udp: add batching to udp_rmem_release()
authorEric Dumazet <edumazet@google.com>
Thu, 8 Dec 2016 19:41:56 +0000 (11:41 -0800)
committerDavid S. Miller <davem@davemloft.net>
Sat, 10 Dec 2016 03:12:21 +0000 (22:12 -0500)
commit6b229cf77d683f634f0edd876c6d1015402303ad
treeec877d3e324da74f7bbb179d4cd4a8db0172865c
parentc84d949057cab262b4d3110ead9a42a58c2958f7
udp: add batching to udp_rmem_release()

If udp_recvmsg() constantly releases sk_rmem_alloc
for every read packet, it gives opportunity for
producers to immediately grab spinlocks and desperatly
try adding another packet, causing false sharing.

We can add a simple heuristic to give the signal
by batches of ~25 % of the queue capacity.

This patch considerably increases performance under
flood by about 50 %, since the thread draining the queue
is no longer slowed by false sharing.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/linux/udp.h
net/ipv4/udp.c