From 54435a73b848ee16d78dfca1817f7f33fe6f82f0 Mon Sep 17 00:00:00 2001
From: Arvid Norberg <arvid@libtorrent.org>
Date: Sun, 20 Mar 2011 07:43:57 +0000
Subject: [PATCH] optimization for kick-starting sockets to download again
 after having been blocked by the disk

---
 src/session_impl.cpp | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/session_impl.cpp b/src/session_impl.cpp
index 026a4a502..4473ae1fa 100644
--- a/src/session_impl.cpp
+++ b/src/session_impl.cpp
@@ -2457,12 +2457,20 @@ namespace aux {
 			conns.push_back(p);
 		}
 
-		for (std::vector<peer_connection*>::iterator i = conns.begin()
-			, end(conns.end()); i != end; ++i)
+		// pick a random peer to start with, to evenly distribute
+		// the disk bandwidth
+		std::vector<peer_connection*>::iterator peer = conns.begin() + (rand() % conns.size());
+		for (int i = 0; i < conns.size(); ++i)
 		{
+			// if we can't write to disk anymore, no need
+			// to keep iterating
+			if (!can_write_to_disk()) break;
+
 			// setup_receive() may disconnect the connection
 			// and clear it out from the m_connections list
-			(*i)->on_disk();
+			(*peer)->on_disk();
+			++peer;
+			if (peer == conns.end()) peer = conns.begin();
 		}
 	}