diff --git a/buffer.c b/buffer.c
index 098afec3..8d0038c7 100644
--- a/buffer.c
+++ b/buffer.c
@@ -575,7 +575,8 @@ evbuffer_reserve_space(struct evbuffer *buf, ev_ssize_t size,
 	} else {
 		if (_evbuffer_expand_fast(buf, size, n_vecs)<0)
 			goto done;
-		n = _evbuffer_read_setup_vecs(buf, size, vec, n_vecs, &chainp, 0);
+		n = _evbuffer_read_setup_vecs(buf, size, vec, n_vecs,
+				&chainp, 0);
 	}
 
 done:
@@ -670,6 +671,12 @@ done:
 	return result;
 }
 
+static inline int
+HAS_PINNED_R(struct evbuffer *buf)
+{
+	return (buf->last && CHAIN_PINNED_R(buf->last));
+}
+
 static inline void
 ZERO_CHAIN(struct evbuffer *dst)
 {
@@ -680,6 +687,71 @@ ZERO_CHAIN(struct evbuffer *dst)
 	dst->total_len = 0;
 }
 
+/* Prepares the contents of src to be moved to another buffer by removing
+ * read-pinned chains. The first pinned chain is saved in first, and the
+ * last in last. If src has no read-pinned chains, first and last are set
+ * to NULL. */
+static int
+PRESERVE_PINNED(struct evbuffer *src, struct evbuffer_chain **first,
+		struct evbuffer_chain **last)
+{
+	struct evbuffer_chain *chain, **pinned;
+
+	ASSERT_EVBUFFER_LOCKED(src);
+
+	if (!HAS_PINNED_R(src)) {
+		*first = *last = NULL;
+		return 0;
+	}
+
+	pinned = src->last_with_datap;
+	if (!CHAIN_PINNED_R(*pinned))
+		pinned = &(*pinned)->next;
+	EVUTIL_ASSERT(CHAIN_PINNED_R(*pinned));
+	chain = *first = *pinned;
+	*last = src->last;
+
+	/* If there's data in the first pinned chain, we need to allocate
+	 * a new chain and copy the data over. */
+	if (chain->off) {
+		struct evbuffer_chain *tmp;
+
+		EVUTIL_ASSERT(pinned == src->last_with_datap);
+		tmp = evbuffer_chain_new(chain->off);
+		if (!tmp)
+			return -1;
+		memcpy(tmp->buffer, chain->buffer + chain->misalign,
+			chain->off);
+		tmp->off = chain->off;
+		*src->last_with_datap = tmp;
+		src->last = tmp;
+		chain->misalign += chain->off;
+		chain->off = 0;
+	} else {
+		src->last = *src->last_with_datap;
+		*pinned = NULL;
+	}
+
+	return 0;
+}
+
+static inline void
+RESTORE_PINNED(struct evbuffer *src, struct evbuffer_chain *pinned,
+		struct evbuffer_chain *last)
+{
+	ASSERT_EVBUFFER_LOCKED(src);
+
+	if (!pinned) {
+		ZERO_CHAIN(src);
+		return;
+	}
+
+	src->first = pinned;
+	src->last = last;
+	src->last_with_datap = &src->first;
+	src->total_len = 0;
+}
+
 static inline void
 COPY_CHAIN(struct evbuffer *dst, struct evbuffer *src)
 {
@@ -729,6 +801,7 @@ PREPEND_CHAIN(struct evbuffer *dst, struct evbuffer *src)
 int
 evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 {
+	struct evbuffer_chain *pinned, *last;
 	size_t in_total_len, out_total_len;
 	int result = 0;
 
@@ -744,6 +817,11 @@ evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 		goto done;
 	}
 
+	if (PRESERVE_PINNED(inbuf, &pinned, &last) < 0) {
+		result = -1;
+		goto done;
+	}
+
 	if (out_total_len == 0) {
 		/* There might be an empty chain at the start of outbuf; free
 		 * it. */
@@ -753,8 +831,8 @@ evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 		APPEND_CHAIN(outbuf, inbuf);
 	}
 
-	/* remove everything from inbuf */
-	ZERO_CHAIN(inbuf);
+	RESTORE_PINNED(inbuf, pinned, last);
+
 	inbuf->n_del_for_cb += in_total_len;
 	outbuf->n_add_for_cb += in_total_len;
 
@@ -769,6 +847,7 @@ done:
 int
 evbuffer_prepend_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 {
+	struct evbuffer_chain *pinned, *last;
 	size_t in_total_len, out_total_len;
 	int result = 0;
 
@@ -785,6 +864,11 @@ evbuffer_prepend_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 		goto done;
 	}
 
+	if (PRESERVE_PINNED(inbuf, &pinned, &last) < 0) {
+		result = -1;
+		goto done;
+	}
+
 	if (out_total_len == 0) {
 		/* There might be an empty chain at the start of outbuf; free
 		 * it. */
@@ -794,8 +878,8 @@ evbuffer_prepend_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 		PREPEND_CHAIN(outbuf, inbuf);
 	}
 
-	/* remove everything from inbuf */
-	ZERO_CHAIN(inbuf);
+	RESTORE_PINNED(inbuf, pinned, last);
+
 	inbuf->n_del_for_cb += in_total_len;
 	outbuf->n_add_for_cb += in_total_len;
 
@@ -810,7 +894,7 @@ int
 evbuffer_drain(struct evbuffer *buf, size_t len)
 {
 	struct evbuffer_chain *chain, *next;
-	size_t old_len;
+	size_t remaining, old_len;
 	int result = 0;
 
 	EVBUFFER_LOCK(buf);
@@ -824,12 +908,10 @@ evbuffer_drain(struct evbuffer *buf, size_t len)
 		goto done;
 	}
 
-
-	if (len >= old_len && !(buf->last && CHAIN_PINNED_R(buf->last))) {
+	if (len >= old_len && !HAS_PINNED_R(buf)) {
 		len = old_len;
 		for (chain = buf->first; chain != NULL; chain = next) {
 			next = chain->next;
-
 			evbuffer_chain_free(chain);
 		}
 
@@ -839,10 +921,12 @@ evbuffer_drain(struct evbuffer *buf, size_t len)
 			len = old_len;
 
 		buf->total_len -= len;
-
-		for (chain = buf->first; len >= chain->off; chain = next) {
+		remaining = len;
+		for (chain = buf->first;
+		     remaining >= chain->off;
+		     chain = next) {
 			next = chain->next;
-			len -= chain->off;
+			remaining -= chain->off;
 
 			if (chain == *buf->last_with_datap) {
 				buf->last_with_datap = &buf->first;
@@ -850,14 +934,20 @@ evbuffer_drain(struct evbuffer *buf, size_t len)
 			if (&chain->next == buf->last_with_datap)
 				buf->last_with_datap = &buf->first;
 
