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Exploit blocking FAST_POLL for eventfd reads (#10543)

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Motivation

If we make eventfd blocking then read can take the place of poll+read

Modification

Make eventfd blocking, use READ instead of POLLIN, allocating a static
64bit buffer to read into

Result

Fewer kernel roundtrips for event loop wakeups
This commit is contained in:
Nick Hill 2020-09-09 22:37:39 -07:00 committed by GitHub
parent d933a9dd56
commit 2316c2ce45
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 28 additions and 44 deletions
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20
transport-native-io_uring/src/main/c/netty_io_uring_native.c
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@ -178,8 +178,9 @@ static jint netty_io_uring_enter(JNIEnv *env, jclass class1, jint ring_fd, jint
return -err;
}
static jint netty_epoll_native_eventFd(JNIEnv* env, jclass clazz) {
jint eventFD = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
static jint netty_epoll_native_blocking_event_fd(JNIEnv* env, jclass clazz) {
// We use a blocking fd with io_uring FAST_POLL read
jint eventFD = eventfd(0, EFD_CLOEXEC);
if (eventFD < 0) {
netty_unix_errors_throwChannelExceptionErrorNo(env, "eventfd() failed: ", errno);
@ -210,16 +211,6 @@ static jint netty_io_uring_unregister_event_fd(JNIEnv *env, jclass class1, jint
return 0;
}
static void netty_io_uring_eventFdRead(JNIEnv* env, jclass clazz, jint fd) {
uint64_t eventfd_t;
if (eventfd_read(fd, &eventfd_t) != 0) {
// something is serious wrong
netty_unix_errors_throwRuntimeException(env, "eventfd_read() failed");
}
}
static void netty_io_uring_eventFdWrite(JNIEnv* env, jclass clazz, jint fd, jlong value) {
uint64_t val;
@ -438,9 +429,8 @@ static const JNINativeMethod method_table[] = {
{"ioUringExit", "(Lio/netty/channel/uring/RingBuffer;)V", (void *) netty_io_uring_ring_buffer_exit},
{"createFile", "()I", (void *) netty_create_file},
{"ioUringEnter", "(IIII)I", (void *)netty_io_uring_enter},
{"eventFd", "()I", (void *) netty_epoll_native_eventFd},
{"blockingEventFd", "()I", (void *) netty_epoll_native_blocking_event_fd},
{"eventFdWrite", "(IJ)V", (void *) netty_io_uring_eventFdWrite },
{"eventFdRead", "(I)V", (void *) netty_io_uring_eventFdRead },
{"ioUringRegisterEventFd", "(II)I", (void *) netty_io_uring_register_event_fd},
{"ioUringUnregisterEventFd", "(I)I", (void *) netty_io_uring_unregister_event_fd}
};
@ -593,4 +583,4 @@ JNIEXPORT void JNI_OnUnload(JavaVM* vm, void* reserved) {
return;
}
netty_io_uring_native_JNI_OnUnLoad(env);
}
}

