[PATCH spice-gtk 07/10] channel: do not reenter the mainloop at every iteration

["Marc-André Lureau" <marcandre.lureau@xxxxxxxxx>]

From: Marc-André Lureau <marcandre.lureau@xxxxxxxxx>

The current coroutine channel_iterate() creates a GSource for the socket
reenters the mainloop waiting for IO condition. This is really heavy
usage of mainloop showing up in system time and user space
profiling (10% of CPU time spent in mainloop overhead). Instead flush
all pending input messages before switching context and reentering main
loop.
---
 gtk/spice-channel.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/gtk/spice-channel.c b/gtk/spice-channel.c
index 778a90b..9fb3b0c 100644
--- a/gtk/spice-channel.c
+++ b/gtk/spice-channel.c
@@ -2107,35 +2107,34 @@ static gboolean spice_channel_iterate(SpiceChannel *channel)
     SpiceChannelPrivate *c = channel->priv;
     GIOCondition ret;
 
-    do {
-        if (c->state == SPICE_CHANNEL_STATE_MIGRATING &&
-            !g_coroutine_condition_wait(&c->coroutine, wait_migration, channel))
-                CHANNEL_DEBUG(channel, "migration wait cancelled");
+    if (c->state == SPICE_CHANNEL_STATE_MIGRATING &&
+        !g_coroutine_condition_wait(&c->coroutine, wait_migration, channel))
+        CHANNEL_DEBUG(channel, "migration wait cancelled");
 
-        if (c->has_error) {
-            CHANNEL_DEBUG(channel, "channel has error, breaking loop");
-            return FALSE;
-        }
-
-        SPICE_CHANNEL_GET_CLASS(channel)->iterate_write(channel);
+    if (c->has_error) {
+        CHANNEL_DEBUG(channel, "channel has error, breaking loop");
+        return FALSE;
+    }
 
-        ret = g_coroutine_socket_wait(&c->coroutine, c->sock,
-            c->state != SPICE_CHANNEL_STATE_MIGRATING ? G_IO_IN : 0);
+    /* flush any pending write */
+    SPICE_CHANNEL_GET_CLASS(channel)->iterate_write(channel);
+    /* go back to main loop, wait for an event or incoming data */
+    ret = g_coroutine_socket_wait(&c->coroutine, c->sock, G_IO_IN);
 
-#ifdef WIN32
-        /* FIXME: windows gsocket is buggy, it doesn't return correct condition... */
-        ret = g_socket_condition_check(c->sock, G_IO_IN);
-#endif
-    } while (ret == 0); /* ret == 0 means no IO condition, but woken up */
+    /* treat all incoming data (block on message completion) */
+    while (!c->has_error && (ret & G_IO_IN)) {
+        if (c->state == SPICE_CHANNEL_STATE_MIGRATING)
+            break;
 
-    if (ret & G_IO_IN) {
         do
             SPICE_CHANNEL_GET_CLASS(channel)->iterate_read(channel);
 #if HAVE_SASL
+        /* flush the sasl buffer too */
         while (c->sasl_decoded != NULL);
 #else
         while (FALSE);
 #endif
+        ret = g_socket_condition_check(c->sock, G_IO_IN | G_IO_ERR | G_IO_HUP);
     }
 
     if (c->state > SPICE_CHANNEL_STATE_CONNECTING &&
-- 
1.8.3.1

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