-			if (len == 0 && CHAIN_PINNED_R(chain))
+			if (CHAIN_PINNED_R(chain)) {
+				EVUTIL_ASSERT(remaining == 0);
+				chain->misalign += chain->off;
+				chain->off = 0;
 				break;
-			evbuffer_chain_free(chain);
+			} else
+				evbuffer_chain_free(chain);
 		}
 
 		buf->first = chain;
-		chain->misalign += len;
-		chain->off -= len;
+		if (chain) {
+			chain->misalign += remaining;
+			chain->off -= remaining;
+		}
 	}
 
 	buf->n_del_for_cb += len;
diff --git a/buffer_iocp.c b/buffer_iocp.c
index 8255599c..e211e980 100644
--- a/buffer_iocp.c
+++ b/buffer_iocp.c
@@ -82,12 +82,13 @@ static void
 pin_release(struct evbuffer_overlapped *eo, unsigned flag)
 {
 	int i;
-	struct evbuffer_chain *chain = eo->first_pinned;
+	struct evbuffer_chain *next, *chain = eo->first_pinned;
 
 	for (i = 0; i < eo->n_buffers; ++i) {
 		EVUTIL_ASSERT(chain);
+		next = chain->next;
 		_evbuffer_chain_unpin(chain, flag);
-		chain = chain->next;
+		chain = next;
 	}
 }
 
@@ -95,8 +96,9 @@ void
 evbuffer_commit_read(struct evbuffer *evbuf, ev_ssize_t nBytes)
 {
 	struct evbuffer_overlapped *buf = upcast_evbuffer(evbuf);
-	struct evbuffer_iovec iov[2];
-	int n_vec;
+	struct evbuffer_chain **chainp;
+	size_t remaining, len;
+	unsigned i;
 
 	EVBUFFER_LOCK(evbuf);
 	EVUTIL_ASSERT(buf->read_in_progress && !buf->write_in_progress);
@@ -104,24 +106,27 @@ evbuffer_commit_read(struct evbuffer *evbuf, ev_ssize_t nBytes)
 
 	evbuffer_unfreeze(evbuf, 0);
 
-	iov[0].iov_base = buf->buffers[0].buf;
-	if ((size_t)nBytes <= buf->buffers[0].len) {
-		iov[0].iov_len = nBytes;
-		n_vec = 1;
-	} else {
-		iov[0].iov_len = buf->buffers[0].len;
-		iov[1].iov_base = buf->buffers[1].buf;
-		iov[1].iov_len = nBytes - iov[0].iov_len;
-		n_vec = 2;
+	chainp = evbuf->last_with_datap;
+	if (!((*chainp)->flags & EVBUFFER_MEM_PINNED_R))
+		chainp = &(*chainp)->next;
+	remaining = nBytes;
+	for (i = 0; remaining > 0 && i < buf->n_buffers; ++i) {
+		EVUTIL_ASSERT(*chainp);
+		len = buf->buffers[i].len;
+		if (remaining < len)
+			len = remaining;
+		(*chainp)->off += len;
+		evbuf->last_with_datap = chainp;
+		remaining -= len;
+		chainp = &(*chainp)->next;
 	}
 
-	if (evbuffer_commit_space(evbuf, iov, n_vec) < 0)
-		EVUTIL_ASSERT(0); /* XXXX fail nicer. */
-
 	pin_release(buf, EVBUFFER_MEM_PINNED_R);
 
 	buf->read_in_progress = 0;
 
+	evbuf->total_len += nBytes;
+
 	_evbuffer_decref_and_unlock(evbuf);
 }
 
@@ -184,7 +189,7 @@ evbuffer_launch_write(struct evbuffer *buf, ev_ssize_t at_most,
 	}
 	evbuffer_freeze(buf, 1);
 
-	buf_o->first_pinned = 0;
+	buf_o->first_pinned = NULL;
 	buf_o->n_buffers = 0;
 	memset(buf_o->buffers, 0, sizeof(buf_o->buffers));
 
@@ -246,19 +251,16 @@ evbuffer_launch_read(struct evbuffer *buf, size_t at_most,
 	if (buf->freeze_end || buf_o->read_in_progress)
 		goto done;
 
-	buf_o->first_pinned = 0;
+	buf_o->first_pinned = NULL;
 	buf_o->n_buffers = 0;
 	memset(buf_o->buffers, 0, sizeof(buf_o->buffers));
 
-	if (_evbuffer_expand_fast(buf, at_most, 2) == -1)
+	if (_evbuffer_expand_fast(buf, at_most, MAX_WSABUFS) == -1)
 		goto done;
 	evbuffer_freeze(buf, 0);
 
-	/* XXX This and evbuffer_read_setup_vecs() should say MAX_WSABUFS,
-	 * not "2".  But commit_read() above can't handle more than two
-	 * buffers yet. */
 	nvecs = _evbuffer_read_setup_vecs(buf, at_most,
-	    vecs, 2, &chainp, 1);
+	    vecs, MAX_WSABUFS, &chainp, 1);
 	for (i=0;i<nvecs;++i) {
 		WSABUF_FROM_EVBUFFER_IOV(
 			&buf_o->buffers[i],
@@ -266,7 +268,8 @@ evbuffer_launch_read(struct evbuffer *buf, size_t at_most,
 	}
 
 	buf_o->n_buffers = nvecs;
-	buf_o->first_pinned = chain= *chainp;
+	buf_o->first_pinned = chain = *chainp;
+
 	npin=0;
 	for ( ; chain; chain = chain->next) {
 		_evbuffer_chain_pin(chain, EVBUFFER_MEM_PINNED_R);
diff --git a/bufferevent.c b/bufferevent.c
index 9923bbe0..53b07f1f 100644
--- a/bufferevent.c
+++ b/bufferevent.c
@@ -206,10 +206,11 @@ bufferevent_run_deferred_callbacks_unlocked(struct deferred_cb *_, void *arg)
 
 #define SCHEDULE_DEFERRED(bevp)						\
 	do {								\
+		bufferevent_incref(&(bevp)->bev);			\
 		event_deferred_cb_schedule(				\
 			event_base_get_deferred_cb_queue((bevp)->bev.ev_base), \
 			&(bevp)->deferred);				\
-	} while (0);
+	} while (0)
 
 
 void
@@ -222,10 +223,8 @@ _bufferevent_run_readcb(struct bufferevent *bufev)
 		return;
 	if (p->options & BEV_OPT_DEFER_CALLBACKS) {
 		p->readcb_pending = 1;
-		if (!p->deferred.queued) {
-			bufferevent_incref(bufev);
+		if (!p->deferred.queued)
 			SCHEDULE_DEFERRED(p);
-		}
 	} else {
 		bufev->readcb(bufev, bufev->cbarg);
 	}
@@ -241,10 +240,8 @@ _bufferevent_run_writecb(struct bufferevent *bufev)
 		return;
 	if (p->options & BEV_OPT_DEFER_CALLBACKS) {
 		p->writecb_pending = 1;
-		if (!p->deferred.queued) {
-			bufferevent_incref(bufev);
+		if (!p->deferred.queued)
 			SCHEDULE_DEFERRED(p);
-		}
 	} else {
 		bufev->writecb(bufev, bufev->cbarg);
 	}
@@ -261,10 +258,8 @@ _bufferevent_run_eventcb(struct bufferevent *bufev, short what)
 	if (p->options & BEV_OPT_DEFER_CALLBACKS) {
 		p->eventcb_pending |= what;
 		p->errno_pending = EVUTIL_SOCKET_ERROR();
-		if (!p->deferred.queued) {
-			bufferevent_incref(bufev);
+		if (!p->deferred.queued)
 			SCHEDULE_DEFERRED(p);
-		}
 	} else {
 		bufev->errorcb(bufev, what, bufev->cbarg);
 	}
diff --git a/bufferevent_async.c b/bufferevent_async.c
index 23b636d2..fa1bbc92 100644
--- a/bufferevent_async.c
+++ b/bufferevent_async.c
@@ -48,11 +48,15 @@
 #include <ws2tcpip.h>
 #endif
 
