Revamp the selector auto rebuild checker
- Count the number of select() calls made to wait until reaching at the expected dead line, and rebuild selectors if too many select() calls were made.
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Trustin Lee
parent
69e5a0eb9c
commit
19ffdd5c29
@ -352,26 +352,13 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
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/**
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* Returns the ammount of time left until the scheduled task with the closest dead line is executed.
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*/
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protected long delayNanos() {
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protected long delayNanos(long currentTimeNanos) {
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ScheduledFutureTask<?> delayedTask = delayedTaskQueue.peek();
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if (delayedTask == null) {
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return SCHEDULE_PURGE_INTERVAL;
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}
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return delayedTask.delayNanos();
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}
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/**
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* Returns the ammount of time left until the scheduled task with the closest dead line is executed.
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*/
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protected long delayMillis() {
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long delayNanos = delayNanos();
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long delayMillis = delayNanos / 1000000L;
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if (delayNanos % 1000000L < 500000L) {
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return delayMillis;
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} else {
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return delayMillis + 1;
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}
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return delayedTask.delayNanos(currentTimeNanos);
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}
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/**
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@ -763,6 +750,10 @@ public abstract class SingleThreadEventExecutor extends AbstractEventExecutor {
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return Math.max(0, deadlineNanos() - nanoTime());
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}
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public long delayNanos(long currentTimeNanos) {
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return Math.max(0, deadlineNanos() - (currentTimeNanos - START_TIME));
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}
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@Override
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public long getDelay(TimeUnit unit) {
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return unit.convert(delayNanos(), TimeUnit.NANOSECONDS);
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@ -77,7 +77,7 @@ public final class NioEventLoop extends SingleThreadEventLoop {
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}
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}
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int selectorAutoRebuildThreshold = SystemPropertyUtil.getInt("io.netty.selectorAutoRebuildThreshold", 16);
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int selectorAutoRebuildThreshold = SystemPropertyUtil.getInt("io.netty.selectorAutoRebuildThreshold", 512);
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if (selectorAutoRebuildThreshold < MIN_PREMATURE_SELECTOR_RETURNS) {
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selectorAutoRebuildThreshold = 0;
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}
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@ -108,7 +108,6 @@ public final class NioEventLoop extends SingleThreadEventLoop {
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private volatile int ioRatio = 50;
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private int cancelledKeys;
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private boolean needsToSelectAgain;
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private int prematureSelectorReturns;
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NioEventLoop(
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NioEventLoopGroup parent, ThreadFactory threadFactory, SelectorProvider selectorProvider) {
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@ -121,7 +120,6 @@ public final class NioEventLoop extends SingleThreadEventLoop {
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}
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private Selector openSelector() {
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resetPrematureSelectorReturns();
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try {
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return provider.openSelector();
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} catch (IOException e) {
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@ -548,9 +546,7 @@ public final class NioEventLoop extends SingleThreadEventLoop {
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void selectNow() throws IOException {
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try {
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if (selector.selectNow() != 0) {
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resetPrematureSelectorReturns();
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}
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selector.selectNow();
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} finally {
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// restore wakup state if needed
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if (wakenUp.get()) {
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@ -561,48 +557,52 @@ public final class NioEventLoop extends SingleThreadEventLoop {
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private void select() throws IOException {
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Selector selector = this.selector;
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long delayMillis = delayMillis();
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try {
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if (delayMillis > 0) {
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long startTimeNanos = System.nanoTime();
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if (selector.select(delayMillis) == 0) {
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if (oldWakenUp || wakenUp.get() || hasTasks()) {
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// Waken up by user or the task queue has a pending task.
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return;
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int selectCnt = 0;
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long currentTimeNanos = System.nanoTime();
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long selectDeadLineNanos = currentTimeNanos + delayNanos(currentTimeNanos);
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for (;;) {
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long timeoutMillis = (selectDeadLineNanos - currentTimeNanos + 500000L) / 1000000L;
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if (timeoutMillis <= 0) {
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if (selectCnt == 0) {
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selector.selectNow();
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selectCnt = 1;
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}
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long delayNanos = delayNanos();
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if (delayNanos <= 0) {
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// Waken up to handle a delayed task.
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return;
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}
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if (System.nanoTime() - startTimeNanos < delayNanos >>> 1) {
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// Returned way before the specified timeout with no selected keys.
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// This may be because of the JDK /dev/epoll bug - increment the counter.
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prematureSelectorReturns ++;
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if (SELECTOR_AUTO_REBUILD_THRESHOLD > 0 &&
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prematureSelectorReturns >= SELECTOR_AUTO_REBUILD_THRESHOLD) {
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// The selector returned prematurely many times in a row.
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// Rebuild the selector to work around the problem.
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logger.warn(
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"Selector.select() returned prematurely {} times in a row; rebuilding selector.",
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prematureSelectorReturns);
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rebuildSelector();
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// Select again to populate selectedKeys.
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selector.selectNow();
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}
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} else {
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resetPrematureSelectorReturns();
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}
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} else {
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resetPrematureSelectorReturns();
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break;
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}
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} else {
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if (selector.selectNow() != 0) {
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resetPrematureSelectorReturns();
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int selectedKeys = selector.select(timeoutMillis);
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selectCnt ++;
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if (selectedKeys != 0 || oldWakenUp || wakenUp.get() || hasTasks()) {
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// Selected something,
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// waken up by user, or
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// the task queue has a pending task.
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break;
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}
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if (SELECTOR_AUTO_REBUILD_THRESHOLD > 0 &&
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selectCnt >= SELECTOR_AUTO_REBUILD_THRESHOLD) {
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// The selector returned prematurely many times in a row.
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// Rebuild the selector to work around the problem.
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logger.warn(
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"Selector.select() returned prematurely {} times in a row; rebuilding selector.",
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selectCnt);
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rebuildSelector();
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// Select again to populate selectedKeys.
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selector.selectNow();
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selectCnt = 1;
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break;
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}
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currentTimeNanos = System.nanoTime();
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}
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if (selectCnt > MIN_PREMATURE_SELECTOR_RETURNS) {
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if (logger.isDebugEnabled()) {
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logger.debug("Selector.select() returned prematurely {} times in a row.", selectCnt - 1);
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}
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}
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} catch (CancelledKeyException e) {
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@ -616,21 +616,9 @@ public final class NioEventLoop extends SingleThreadEventLoop {
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private void selectAgain() {
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needsToSelectAgain = false;
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try {
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if (selector.selectNow() != 0) {
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resetPrematureSelectorReturns();
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}
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selector.selectNow();
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} catch (Throwable t) {
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logger.warn("Failed to update SelectionKeys.", t);
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}
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}
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private void resetPrematureSelectorReturns() {
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int prematureSelectorReturns = this.prematureSelectorReturns;
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if (prematureSelectorReturns >= MIN_PREMATURE_SELECTOR_RETURNS) {
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if (logger.isDebugEnabled()) {
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logger.debug("Selector.select() returned prematurely {} times in a row.", prematureSelectorReturns);
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}
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this.prematureSelectorReturns = 0;
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}
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}
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}
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@ -377,7 +377,7 @@ public class SingleThreadEventLoopTest {
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protected void run() {
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for (;;) {
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try {
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Thread.sleep(TimeUnit.NANOSECONDS.toMillis(delayNanos()));
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Thread.sleep(TimeUnit.NANOSECONDS.toMillis(delayNanos(System.nanoTime())));
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} catch (InterruptedException e) {
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// Waken up by interruptThread()
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}
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