38
transport-native-io_uring/src/main/java/io/netty/channel/uring/IOUringEventLoop.java
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@ -35,6 +35,8 @@ final class IOUringEventLoop extends SingleThreadEventLoop implements
IOUringCompletionQueue.IOUringCompletionQueueCallback {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(IOUringEventLoop.class);
private final long eventfdReadBuf = PlatformDependent.allocateMemory(8);
private final IntObjectMap<AbstractIOUringChannel> channels = new IntObjectHashMap<AbstractIOUringChannel>(4096);
private final RingBuffer ringBuffer;
@ -69,7 +71,7 @@ final class IOUringEventLoop extends SingleThreadEventLoop implements
}
});
eventfd = Native.newEventFd();
eventfd = Native.newBlockingEventFd();
logger.trace("New EventLoop: {}", this.toString());
}
@ -122,7 +124,7 @@ final class IOUringEventLoop extends SingleThreadEventLoop implements
final IOUringSubmissionQueue submissionQueue = ringBuffer.getIoUringSubmissionQueue();
// Lets add the eventfd related events before starting to do any real work.
submissionQueue.addPollIn(eventfd.intValue());
addEventFdRead(submissionQueue);
submissionQueue.submit();
for (;;) {
@ -181,23 +183,21 @@ final class IOUringEventLoop extends SingleThreadEventLoop implements
@Override
public boolean handle(int fd, int res, long flags, int op, int pollMask) {
IOUringSubmissionQueue submissionQueue = ringBuffer.getIoUringSubmissionQueue();
final AbstractIOUringChannel channel;
if (op == Native.IORING_OP_READ || op == Native.IORING_OP_ACCEPT) {
channel = handleRead(fd, res);
if (eventfd.intValue() == fd) {
channel = null;
if (res != Native.ERRNO_ECANCELED_NEGATIVE) {
pendingWakeup = false;
addEventFdRead(ringBuffer.getIoUringSubmissionQueue());
}
} else {
channel = handleRead(fd, res);
}
} else if (op == Native.IORING_OP_WRITEV || op == Native.IORING_OP_WRITE) {
channel = handleWrite(fd, res);
} else if (op == Native.IORING_OP_POLL_ADD) {
if (eventfd.intValue() == fd) {
if (res == Native.ERRNO_ECANCELED_NEGATIVE) {
return true;
}
channel = null;
pendingWakeup = false;
handleEventFd(submissionQueue);
} else {
channel = handlePollAdd(fd, res, pollMask);
}
channel = handlePollAdd(fd, res, pollMask);
} else if (op == Native.IORING_OP_POLL_REMOVE) {
if (res == Errors.ERRNO_ENOENT_NEGATIVE) {
logger.trace("IORING_POLL_REMOVE not successful");
@ -258,13 +258,8 @@ final class IOUringEventLoop extends SingleThreadEventLoop implements
return channel;
}
private void handleEventFd(IOUringSubmissionQueue submissionQueue) {
// We need to consume the data as otherwise we would see another event
// in the completionQueue without
// an extra eventfd_write(....)
Native.eventFdRead(eventfd.intValue());
submissionQueue.addPollIn(eventfd.intValue());
private void addEventFdRead(IOUringSubmissionQueue submissionQueue) {
submissionQueue.addRead(eventfd.intValue(), eventfdReadBuf, 0, 8);
}
private AbstractIOUringChannel handleConnect(int fd, int res) {
@ -284,6 +279,7 @@ final class IOUringEventLoop extends SingleThreadEventLoop implements
}
ringBuffer.close();
iovArrays.release();
PlatformDependent.freeMemory(eventfdReadBuf);
}
public RingBuffer getRingBuffer() {

8
transport-native-io_uring/src/main/java/io/netty/channel/uring/Native.java
View File

@ -111,15 +111,13 @@ final class Native {
public static native void eventFdWrite(int fd, long value);
public static native void eventFdRead(int fd);
public static FileDescriptor newEventFd() {
return new FileDescriptor(eventFd());
public static FileDescriptor newBlockingEventFd() {
return new FileDescriptor(blockingEventFd());
}
public static native void ioUringExit(RingBuffer ringBuffer);
private static native int eventFd();
private static native int blockingEventFd();
// for testing(it is only temporary)
public static native int createFile();

6
transport-native-io_uring/src/test/java/io/netty/channel/uring/NativeTest.java
View File

@ -144,7 +144,7 @@ public class NativeTest {
assertNotNull(submissionQueue);
assertNotNull(completionQueue);
final FileDescriptor eventFd = Native.newEventFd();
final FileDescriptor eventFd = Native.newBlockingEventFd();
assertFalse(submissionQueue.addPollIn(eventFd.intValue()));
submissionQueue.submit();
@ -198,7 +198,7 @@ public class NativeTest {
}
};
waitingCqe.start();
final FileDescriptor eventFd = Native.newEventFd();
final FileDescriptor eventFd = Native.newBlockingEventFd();
assertFalse(submissionQueue.addPollIn(eventFd.intValue()));
submissionQueue.submit();
@ -231,7 +231,7 @@ public class NativeTest {
IOUringSubmissionQueue submissionQueue = ringBuffer.getIoUringSubmissionQueue();
final IOUringCompletionQueue completionQueue = ringBuffer.getIoUringCompletionQueue();
FileDescriptor eventFd = Native.newEventFd();
FileDescriptor eventFd = Native.newBlockingEventFd();
submissionQueue.addPollIn(eventFd.intValue());
submissionQueue.submit();
submissionQueue.addPollRemove(eventFd.intValue(), Native.POLLIN);