+#include <sys/queue.h>
+
 #include "event2/util.h"
 #include "event2/bufferevent.h"
 #include "event2/buffer.h"
 #include "event2/bufferevent_struct.h"
 #include "event2/event.h"
+#include "event2/util.h"
+#include "event-internal.h"
 #include "log-internal.h"
 #include "mm-internal.h"
 #include "bufferevent-internal.h"
@@ -74,6 +78,8 @@ struct bufferevent_async {
 	unsigned read_in_progress : 1;
 	unsigned write_in_progress : 1;
 	unsigned ok : 1;
+	unsigned read_added : 1;
+	unsigned write_added : 1;
 };
 
 const struct bufferevent_ops bufferevent_ops_async = {
@@ -125,74 +131,143 @@ upcast_write(struct event_overlapped *eo)
 }
 
 static void
-bev_async_consider_writing(struct bufferevent_async *b)
+bev_async_del_write(struct bufferevent_async *beva)
 {
-	size_t at_most;
-	int limit;
-	/* Don't write if there's a write in progress, or we do not
-	 * want to write. */
-	if (!b->ok || b->write_in_progress || !(b->bev.bev.enabled&EV_WRITE))
-		return;
-	/* Don't write if there's nothing to write */
-	if (!evbuffer_get_length(b->bev.bev.output))
-		return;
+	struct bufferevent *bev = &beva->bev.bev;
 
-	at_most = evbuffer_get_length(b->bev.bev.output);
-
-	/* XXXX This over-commits. */
-	limit = _bufferevent_get_write_max(&b->bev);
-	if (at_most >= limit)
-		at_most = limit;
-
-	if (b->bev.write_suspended)
-		return;
-
-	/*  XXXX doesn't respect low-water mark very well. */
-	if (evbuffer_launch_write(b->bev.bev.output, at_most,
-	    &b->write_overlapped)) {
-		EVUTIL_ASSERT(0);/* XXX act sensibly. */
-	} else {
-		b->write_in_progress = 1;
+	if (beva->write_added) {
+		beva->write_added = 0;
+		event_base_del_virtual(bev->ev_base);
 	}
 }
 
 static void
-bev_async_consider_reading(struct bufferevent_async *b)
+bev_async_del_read(struct bufferevent_async *beva)
+{
+	struct bufferevent *bev = &beva->bev.bev;
+
+	if (beva->read_added) {
+		beva->read_added = 0;
+		event_base_del_virtual(bev->ev_base);
+	}
+}
+
+static void
+bev_async_add_write(struct bufferevent_async *beva)
+{
+	struct bufferevent *bev = &beva->bev.bev;
+
+	if (!beva->write_added) {
+		beva->write_added = 1;
+		event_base_add_virtual(bev->ev_base);
+	}
+}
+
+static void
+bev_async_add_read(struct bufferevent_async *beva)
+{
+	struct bufferevent *bev = &beva->bev.bev;
+
+	if (!beva->read_added) {
+		beva->read_added = 1;
+		event_base_add_virtual(bev->ev_base);
+	}
+}
+
+static void
+bev_async_consider_writing(struct bufferevent_async *beva)
+{
+	size_t at_most;
+	int limit;
+	struct bufferevent *bev = &beva->bev.bev;
+
+	/* Don't write if there's a write in progress, or we do not
+	 * want to write, or when there's nothing left to write. */
+	if (beva->write_in_progress)
+		return;
+	if (!beva->ok || !(bev->enabled&EV_WRITE) ||
+	    !evbuffer_get_length(bev->output)) {
+		bev_async_del_write(beva);
+		return;
+	}
+
+	at_most = evbuffer_get_length(bev->output);
+
+	/* XXXX This over-commits. */
+	limit = _bufferevent_get_write_max(&beva->bev);
+	if (at_most >= limit)
+		at_most = limit;
+
+	if (beva->bev.write_suspended) {
+		bev_async_del_write(beva);
+		return;
+	}
+
+	/*  XXXX doesn't respect low-water mark very well. */
+	bufferevent_incref(bev);
+	if (evbuffer_launch_write(bev->output, at_most,
+	    &beva->write_overlapped)) {
+		bufferevent_decref(bev);
+		beva->ok = 0;
+		_bufferevent_run_eventcb(bev, BEV_EVENT_ERROR);
+	} else {
+		beva->write_in_progress = 1;
+		bev_async_add_write(beva);
+	}
+}
+
+static void
+bev_async_consider_reading(struct bufferevent_async *beva)
 {
 	size_t cur_size;
 	size_t read_high;
 	size_t at_most;
 	int limit;
+	struct bufferevent *bev = &beva->bev.bev;
+
 	/* Don't read if there is a read in progress, or we do not
 	 * want to read. */
-	if (!b->ok || b->read_in_progress || !(b->bev.bev.enabled&EV_READ))
+	if (beva->read_in_progress)
 		return;
+	if (!beva->ok || !(bev->enabled&EV_READ)) {
+		bev_async_del_read(beva);
+		return;
+	}
 
 	/* Don't read if we're full */
-	cur_size = evbuffer_get_length(b->bev.bev.input);
-	read_high = b->bev.bev.wm_read.high;
+	cur_size = evbuffer_get_length(bev->input);
+	read_high = bev->wm_read.high;
 	if (read_high) {
-		if (cur_size >= read_high)
+		if (cur_size >= read_high) {
+			bev_async_del_read(beva);
 			return;
+		}
 		at_most = read_high - cur_size;
 	} else {
 		at_most = 16384; /* FIXME totally magic. */
 	}
 
 	/* XXXX This over-commits. */
-	limit = _bufferevent_get_read_max(&b->bev);
+	limit = _bufferevent_get_read_max(&beva->bev);
 	if (at_most >= limit)
 		at_most = limit;
 
-	if (b->bev.read_suspended)
+	if (beva->bev.read_suspended) {
+		bev_async_del_read(beva);
 		return;
-
-	if (evbuffer_launch_read(b->bev.bev.input, at_most,
-	    &b->read_overlapped)) {
-		EVUTIL_ASSERT(0);
-	} else {
-		b->read_in_progress = 1;
 	}
+
+	bufferevent_incref(bev);
+	if (evbuffer_launch_read(bev->input, at_most, &beva->read_overlapped)) {
+		beva->ok = 0;
+		bufferevent_decref(bev);
+		_bufferevent_run_eventcb(bev, BEV_EVENT_ERROR);
+	} else {
+		beva->read_in_progress = 1;
+		bev_async_add_read(beva);
+	}
+
+	return;
 }
 
 static void
@@ -260,14 +335,19 @@ be_async_enable(struct bufferevent *buf, short what)
 static int
 be_async_disable(struct bufferevent *bev, short what)
 {
+	struct bufferevent_async *bev_async = upcast(bev);
 	/* XXXX If we disable reading or writing, we may want to consider
 	 * canceling any in-progress read or write operation, though it might
 	 * not work. */
 
