if tr_torrentStat() is called again in the same second for a torrent, return the cached value.

libtransmission/internal.h

@@ -162,6 +162,7 @@ struct tr_torrent
 
     tr_recheck_state           recheckState;
 
+    time_t                     lastStatTime;
     tr_stat                    stats[2];
 
     tr_torrent               * next;

libtransmission/torrent.c

@@ -713,6 +713,13 @@ tr_torrentStat( tr_torrent * tor )
 {
     tr_stat * s;
     struct tr_tracker * tc;
+    const time_t now = time( NULL );
+
+    /* generating these stats is expensive --
+     * update a maximum of once per second */
+    if( tor->lastStatTime == now )
+        return &tor->stats[tor->statCur];
+    tor->lastStatTime = now;
 
     tr_torrentLock( tor );