorReturns();
}
} else {
return selector.selectNow();
if (selector.selectNow() != 0) {
resetPrematureSelectorReturns();
}
}
} catch (CancelledKeyException e) {
if (logger.isDebugEnabled()) {
@ -604,16 +605,26 @@ public final class NioEventLoop extends SingleThreadEventLoop {
}
// Harmless exception - log anyway
}
return -1;
}
private void selectAgain() {
needsToSelectAgain = false;
try {
selector.selectNow();
if (selector.selectNow() != 0) {
resetPrematureSelectorReturns();
}
} catch (Throwable t) {
logger.warn("Failed to update SelectionKeys.", t);
}
}
private void resetPrematureSelectorReturns() {
int prematureSelectorReturns = this.prematureSelectorReturns;
if (prematureSelectorReturns != 0) {
if (logger.isWarnEnabled()) {
logger.warn("Selector.select() returned prematurely {} times in a row.", prematureSelectorReturns);
}
this.prematureSelectorReturns = 0;
}
}
}