-	if (what & EV_READ)
+	if (what & EV_READ) {
 		BEV_DEL_GENERIC_READ_TIMEOUT(bev);
-	if (what & EV_WRITE)
+		bev_async_del_read(bev_async);
+	}
+	if (what & EV_WRITE) {
 		BEV_DEL_GENERIC_WRITE_TIMEOUT(bev);
+		bev_async_del_write(bev_async);
+	}
 
 	return 0;
 }
@@ -275,18 +355,36 @@ be_async_disable(struct bufferevent *bev, short what)
 static void
 be_async_destruct(struct bufferevent *bev)
 {
+	struct bufferevent_async *bev_async = upcast(bev);
 	struct bufferevent_private *bev_p = BEV_UPCAST(bev);
 	evutil_socket_t fd;
 
-	EVUTIL_ASSERT(!upcast(bev)->write_in_progress && !upcast(bev)->read_in_progress);
+	EVUTIL_ASSERT(!upcast(bev)->write_in_progress &&
+			!upcast(bev)->read_in_progress);
+
+	bev_async_del_read(bev_async);
+	bev_async_del_write(bev_async);
 
-	/* XXX cancel any outstanding I/O operations */
 	fd = _evbuffer_overlapped_get_fd(bev->input);
-	/* delete this in case non-blocking connect was used */
-	event_del(&bev->ev_write);
 	if (bev_p->options & BEV_OPT_CLOSE_ON_FREE)
 		evutil_closesocket(fd);
-	_bufferevent_del_generic_timeout_cbs(bev);
+	/* delete this in case non-blocking connect was used */
+	if (event_initialized(&bev->ev_write)) {
+		event_del(&bev->ev_write);
+		_bufferevent_del_generic_timeout_cbs(bev);
+	}
+}
+
+/* GetQueuedCompletionStatus doesn't reliably yield WSA error codes, so
+ * we use WSAGetOverlappedResult to translate. */
+static void
+bev_async_set_wsa_error(struct bufferevent *bev, struct event_overlapped *eo)
+{
+	DWORD bytes, flags;
+	evutil_socket_t fd;
+
+	fd = _evbuffer_overlapped_get_fd(bev->input);
+	WSAGetOverlappedResult(fd, &eo->overlapped, &bytes, FALSE, &flags);
 }
 
 static int
@@ -303,15 +401,22 @@ connect_complete(struct event_overlapped *eo, ev_uintptr_t key,
 	struct bufferevent_async *bev_a = upcast_connect(eo);
 	struct bufferevent *bev = &bev_a->bev.bev;
 
-	_bufferevent_incref_and_lock(bev);
+	BEV_LOCK(bev);
 
 	EVUTIL_ASSERT(bev_a->bev.connecting);
 	bev_a->bev.connecting = 0;
+	event_base_del_virtual(bev->ev_base);
+
+	if (ok)
+		bufferevent_async_set_connected(bev);
+	else
+		bev_async_set_wsa_error(bev, eo);
 
-	bufferevent_async_set_connected(bev);
 	_bufferevent_run_eventcb(bev,
 			ok? BEV_EVENT_CONNECTED : BEV_EVENT_ERROR);
 
+	event_base_del_virtual(bev->ev_base);
+
 	_bufferevent_decref_and_unlock(bev);
 }
 
@@ -323,26 +428,32 @@ read_complete(struct event_overlapped *eo, ev_uintptr_t key,
 	struct bufferevent *bev = &bev_a->bev.bev;
 	short what = BEV_EVENT_READING;
 
-	_bufferevent_incref_and_lock(bev);
-	EVUTIL_ASSERT(bev_a->ok && bev_a->read_in_progress);
+	BEV_LOCK(bev);
+	EVUTIL_ASSERT(bev_a->read_in_progress);
 
 	evbuffer_commit_read(bev->input, nbytes);
 	bev_a->read_in_progress = 0;
 
-	if (ok && nbytes) {
-		BEV_RESET_GENERIC_READ_TIMEOUT(bev);
-		_bufferevent_decrement_read_buckets(&bev_a->bev, nbytes);
-		if (evbuffer_get_length(bev->input) >= bev->wm_read.low)
-			_bufferevent_run_readcb(bev);
-		bev_async_consider_reading(bev_a);
-	} else if (!ok) {
-		what |= BEV_EVENT_ERROR;
-		bev_a->ok = 0;
-		_bufferevent_run_eventcb(bev, what);
-	} else if (!nbytes) {
-		what |= BEV_EVENT_EOF;
-		bev_a->ok = 0;
-		_bufferevent_run_eventcb(bev, what);
+	if (!ok)
+		bev_async_set_wsa_error(bev, eo);
+
+	if (bev_a->ok) {
+		if (ok && nbytes) {
+			BEV_RESET_GENERIC_READ_TIMEOUT(bev);
+			_bufferevent_decrement_read_buckets(&bev_a->bev,
+					nbytes);
+			if (evbuffer_get_length(bev->input) >= bev->wm_read.low)
+				_bufferevent_run_readcb(bev);
+			bev_async_consider_reading(bev_a);
+		} else if (!ok) {
+			what |= BEV_EVENT_ERROR;
+			bev_a->ok = 0;
+			_bufferevent_run_eventcb(bev, what);
+		} else if (!nbytes) {
+			what |= BEV_EVENT_EOF;
+			bev_a->ok = 0;
+			_bufferevent_run_eventcb(bev, what);
+		}
 	}
 
 	_bufferevent_decref_and_unlock(bev);
@@ -356,26 +467,32 @@ write_complete(struct event_overlapped *eo, ev_uintptr_t key,
 	struct bufferevent *bev = &bev_a->bev.bev;
 	short what = BEV_EVENT_WRITING;
 
-	_bufferevent_incref_and_lock(bev);
-	EVUTIL_ASSERT(bev_a->ok && bev_a->write_in_progress);
-
+	BEV_LOCK(bev);
+	EVUTIL_ASSERT(bev_a->write_in_progress);
 	evbuffer_commit_write(bev->output, nbytes);
 	bev_a->write_in_progress = 0;
 
-	if (ok && nbytes) {
-		BEV_RESET_GENERIC_WRITE_TIMEOUT(bev);
-		_bufferevent_decrement_write_buckets(&bev_a->bev, nbytes);
-		if (evbuffer_get_length(bev->output) <= bev->wm_write.low)
-			_bufferevent_run_writecb(bev);
-		bev_async_consider_writing(bev_a);
-	} else if (!ok) {
-		what |= BEV_EVENT_ERROR;
-		bev_a->ok = 0;
-		_bufferevent_run_eventcb(bev, what);
-	} else if (!nbytes) {
-		what |= BEV_EVENT_EOF;
-		bev_a->ok = 0;
-		_bufferevent_run_eventcb(bev, what);
+	if (!ok)
+		bev_async_set_wsa_error(bev, eo);
+
+	if (bev_a->ok) {
+		if (ok && nbytes) {
+			BEV_RESET_GENERIC_WRITE_TIMEOUT(bev);
+			_bufferevent_decrement_write_buckets(&bev_a->bev,
+					nbytes);
+			if (evbuffer_get_length(bev->output) <=
+			    bev->wm_write.low)
+				_bufferevent_run_writecb(bev);
+			bev_async_consider_writing(bev_a);
+		} else if (!ok) {
+			what |= BEV_EVENT_ERROR;
+			bev_a->ok = 0;
+			_bufferevent_run_eventcb(bev, what);
+		} else if (!nbytes) {
+			what |= BEV_EVENT_EOF;
+			bev_a->ok = 0;
+			_bufferevent_run_eventcb(bev, what);
+		}
 	}
 
