linux_dsm_epyc7002/include
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
..
acpi Merge branch 'bjorn-notify' into release 2009-06-24 01:22:20 -04:00
asm-generic net: implement a SO_DOMAIN getsockoption 2009-08-05 13:02:57 -07:00
crypto
drm drm: Fix shifts which were miscalculated when converting from bitfields. 2009-06-24 16:11:04 +10:00
keys
linux rfkill: add the GPS radio type 2009-08-04 16:44:23 -04:00
math-emu
media V4L/DVB (11901): v4l2: Create helper function for bounding and aligning images 2009-06-23 03:21:18 -03:00
mtd
net net: Avoid enqueuing skb for default qdiscs 2009-08-06 20:10:18 -07:00
pcmcia
rdma
rxrpc
scsi sd, sr: fix Driver 'sd' needs updating message 2009-06-21 12:01:27 -05:00
sound
trace ext4: convert instrumentation from markers to tracepoints 2009-06-17 11:48:11 -04:00
video fbdev: s1d13xxxfb: add accelerated bitblt functions 2009-06-16 19:48:00 -07:00
xen
Kbuild [SCSI] FC Pass Thru support 2009-06-12 14:20:05 -05:00