Merge branch 'tcp-improving-RACK-cpu-performance'

Yuchung Cheng says:

====================
tcp: improving RACK cpu performance

This patch set improves the CPU consumption of the RACK TCP loss
recovery algorithm, in particular for high-speed networks. Currently,
for every ACK in recovery RACK can potentially iterate over all sent
packets in the write queue. On large BDP networks with non-trivial
losses the RACK write queue walk CPU usage becomes unreasonably high.

This patch introduces a new queue in TCP that keeps only skbs sent and
not yet (s)acked or marked lost, in time order instead of sequence
order.  With that, RACK can examine this time-sorted list and only
check packets that were sent recently, within the reordering window,
per ACK. This is the fastest way without any write queue walks. The
number of skbs examined per ACK is reduced by orders of magnitude.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 4aa40ef02d32..1d2c44e09e31 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -191,6 +191,7 @@ struct tcp_sock {
 	u32	tsoffset;	/* timestamp offset */
 
 	struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
+	struct list_head tsorted_sent_queue; /* time-sorted sent but un-SACKed skbs */
 
 	u32	snd_wl1;	/* Sequence for window update		*/
 	u32	snd_wnd;	/* The window we expect to receive	*/