 	_bufferevent_decref_and_unlock(bev);
@@ -423,8 +540,6 @@ bufferevent_async_new(struct event_base *base,
 
 	evbuffer_add_cb(bev->input, be_async_inbuf_callback, bev);
 	evbuffer_add_cb(bev->output, be_async_outbuf_callback, bev);
-	evbuffer_defer_callbacks(bev->input, base);
-	evbuffer_defer_callbacks(bev->output, base);
 
 	event_overlapped_init(&bev_a->connect_overlapped, connect_complete);
 	event_overlapped_init(&bev_a->read_overlapped, read_complete);
@@ -497,11 +612,16 @@ bufferevent_async_connect(struct bufferevent *bev, evutil_socket_t fd,
 	    WSAGetLastError() != WSAEINVAL)
 		return -1;
 
+	event_base_add_virtual(bev->ev_base);
+	bufferevent_incref(bev);
 	rc = ext->ConnectEx(fd, sa, socklen, NULL, 0, NULL,
 			    &bev_async->connect_overlapped.overlapped);
 	if (rc || WSAGetLastError() == ERROR_IO_PENDING)
 		return 0;
 
+	event_base_del_virtual(bev->ev_base);
+	bufferevent_decref(bev);
+
 	return -1;
 }
 
diff --git a/evbuffer-internal.h b/evbuffer-internal.h
index 90fd1b55..719e85dd 100644
--- a/evbuffer-internal.h
+++ b/evbuffer-internal.h
@@ -256,7 +256,8 @@ int _evbuffer_expand_fast(struct evbuffer *, size_t, int);
  * Returns the number of vecs used.
  */
 int _evbuffer_read_setup_vecs(struct evbuffer *buf, ev_ssize_t howmuch,
-    struct evbuffer_iovec *vecs, int n_vecs, struct evbuffer_chain ***chainp, int exact);
+    struct evbuffer_iovec *vecs, int n_vecs, struct evbuffer_chain ***chainp,
+    int exact);
 
 /* Helper macro: copies an evbuffer_iovec in ei to a win32 WSABUF in i. */
 #define WSABUF_FROM_EVBUFFER_IOV(i,ei) do {		\
diff --git a/event-internal.h b/event-internal.h
index 122195b3..0f891657 100644
--- a/event-internal.h
+++ b/event-internal.h
@@ -182,6 +182,8 @@ struct event_base {
 	/** Data to implement the common signal handelr code. */
 	struct evsig_info sig;
 
+	/** Number of virtual events */
+	int virtual_event_count;
 	/** Number of total events added to this event_base */
 	int event_count;
 	/** Number of total events active in this event_base */
@@ -286,6 +288,7 @@ struct event_config_entry {
 struct event_config {
 	TAILQ_HEAD(event_configq, event_config_entry) entries;
 
+	int n_cpus_hint;
 	enum event_method_feature require_features;
 	enum event_base_config_flag flags;
 };
@@ -316,6 +319,10 @@ int _evsig_restore_handler(struct event_base *base, int evsignal);
 
 void event_active_nolock(struct event *ev, int res, short count);
 
+/* FIXME document. */
+void event_base_add_virtual(struct event_base *base);
+void event_base_del_virtual(struct event_base *base);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/event.c b/event.c
index 902aed54..7ecbfc1e 100644
--- a/event.c
+++ b/event.c
@@ -615,19 +615,19 @@ event_base_new_with_config(const struct event_config *cfg)
 
 #ifdef WIN32
 	if (cfg && (cfg->flags & EVENT_BASE_FLAG_STARTUP_IOCP))
-		event_base_start_iocp(base);
+		event_base_start_iocp(base, cfg->n_cpus_hint);
 #endif
 
 	return (base);
 }
 
 int
-event_base_start_iocp(struct event_base *base)
+event_base_start_iocp(struct event_base *base, int n_cpus)
 {
 #ifdef WIN32
 	if (base->iocp)
 		return 0;
-	base->iocp = event_iocp_port_launch();
+	base->iocp = event_iocp_port_launch(n_cpus);
 	if (!base->iocp) {
 		event_warnx("%s: Couldn't launch IOCP", __func__);
 		return -1;
@@ -638,6 +638,20 @@ event_base_start_iocp(struct event_base *base)
 #endif
 }
 
+void
+event_base_stop_iocp(struct event_base *base)
+{
+#ifdef WIN32
+	int rv;
+
+	if (!base->iocp)
+		return;
+	rv = event_iocp_shutdown(base->iocp, -1);
+	EVUTIL_ASSERT(rv >= 0);
+	base->iocp = NULL;
+#endif
+}
+
 void
 event_base_free(struct event_base *base)
 {
@@ -654,6 +668,10 @@ event_base_free(struct event_base *base)
 	/* XXX(niels) - check for internal events first */
 	EVUTIL_ASSERT(base);
 
+#ifdef WIN32
+	event_base_stop_iocp(base);
+#endif
+
 	/* threading fds if we have them */
 	if (base->th_notify_fd[0] != -1) {
 		event_del(&base->th_notify);
@@ -921,6 +939,15 @@ event_config_require_features(struct event_config *cfg,
 	return (0);
 }
 
+int
+event_config_set_num_cpus_hint(struct event_config *cfg, int cpus)
+{
+	if (!cfg)
+		return (-1);
+	cfg->n_cpus_hint = cpus;
+	return (0);
+}
+
 int
 event_priority_init(int npriorities)
 {
@@ -965,7 +992,7 @@ static int
 event_haveevents(struct event_base *base)
 {
 	/* Caller must hold th_base_lock */
-	return (base->event_count > 0);
+	return (base->virtual_event_count > 0 || base->event_count > 0);
 }
 
 /* "closure" function called when processing active signal events */
@@ -1279,9 +1306,10 @@ event_process_active_single_queue(struct event_base *base,
 }
 
 /*
-   Process all the defered_cb entries in 'queue'.  If *breakptr becomes set to
-   1, stop.  Requires that we start out holding the lock on 'queue'; releases
-   the lock around 'queue' for each deferred_cb we process.
+   Process up to MAX_DEFERRED of the defered_cb entries in 'queue'.  If
+   *breakptr becomes set to 1, stop.  Requires that we start out holding
+   the lock on 'queue'; releases the lock around 'queue' for each deferred_cb
+   we process.
  */
 static int
 event_process_deferred_callbacks(struct deferred_cb_queue *queue, int *breakptr)
@@ -1289,6 +1317,7 @@ event_process_deferred_callbacks(struct deferred_cb_queue *queue, int *breakptr)
 	int count = 0;
 	struct deferred_cb *cb;
 
+#define MAX_DEFERRED 16
 	while ((cb = TAILQ_FIRST(&queue->deferred_cb_list))) {
 		cb->queued = 0;
 		TAILQ_REMOVE(&queue->deferred_cb_list, cb, cb_next);
@@ -1296,12 +1325,14 @@ event_process_deferred_callbacks(struct deferred_cb_queue *queue, int *breakptr)
 		UNLOCK_DEFERRED_QUEUE(queue);
 
 		cb->cb(cb, cb->arg);
-		++count;
-		if (*breakptr)
-			return -1;
 
 		LOCK_DEFERRED_QUEUE(queue);
+		if (*breakptr)
+			return -1;
+		if (++count == MAX_DEFERRED)
+			break;
 	}
+#undef MAX_DEFERRED
 	return count;
 }
 
