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Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Wed 04 Jan 2017 13:29:09 GMT
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  iothread: add poll-grow and poll-shrink parameters
  aio: self-tune polling time
  virtio: disable virtqueue notifications during polling
  aio: add .io_poll_begin/end() callbacks
  virtio: turn vq->notification into a nested counter
  virtio-scsi: suppress virtqueue kick during processing
  virtio-blk: suppress virtqueue kick during processing
  iothread: add polling parameters
  linux-aio: poll ring for completions
  virtio: poll virtqueues for new buffers
  aio: add polling mode to AioContext
  aio: add AioPollFn and io_poll() interface
  aio: add flag to skip fds to aio_dispatch()
  HACKING: document #include order

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

include/block/aio.h

@@ -44,6 +44,7 @@ void qemu_aio_ref(void *p);
 
 typedef struct AioHandler AioHandler;
 typedef void QEMUBHFunc(void *opaque);
+typedef bool AioPollFn(void *opaque);
 typedef void IOHandler(void *opaque);
 
 struct ThreadPool;
@@ -130,6 +131,18 @@ struct AioContext {
 
     int external_disable_cnt;
 
+    /* Number of AioHandlers without .io_poll() */
+    int poll_disable_cnt;
+
+    /* Polling mode parameters */
+    int64_t poll_ns;        /* current polling time in nanoseconds */
+    int64_t poll_max_ns;    /* maximum polling time in nanoseconds */
+    int64_t poll_grow;      /* polling time growth factor */
+    int64_t poll_shrink;    /* polling time shrink factor */
+
+    /* Are we in polling mode or monitoring file descriptors? */
+    bool poll_started;
+
     /* epoll(7) state used when built with CONFIG_EPOLL */
     int epollfd;
     bool epoll_enabled;
@@ -295,8 +308,12 @@ bool aio_pending(AioContext *ctx);
 /* Dispatch any pending callbacks from the GSource attached to the AioContext.
  *
  * This is used internally in the implementation of the GSource.
+ *
+ * @dispatch_fds: true to process fds, false to skip them
+ *                (can be used as an optimization by callers that know there
+ *                are no fds ready)
  */
-bool aio_dispatch(AioContext *ctx);
+bool aio_dispatch(AioContext *ctx, bool dispatch_fds);
 
 /* Progress in completing AIO work to occur.  This can issue new pending
  * aio as a result of executing I/O completion or bh callbacks.
@@ -325,8 +342,17 @@ void aio_set_fd_handler(AioContext *ctx,
                         bool is_external,
                         IOHandler *io_read,
                         IOHandler *io_write,
+                        AioPollFn *io_poll,
                         void *opaque);
 
+/* Set polling begin/end callbacks for a file descriptor that has already been
+ * registered with aio_set_fd_handler.  Do nothing if the file descriptor is
+ * not registered.
+ */
+void aio_set_fd_poll(AioContext *ctx, int fd,
+                     IOHandler *io_poll_begin,
+                     IOHandler *io_poll_end);
+
 /* Register an event notifier and associated callbacks.  Behaves very similarly
  * to event_notifier_set_handler.  Unlike event_notifier_set_handler, these callbacks
  * will be invoked when using aio_poll().
@@ -337,7 +363,17 @@ void aio_set_fd_handler(AioContext *ctx,
 void aio_set_event_notifier(AioContext *ctx,
                             EventNotifier *notifier,
                             bool is_external,
-                            EventNotifierHandler *io_read);
+                            EventNotifierHandler *io_read,
+                            AioPollFn *io_poll);
+
+/* Set polling begin/end callbacks for an event notifier that has already been
+ * registered with aio_set_event_notifier.  Do nothing if the event notifier is
+ * not registered.
+ */
+void aio_set_event_notifier_poll(AioContext *ctx,
+                                 EventNotifier *notifier,
+                                 EventNotifierHandler *io_poll_begin,
+                                 EventNotifierHandler *io_poll_end);
 
 /* Return a GSource that lets the main loop poll the file descriptors attached
  * to this AioContext.
@@ -474,4 +510,17 @@ static inline bool aio_context_in_iothread(AioContext *ctx)
  */
 void aio_context_setup(AioContext *ctx);
 
+/**
+ * aio_context_set_poll_params:
+ * @ctx: the aio context
+ * @max_ns: how long to busy poll for, in nanoseconds
+ * @grow: polling time growth factor
+ * @shrink: polling time shrink factor
+ *
+ * Poll mode can be disabled by setting poll_max_ns to 0.
+ */
+void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
+                                 int64_t grow, int64_t shrink,
+                                 Error **errp);
+
 #endif

include/sysemu/iothread.h

@@ -28,6 +28,11 @@ typedef struct {
     QemuCond init_done_cond;    /* is thread initialization done? */
     bool stopping;
     int thread_id;
+
+    /* AioContext poll parameters */
+    int64_t poll_max_ns;
+    int64_t poll_grow;
+    int64_t poll_shrink;
 } IOThread;
 
 #define IOTHREAD(obj) \