kernel-fxtec-pro1x/net/core
Krishna Kumar bbd8a0d3a3 net: Avoid enqueuing skb for default qdiscs
dev_queue_xmit enqueue's a skb and calls qdisc_run which
dequeue's the skb and xmits it. In most cases, the skb that
is enqueue'd is the same one that is dequeue'd (unless the
queue gets stopped or multiple cpu's write to the same queue
and ends in a race with qdisc_run). For default qdiscs, we
can remove the redundant enqueue/dequeue and simply xmit the
skb since the default qdisc is work-conserving.

The patch uses a new flag - TCQ_F_CAN_BYPASS to identify the
default fast queue. The controversial part of the patch is
incrementing qlen when a skb is requeued - this is to avoid
checks like the second line below:

+  } else if ((q->flags & TCQ_F_CAN_BYPASS) && !qdisc_qlen(q) &&
>>         !q->gso_skb &&
+          !test_and_set_bit(__QDISC_STATE_RUNNING, &q->state)) {

Results of a 2 hour testing for multiple netperf sessions (1,
2, 4, 8, 12 sessions on a 4 cpu system-X). The BW numbers are
aggregate Mb/s across iterations tested with this version on
System-X boxes with Chelsio 10gbps cards:

----------------------------------
Size |  ORG BW          NEW BW   |
----------------------------------
128K |  156964          159381   |
256K |  158650          162042   |
----------------------------------

Changes from ver1:

1. Move sch_direct_xmit declaration from sch_generic.h to
   pkt_sched.h
2. Update qdisc basic statistics for direct xmit path.
3. Set qlen to zero in qdisc_reset.
4. Changed some function names to more meaningful ones.

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-08-06 20:10:18 -07:00
..
datagram.c net: adding memory barrier to the poll and receive callbacks 2009-07-09 17:06:57 -07:00
dev.c net: Avoid enqueuing skb for default qdiscs 2009-08-06 20:10:18 -07:00
dev_mcast.c
drop_monitor.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6 2009-06-15 03:02:23 -07:00
dst.c
ethtool.c net: ethtool_op_get_rx_csum() should be public and exported 2009-07-27 11:35:31 -07:00
fib_rules.c net: Remove unused parameter from fill method in fib_rules_ops. 2009-05-20 17:26:23 -07:00
filter.c
flow.c
gen_estimator.c pkt_sched: gen_estimator: Fix signed integers right-shifts. 2009-05-25 22:47:01 -07:00
gen_stats.c
iovec.c net: Fix memcpy_toiovecend() to use the right offset 2009-06-08 00:25:39 -07:00
kmap_skb.h
link_watch.c
Makefile Network Drop Monitor: Adding Build changes to enable drop monitor 2009-03-13 12:09:29 -07:00
neighbour.c neigh: Convert garbage collection from softirq to workqueue 2009-08-02 18:35:16 -07:00
net-sysfs.c net: mark read-only arrays as const 2009-08-05 10:42:58 -07:00
net-sysfs.h
net-traces.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6 2009-06-15 03:02:23 -07:00
net_namespace.c net: move and export get_net_ns_by_pid 2009-07-12 14:03:28 -07:00
netevent.c
netpoll.c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 2009-07-09 20:18:24 -07:00
pktgen.c net pkgen.c:fix no need for check 2009-06-08 00:40:35 -07:00
request_sock.c
rtnetlink.c net: move and export get_net_ns_by_pid 2009-07-12 14:03:28 -07:00
scm.c
skb_dma_map.c net: skb_shared_info optimization 2009-06-08 00:21:48 -07:00
skbuff.c net: remove unused skb->do_not_encrypt 2009-07-24 15:05:31 -04:00
sock.c net: implement a SO_DOMAIN getsockoption 2009-08-05 13:02:57 -07:00
stream.c tcp: tcp_prequeue() can use keyed wakeups 2009-05-17 20:44:43 -07:00
sysctl_net_core.c sysctl: fix sparse warning: Should it be static? 2009-02-26 23:13:34 -08:00
user_dma.c net/core/user_dma.c: Use frag list abstraction interfaces. 2009-06-09 00:19:10 -07:00
utils.c net: core: remove unneeded include in net/core/utils.c. 2009-03-26 01:11:48 -07:00