@@ -2723,3 +2754,19 @@ event_base_dump_events(struct event_base *base, FILE *output)
 		}
 	}
 }
+
+void
+event_base_add_virtual(struct event_base *base)
+{
+	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
+	base->virtual_event_count++;
+	EVBASE_RELEASE_LOCK(base, th_base_lock);
+}
+
+void
+event_base_del_virtual(struct event_base *base)
+{
+	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
+	base->virtual_event_count--;
+	EVBASE_RELEASE_LOCK(base, th_base_lock);
+}
diff --git a/event_iocp.c b/event_iocp.c
index fe9ea571..254ed90d 100644
--- a/event_iocp.c
+++ b/event_iocp.c
@@ -36,6 +36,7 @@
 #include "log-internal.h"
 #include "mm-internal.h"
 #include "event-internal.h"
+#include "evthread-internal.h"
 
 #define NOTIFICATION_KEY ((ULONG_PTR)-1)
 
@@ -73,7 +74,8 @@ loop(void *_port)
 		EnterCriticalSection(&port->lock);
 		if (port->shutdown) {
 			if (--port->n_live_threads == 0)
-				ReleaseSemaphore(port->shutdownSemaphore, 1, NULL);
+				ReleaseSemaphore(port->shutdownSemaphore, 1,
+						NULL);
 			LeaveCriticalSection(&port->lock);
 			return;
 		}
@@ -160,8 +162,10 @@ event_get_win32_extension_fns(void)
 	return &the_extension_fns;
 }
 
+#define N_CPUS_DEFAULT 2
+
 struct event_iocp_port *
-event_iocp_port_launch(void)
+event_iocp_port_launch(int n_cpus)
 {
 	struct event_iocp_port *port;
 	int i;
@@ -171,12 +175,16 @@ event_iocp_port_launch(void)
 
 	if (!(port = mm_calloc(1, sizeof(struct event_iocp_port))))
 		return NULL;
-	port->n_threads = 2;
+
+	if (n_cpus <= 0)
+		n_cpus = N_CPUS_DEFAULT;
+	port->n_threads = n_cpus * 2;
 	port->threads = calloc(port->n_threads, sizeof(HANDLE));
 	if (!port->threads)
 		goto err;
 
-	port->port = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, port->n_threads);
+	port->port = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0,
+			n_cpus);
 	port->ms = -1;
 	if (!port->port)
 		goto err;
@@ -233,13 +241,18 @@ event_iocp_notify_all(struct event_iocp_port *port)
 int
 event_iocp_shutdown(struct event_iocp_port *port, long waitMsec)
 {
+	DWORD ms = INFINITE;
 	int n;
+
 	EnterCriticalSection(&port->lock);
 	port->shutdown = 1;
 	LeaveCriticalSection(&port->lock);
 	event_iocp_notify_all(port);
 
-	WaitForSingleObject(port->shutdownSemaphore, waitMsec);
+	if (waitMsec >= 0)
+		ms = waitMsec;
+
+	WaitForSingleObject(port->shutdownSemaphore, ms);
 	EnterCriticalSection(&port->lock);
 	n = port->n_live_threads;
 	LeaveCriticalSection(&port->lock);
@@ -271,4 +284,3 @@ event_base_get_iocp(struct event_base *base)
 	return NULL;
 #endif
 }
-
diff --git a/include/event2/event.h b/include/event2/event.h
index e9d0048f..fa0f625d 100644
--- a/include/event2/event.h
+++ b/include/event2/event.h
@@ -226,6 +226,16 @@ int event_config_require_features(struct event_config *cfg, int feature);
  * will be initialized, and how they'll work. */
 int event_config_set_flag(struct event_config *cfg, int flag);
 
+/**
+ * Records a hint for the number of CPUs in the system. This is used for
+ * tuning thread pools, etc, for optimal performance.
+ *
+ * @param cfg the event configuration object
+ * @param cpus the number of cpus
+ * @return 0 on success, -1 on failure.
+ */
+int event_config_set_num_cpus_hint(struct event_config *cfg, int cpus);
+
 /**
   Initialize the event API.
 
diff --git a/iocp-internal.h b/iocp-internal.h
index c444cc39..eb2eae49 100644
--- a/iocp-internal.h
+++ b/iocp-internal.h
@@ -155,7 +155,7 @@ void evbuffer_commit_write(struct evbuffer *, ev_ssize_t);
 
     This interface is unstable, and will change.
  */
-struct event_iocp_port *event_iocp_port_launch(void);
+struct event_iocp_port *event_iocp_port_launch(int n_cpus);
 
 /** Associate a file descriptor with an iocp, such that overlapped IO on the
     fd will happen on one of the iocp's worker threads.
@@ -164,9 +164,10 @@ int event_iocp_port_associate(struct event_iocp_port *port, evutil_socket_t fd,
     ev_uintptr_t key);
 
 /** Tell all threads serving an iocp to stop.  Wait for up to waitMsec for all
-    the threads to finish whatever they're doing.  If all the threads are
-    done, free the port and return 0.  Otherwise, return -1.  If you get a -1
-    return value, it is safe to call this function again.
+    the threads to finish whatever they're doing.  If waitMsec is -1, wait
+    as long as required.  If all the threads are done, free the port and return
+    0. Otherwise, return -1.  If you get a -1 return value, it is safe to call
+    this function again.
 */
 int event_iocp_shutdown(struct event_iocp_port *port, long waitMsec);
 
@@ -180,7 +181,8 @@ struct event_base;
 struct event_iocp_port *event_base_get_iocp(struct event_base *base);
 
 /* FIXME document. */
-int event_base_start_iocp(struct event_base *base);
+int event_base_start_iocp(struct event_base *base, int n_cpus);
+void event_base_stop_iocp(struct event_base *base);
 
 /* FIXME document. */
 struct bufferevent *bufferevent_async_new(struct event_base *base,
diff --git a/test/bench_http.c b/test/bench_http.c
index fdcf49dd..4b2eb3cd 100644
--- a/test/bench_http.c
+++ b/test/bench_http.c
@@ -133,7 +133,7 @@ main(int argc, char **argv)
 		case 'i':
 			use_iocp = 1;
 			evthread_use_windows_threads();
-			event_base_start_iocp(base);
+			event_base_start_iocp(base, 0);
 			break;
 #endif
 		default:
diff --git a/test/regress_bufferevent.c b/test/regress_bufferevent.c
index 370eee01..de97909f 100644
--- a/test/regress_bufferevent.c
+++ b/test/regress_bufferevent.c
@@ -426,9 +426,8 @@ listen_cb(struct evconnlistener *listener, evutil_socket_t fd,
 	TT_BLATHER(("Got a request on socket %d", (int)fd ));
 	bev = bufferevent_socket_new(base, fd, bufferevent_connect_test_flags);
 	tt_assert(bev);
-	bufferevent_write(bev, s, sizeof(s));
 	bufferevent_setcb(bev, NULL, sender_writecb, sender_errorcb, NULL);
-	bufferevent_enable(bev, EV_WRITE);
+	bufferevent_write(bev, s, sizeof(s));
 end:
 	;
 }
@@ -527,13 +526,6 @@ test_bufferevent_connect(void *arg)
 	tt_want(!bufferevent_socket_connect(bev1, sa, sizeof(localhost)));
 	tt_want(!bufferevent_socket_connect(bev2, sa, sizeof(localhost)));
 
