glib: fix g_poll early timeout on windows

g_poll has a problem on Windows when using
timeouts < 10ms, in glib/gpoll.c:

/* If not, and we have a significant timeout, poll again with
 * timeout then. Note that this will return indication for only
 * one event, or only for messages. We ignore timeouts less than
 * ten milliseconds as they are mostly pointless on Windows, the
 * MsgWaitForMultipleObjectsEx() call will timeout right away
 * anyway.
 */
if (retval == 0 && (timeout == INFINITE || timeout >= 10))
  retval = poll_rest (poll_msgs, handles, nhandles, fds, nfds, timeout);

so whenever g_poll is called with timeout < 10ms it does
a quick poll instead of wait, this causes significant performance
degradation of QEMU, thus we should use WaitForMultipleObjectsEx
directly

Signed-off-by: Stanislav Vorobiov <s.vorobiov@samsung.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/include/glib-compat.h b/include/glib-compat.h
index 8d25900..1280fb2 100644
--- a/include/glib-compat.h
+++ b/include/glib-compat.h
@@ -24,7 +24,14 @@ static inline guint g_timeout_add_seconds(guint interval, GSourceFunc function,
 }
 #endif
 
-#if !GLIB_CHECK_VERSION(2, 20, 0)
+#ifdef _WIN32
+/*
+ * g_poll has a problem on Windows when using
+ * timeouts < 10ms, so use wrapper.
+ */
+#define g_poll(fds, nfds, timeout) g_poll_fixed(fds, nfds, timeout)
+gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout);
+#elif !GLIB_CHECK_VERSION(2, 20, 0)
 /*
  * Glib before 2.20.0 doesn't implement g_poll, so wrap it to compile properly
  * on older systems.