transfer: avoid polling socket every transfer loop

Improve download performance, minimal effort.

Do not poll the socket for pending data every transfer loop iteration.
This gives 10-20% performance gains on large HTTP/1.1 downloads (on my
machine).

Closes #14098

diff --git a/lib/transfer.c b/lib/transfer.c
index 4051f6743c784c8507efcf247b5d27a26417f2c8..476f9c002e190e9bfbf22a972e5c3e190344f2ed 100644 (file)
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -336,7 +336,7 @@ static CURLcode readwrite_data(struct Curl_easy *data,
     if((k->keepon & KEEP_RECV_PAUSE) || !(k->keepon & KEEP_RECV))
       break;
 
-  } while(maxloops-- && data_pending(data));
+  } while(maxloops--);
 
   if((maxloops <= 0) || data_pending(data)) {
     /* did not read until EAGAIN or there is still pending data, mark as