-#ifdef WIN32
-	/* FIXME this is to get IOCP to work. it shouldn't be required. */
-	{
-		struct timeval tv = {5000,0};
-		event_base_loopexit(data->base, &tv);
-	}
-#endif
 	event_base_dispatch(data->base);
 
 	tt_int_op(n_strings_read, ==, 2);
@@ -622,13 +614,6 @@ test_bufferevent_connect_fail(void *arg)
 	event_add(&close_listener_event, &one_second);
 	close_listener_event_added = 1;
 
-#ifdef WIN32
-	/* FIXME this is to get IOCP to work. it shouldn't be required. */
-	{
-		struct timeval tv = {5000,0};
-		event_base_loopexit(data->base, &tv);
-	}
-#endif
 	event_base_dispatch(data->base);
 
 	tt_int_op(test_ok, ==, 1);
diff --git a/test/regress_iocp.c b/test/regress_iocp.c
index 64e86320..920da2a7 100644
--- a/test/regress_iocp.c
+++ b/test/regress_iocp.c
@@ -29,6 +29,7 @@
 #include <event2/event.h>
 #include <event2/thread.h>
 #include <event2/buffer.h>
+#include <event2/buffer_compat.h>
 #include <event2/bufferevent.h>
 
 #include <winsock2.h>
@@ -44,6 +45,7 @@
 #undef WIN32_LEAN_AND_MEAN
 
 #include "iocp-internal.h"
+#include "evbuffer-internal.h"
 #include "evthread-internal.h"
 
 /* FIXME remove these ones */
@@ -52,6 +54,62 @@
 #include "event-internal.h"
 
 #define MAX_CALLS 16
+
+static void *count_lock = NULL, *count_cond = NULL;
+static int count = 0;
+
+static void
+count_init(void)
+{
+	EVTHREAD_ALLOC_LOCK(count_lock, 0);
+	EVTHREAD_ALLOC_COND(count_cond);
+
+	tt_assert(count_lock);
+	tt_assert(count_cond);
+
+end:
+	;
+}
+
+static void
+count_free(void)
+{
+	EVTHREAD_FREE_LOCK(count_lock, 0);
+	EVTHREAD_FREE_COND(count_cond);
+}
+
+static void
+count_incr(void)
+{
+	EVLOCK_LOCK(count_lock, 0);
+	count++;
+	EVTHREAD_COND_BROADCAST(count_cond);
+	EVLOCK_UNLOCK(count_lock, 0);
+}
+
+static int
+count_wait_for(int i, int ms)
+{
+	struct timeval tv;
+	DWORD elapsed;
+	int rv = -1;
+
+	EVLOCK_LOCK(count_lock, 0);
+	while (ms > 0 && count != i) {
+		tv.tv_sec = 0;
+		tv.tv_usec = ms * 1000;
+		elapsed = GetTickCount();
+		EVTHREAD_COND_WAIT_TIMED(count_cond, count_lock, &tv);
+		elapsed = GetTickCount() - elapsed;
+		ms -= elapsed;
+	}
+	if (count == i)
+		rv = 0;
+	EVLOCK_UNLOCK(count_lock, 0);
+
+	return rv;
+}
+
 struct dummy_overlapped {
 	struct event_overlapped eo;
 	void *lock;
@@ -73,6 +131,8 @@ dummy_cb(struct event_overlapped *o, uintptr_t key, ev_ssize_t n, int ok)
 	}
 	d_o->call_count++;
 	EVLOCK_UNLOCK(d_o->lock, 0);
+
+	count_incr();
 }
 
 static int
@@ -100,6 +160,7 @@ test_iocp_port(void *ptr)
 	memset(&o1, 0, sizeof(o1));
 	memset(&o2, 0, sizeof(o2));
 
+	count_init();
 	EVTHREAD_ALLOC_LOCK(o1.lock, EVTHREAD_LOCKTYPE_RECURSIVE);
 	EVTHREAD_ALLOC_LOCK(o2.lock, EVTHREAD_LOCKTYPE_RECURSIVE);
 
@@ -109,7 +170,7 @@ test_iocp_port(void *ptr)
 	event_overlapped_init(&o1.eo, dummy_cb);
 	event_overlapped_init(&o2.eo, dummy_cb);
 
-	port = event_iocp_port_launch();
+	port = event_iocp_port_launch(0);
 	tt_assert(port);
 
 	tt_assert(!event_iocp_activate_overlapped(port, &o1.eo, 10, 100));
@@ -124,10 +185,7 @@ test_iocp_port(void *ptr)
 	tt_assert(!event_iocp_activate_overlapped(port, &o1.eo, 13, 103));
 	tt_assert(!event_iocp_activate_overlapped(port, &o2.eo, 23, 203));
 
-#ifdef WIN32
-	/* FIXME Be smarter. */
-	Sleep(1000);
-#endif
+	tt_int_op(count_wait_for(8, 2000), ==, 0);
 
 	tt_want(!event_iocp_shutdown(port, 2000));
 
@@ -145,8 +203,9 @@ test_iocp_port(void *ptr)
 	tt_want(pair_is_in(&o2, 23, 203));
 
 end:
-	/* FIXME free the locks. */
-	;
+	EVTHREAD_FREE_LOCK(o1.lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+	EVTHREAD_FREE_LOCK(o2.lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+	count_free();
 }
 
 static struct evbuffer *rbuf = NULL, *wbuf = NULL;
@@ -157,6 +216,7 @@ read_complete(struct event_overlapped *eo, uintptr_t key,
 {
 	tt_assert(ok);
 	evbuffer_commit_read(rbuf, nbytes);
+	count_incr();
 end:
 	;
 }
@@ -167,6 +227,7 @@ write_complete(struct event_overlapped *eo, uintptr_t key,
 {
 	tt_assert(ok);
 	evbuffer_commit_write(wbuf, nbytes);
+	count_incr();
 end:
 	;
 }
@@ -177,9 +238,12 @@ test_iocp_evbuffer(void *ptr)
 	struct event_overlapped rol, wol;
 	struct basic_test_data *data = ptr;
 	struct event_iocp_port *port = NULL;
+	struct evbuffer *buf;
+	struct evbuffer_chain *chain;
 	char junk[1024];
 	int i;
 
+	count_init();
 	event_overlapped_init(&rol, read_complete);
 	event_overlapped_init(&wol, write_complete);
 
@@ -191,7 +255,7 @@ test_iocp_evbuffer(void *ptr)
 	evbuffer_enable_locking(rbuf, NULL);
 	evbuffer_enable_locking(wbuf, NULL);
 
-	port = event_iocp_port_launch();
+	port = event_iocp_port_launch(0);
 	tt_assert(port);
 	tt_assert(rbuf);
 	tt_assert(wbuf);
@@ -202,14 +266,18 @@ test_iocp_evbuffer(void *ptr)
 	for (i=0;i<10;++i)
 		evbuffer_add(wbuf, junk, sizeof(junk));
 
+	buf = evbuffer_new();
+	tt_assert(buf != NULL);
+	evbuffer_add(rbuf, junk, sizeof(junk));
+	tt_assert(!evbuffer_launch_read(rbuf, 2048, &rol));
+	evbuffer_add_buffer(buf, rbuf);
+	tt_int_op(evbuffer_get_length(buf), ==, sizeof(junk));
+	for (chain = buf->first; chain; chain = chain->next)
+		tt_int_op(chain->flags & EVBUFFER_MEM_PINNED_ANY, ==, 0);
 	tt_assert(!evbuffer_get_length(rbuf));
 	tt_assert(!evbuffer_launch_write(wbuf, 512, &wol));
-	tt_assert(!evbuffer_launch_read(rbuf, 2048, &rol));
 
