Add posixaio_waitcomplete engine.

Provide a variant of the posixaio engine that uses FreeBSD's
aio_waitcomplete() function to consume completions, instead of running
around polling all IOs with aio_error().

Signed-off-by: Thomas Munro <thomas.munro@gmail.com>

Author: macdice

HOWTO

@@ -1945,6 +1945,11 @@ I/O engine
 			POSIX asynchronous I/O using :manpage:`aio_read(3)` and
 			:manpage:`aio_write(3)`.
 
+		**posixaio_waitcomplete**
+			POSIX asynchronous I/O, using FreeBSD's
+			aio_waitcomplete(2) to get completion events from the
+			kernel.
+
 		**solarisaio**
 			Solaris native asynchronous I/O.
 

configure

@@ -737,6 +737,26 @@ EOF
 fi
 print_config "POSIX AIO fsync" "$posix_aio_fsync"
 
+##########################################
+# aio_waitcomplete probe
+if test "have_aio_waitcomplete" != "yes" ; then
+  have_aio_waitcomplete="no"
+fi
+cat > $TMPC <<EOF
+#include <aio.h>
+#include <stdlib.h>
+int main(void)
+{
+  struct aiocb *cb;
+  aio_waitcomplete(&cb, NULL);
+  return 0;
+}
+EOF
+if compile_prog "" "" "aio_waitcomplete" ; then
+  have_aio_waitcomplete="yes"
+fi
+print_config "aio_waitcomplete()" "$have_aio_waitcomplete"
+
 ##########################################
 # POSIX pshared attribute probe
 if test "$posix_pshared" != "yes" ; then
@@ -2858,6 +2878,9 @@ fi
 if test "$posix_aio_fsync" = "yes" ; then
   output_sym "CONFIG_POSIXAIO_FSYNC"
 fi
+if test "$have_aio_waitcomplete" = "yes" ; then
+  output_sym "CONFIG_HAVE_AIO_WAITCOMPLETE"
+fi
 if test "$posix_pshared" = "yes" ; then
   output_sym "CONFIG_PSHARED"
 fi

engines/posixaio.c

@@ -55,6 +55,59 @@ static int fio_posixaio_prep(struct thread_data fio_unused *td,
 	return 0;
 }
 
+#ifdef CONFIG_HAVE_AIO_WAITCOMPLETE
+
+static int fio_posixaio_waitcomplete_getevents(struct thread_data *td,
+					       unsigned int min,
+					       unsigned int max,
+					       const struct timespec *t)
+{
+	struct posixaio_data *pd = td->io_ops_data;
+	struct aiocb *aiocb;
+	struct io_u *io_u;
+	ssize_t retval;
+	unsigned int events = 0;
+	struct timespec zero_timeout = {0};
+	struct timespec *timeout;
+
+	do
+	{
+		if (events < min) {
+			/* Wait until the minimum is satisfied. */
+			timeout = (struct timespec *)t;
+		} else {
+			/* Consume as many more as we can without waiting. */
+			timeout = &zero_timeout;
+		}
+
+		retval = aio_waitcomplete(&aiocb, timeout);
+		if (retval < 0) {
+			if (errno == EINTR)
+				continue;
+			if (errno == EAGAIN)
+				break;
+			td_verror(td, errno, "aio_waitcomplete");
+			break;
+		}
+
+		io_u = container_of(aiocb, struct io_u, aiocb);
+		pd->queued--;
+		pd->aio_events[events++] = io_u;
+
+		if (retval >= 0)
+			io_u->resid = io_u->xfer_buflen - retval;
+		else if (errno == ECANCELED)
+			io_u->resid = io_u->xfer_buflen;
+		else
+			io_u->error = errno;
+
+	} while (events < max && pd->queued > 0);
+
+	return events;
+}
+
+#endif
+
 #define SUSPEND_ENTRIES	8
 
 static int fio_posixaio_getevents(struct thread_data *td, unsigned int min,
@@ -223,12 +276,36 @@ static struct ioengine_ops ioengine = {
 	.get_file_size	= generic_get_file_size,
 };
 
+#ifdef CONFIG_HAVE_AIO_WAITCOMPLETE
+static struct ioengine_ops ioengine_waitcomplete = {
+	.name		= "posixaio_waitcomplete",
+	.version	= FIO_IOOPS_VERSION,
+	.flags		= FIO_ASYNCIO_SYNC_TRIM,
+	.init		= fio_posixaio_init,
+	.prep		= fio_posixaio_prep,
+	.queue		= fio_posixaio_queue,
+	.cancel		= fio_posixaio_cancel,
+	.getevents	= fio_posixaio_waitcomplete_getevents,
+	.event		= fio_posixaio_event,
+	.cleanup	= fio_posixaio_cleanup,
+	.open_file	= generic_open_file,
+	.close_file	= generic_close_file,
+	.get_file_size	= generic_get_file_size,
+};
+#endif
+
 static void fio_init fio_posixaio_register(void)
 {
 	register_ioengine(&ioengine);
+#ifdef CONFIG_HAVE_AIO_WAITCOMPLETE
+	register_ioengine(&ioengine_waitcomplete);
+#endif
 }
 
 static void fio_exit fio_posixaio_unregister(void)
 {
 	unregister_ioengine(&ioengine);
+#ifdef CONFIG_HAVE_AIO_WAITCOMPLETE
+	unregister_ioengine(&ioengine_waitcomplete);
+#endif
 }

fio.1

@@ -1739,6 +1739,11 @@ This engine defines engine specific options.
 POSIX asynchronous I/O using \fBaio_read\fR\|(3) and
 \fBaio_write\fR\|(3).
 .TP
+.B posixaio_waitcomplete
+POSIX asynchronous I/O using \fBaio_read\fR\|(3) and
+\fBaio_write\fR\|(3), with FreeBSD \fBaio_waitcomplete\fR\|(2)
+to consume completion events.
+.TP
 .B solarisaio
 Solaris native asynchronous I/O.
 .TP