client: always attempt to flush deferred buffers

When a response is very long (e.g. a large playlist > 100k songs), most of it will end up in the deferred buffers. Filling the deferred queue is very expensive currently, because a new buffer is allocated for every client_write() operation. This may lead to long delays, and the client might give up and disconnect meanwhile. This patch makes MPD attempt to flush the deferred queue as often as possible, to work around this problem. Due to the MPD 0.14 code freeze, we should not optimize the buffering code now.

client: always attempt to flush deferred buffers
d2d11d70 · Max Kellermann · d96cda95 · d2d11d70
Commit d2d11d70 authored Dec 24, 2008 by Max Kellermann
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Showing with 11 additions and 2 deletions

client.c src/client.c +11 -2

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--- a/src/client.c
+++ b/src/client.c
@@ -700,10 +700,19 @@ static void client_write_output(struct client *client)
 	if (client_is_expired(client) || !client->send_buf_used)
 		return;
-	if (!g_queue_is_empty(client->deferred_send))
+	if (!g_queue_is_empty(client->deferred_send)) {
 		client_defer_output(client, client->send_buf,
 				    client->send_buf_used);
-	else
+		/* try to flush the deferred buffers now; the current
+		   server command may take too long to finish, and
+		   meanwhile try to feed output to the client,
+		   otherwise it will time out.  One reason why
+		   deferring is slow might be that currently each
+		   client_write() allocates a new deferred buffer.
+		   This should be optimized after MPD 0.14. */
+		client_write_deferred(client);
+	} else
 		client_write_direct(client, client->send_buf,
 				    client->send_buf_used);