-#ifdef WIN32
-	/* FIXME this is stupid. */
-	Sleep(1000);
-#endif
+	tt_int_op(count_wait_for(2, 2000), ==, 0);
 
 	tt_int_op(evbuffer_get_length(rbuf),==,512);
 
@@ -217,8 +285,20 @@ test_iocp_evbuffer(void *ptr)
 
 	tt_want(!event_iocp_shutdown(port, 2000));
 end:
+	count_free();
 	evbuffer_free(rbuf);
 	evbuffer_free(wbuf);
+	evbuffer_free(buf);
+}
+
+static int got_readcb = 0;
+
+static void
+async_readcb(struct bufferevent *bev, void *arg)
+{
+	/* Disabling read should cause the loop to quit */
+	bufferevent_disable(bev, EV_READ);
+	got_readcb++;
 }
 
 static void
@@ -229,9 +309,8 @@ test_iocp_bufferevent_async(void *ptr)
 	struct bufferevent *bea1=NULL, *bea2=NULL;
 	char buf[128];
 	size_t n;
-	struct timeval one_sec = {1,0};
 
-	event_base_start_iocp(data->base);
+	event_base_start_iocp(data->base, 0);
 	port = event_base_get_iocp(data->base);
 	tt_assert(port);
 
@@ -242,27 +321,27 @@ test_iocp_bufferevent_async(void *ptr)
 	tt_assert(bea1);
 	tt_assert(bea2);
 
-	/*FIXME set some callbacks */
+	bufferevent_setcb(bea2, async_readcb, NULL, NULL, NULL);
 	bufferevent_enable(bea1, EV_WRITE);
 	bufferevent_enable(bea2, EV_READ);
 
 	bufferevent_write(bea1, "Hello world", strlen("Hello world")+1);
 
-	event_base_loopexit(data->base, &one_sec);
 	event_base_dispatch(data->base);
 
+	tt_int_op(got_readcb, ==, 1);
 	n = bufferevent_read(bea2, buf, sizeof(buf)-1);
 	buf[n]='\0';
 	tt_str_op(buf, ==, "Hello world");
 
-	tt_want(!event_iocp_shutdown(port, 2000));
 end:
-	/* FIXME: free stuff. */;
+	bufferevent_free(bea1);
+	bufferevent_free(bea2);
 }
 
 
 struct testcase_t iocp_testcases[] = {
-	{ "port", test_iocp_port, TT_FORK|TT_NEED_THREADS, NULL, NULL },
+	{ "port", test_iocp_port, TT_FORK|TT_NEED_THREADS, &basic_setup, NULL },
 	{ "evbuffer", test_iocp_evbuffer,
 	  TT_FORK|TT_NEED_SOCKETPAIR|TT_NEED_THREADS,
 	  &basic_setup, NULL },
diff --git a/test/regress_main.c b/test/regress_main.c
index 7d18938b..3732f098 100644
--- a/test/regress_main.c
+++ b/test/regress_main.c
@@ -209,7 +209,7 @@ basic_test_setup(const struct testcase_t *testcase)
 			exit(1);
 	}
 	if (testcase->flags & TT_ENABLE_IOCP_FLAG) {
-		if (event_base_start_iocp(base)<0) {
+		if (event_base_start_iocp(base, 0)<0) {
 			event_base_free(base);
 			return (void*)TT_SKIP;
 		}
diff --git a/test/regress_thread.c b/test/regress_thread.c
index 88b0e167..7401f362 100644
--- a/test/regress_thread.c
+++ b/test/regress_thread.c
@@ -33,6 +33,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#ifndef WIN32
+#include <unistd.h>
+#endif
 
 #ifdef _EVENT_HAVE_PTHREADS
 #include <pthread.h>
@@ -52,6 +55,7 @@
 #include "event2/thread.h"
 #include "evthread-internal.h"
 #include "event-internal.h"
+#include "defer-internal.h"
 #include "regress.h"
 #include "tinytest_macros.h"
 
@@ -386,6 +390,95 @@ end:
 	;
 }
 
+#define CB_COUNT 128
+#define QUEUE_THREAD_COUNT 8
+
+#ifdef WIN32
+#define SLEEP_MS(ms) Sleep(ms)
+#else
+#define SLEEP_MS(ms) usleep((ms) * 1000)
+#endif
+
+struct deferred_test_data {
+	struct deferred_cb cbs[CB_COUNT];
+	struct deferred_cb_queue *queue;
+};
+
+static time_t timer_start = 0;
+static time_t timer_end = 0;
+static unsigned callback_count = 0;
+static THREAD_T load_threads[QUEUE_THREAD_COUNT];
+static struct deferred_test_data deferred_data[QUEUE_THREAD_COUNT];
+
+static void
+deferred_callback(struct deferred_cb *cb, void *arg)
+{
+	SLEEP_MS(1);
+	callback_count += 1;
+}
+
+static THREAD_FN
+load_deferred_queue(void *arg)
+{
+	struct deferred_test_data *data = arg;
+	size_t i;
+
+	for (i = 0; i < CB_COUNT; ++i) {
+		event_deferred_cb_init(&data->cbs[i], deferred_callback, NULL);
+		event_deferred_cb_schedule(data->queue, &data->cbs[i]);
+		SLEEP_MS(1);
+	}
+
+	THREAD_RETURN();
+}
+
+static void
+timer_callback(evutil_socket_t fd, short what, void *arg)
+{
+	timer_end = time(NULL);
+}
+
+static void
+start_threads_callback(evutil_socket_t fd, short what, void *arg)
+{
+	int i;
+
+	for (i = 0; i < QUEUE_THREAD_COUNT; ++i) {
+		THREAD_START(load_threads[i], load_deferred_queue,
+				&deferred_data[i]);
+	}
+}
+
+static void
+thread_deferred_cb_skew(void *arg)
+{
+	struct basic_test_data *data = arg;
+	struct timeval tv_timer = {4, 0};
+	struct event event_threads;
+	struct deferred_cb_queue *queue;
+	int i;
+
+	queue = event_base_get_deferred_cb_queue(data->base);
+	tt_assert(queue);
+
+	for (i = 0; i < QUEUE_THREAD_COUNT; ++i)
+		deferred_data[i].queue = queue;
+
+	timer_start = time(NULL);
+	event_base_once(data->base, -1, EV_TIMEOUT, timer_callback, NULL,
+			&tv_timer);
+	event_base_once(data->base, -1, EV_TIMEOUT, start_threads_callback,
+			NULL, NULL);
+	event_base_dispatch(data->base);
+
+	TT_BLATHER(("callback count, %u", callback_count));
+	tt_int_op(timer_end - timer_start, ==, 4);
+
+end:
+	for (i = 0; i < QUEUE_THREAD_COUNT; ++i)
+		THREAD_JOIN(load_threads[i]);
+}
+
 #define TEST(name)							\
 	{ #name, thread_##name, TT_FORK|TT_NEED_THREADS|TT_NEED_BASE,	\
 	  &basic_setup, NULL }
@@ -398,6 +491,7 @@ struct testcase_t thread_testcases[] = {
 	  &basic_setup, (char*)"forking" },
 #endif
 	TEST(conditions_simple),
+	TEST(deferred_cb_skew),
 	END_OF_TESTCASES
 };