On 2017年08月30日 11:11, Willem de Bruijn wrote:
On Tue, Aug 29, 2017 at 9:45 PM, Jason Wang <jasowang@xxxxxxxxxx> wrote:
On 2017年08月30日 03:35, Willem de Bruijn wrote:
On Fri, Aug 25, 2017 at 9:03 PM, Willem de Bruijn
<willemdebruijn.kernel@xxxxxxxxx> wrote:
On Fri, Aug 25, 2017 at 7:32 PM, Michael S. Tsirkin <mst@xxxxxxxxxx>
wrote:
On Fri, Aug 25, 2017 at 06:44:36PM -0400, Willem de Bruijn wrote:
[...]
Incomplete results at this stage, but I do see this correlation between
flows. It occurs even while not running out of zerocopy descriptors,
which I cannot yet explain.
Running two threads in a guest, each with a udp socket, each
sending up to 100 datagrams, or until EAGAIN, every msec.
Sender A sends 1B datagrams.
Sender B sends VHOST_GOODCOPY_LEN, which is enough
to trigger zcopy_used in vhost net.
A local receive process on the host receives both flows. To avoid
a deep copy when looping the packet onto the receive path,
changed skb_orphan_frags_rx to always return false (gross hack).
The flow with the larger packets is redirected through netem on ifb0:
modprobe ifb
ip link set dev ifb0 up
tc qdisc add dev ifb0 root netem limit $LIMIT rate 1MBit
tc qdisc add dev tap0 ingress
tc filter add dev tap0 parent ffff: protocol ip \
u32 match ip dport 8000 0xffff \
action mirred egress redirect dev ifb0
For 10 second run, packet count with various ifb0 queue lengths $LIMIT:
no filter
rx.A: ~840,000
rx.B: ~840,000
Just to make sure I understand the case here. What did rx.B mean here? I
thought all traffic sent by Sender B has been redirected to ifb0?
It has been, but the packet still arrives at the destination socket.
IFB is a special virtual device that applies traffic shaping and
then reinjects it back at the point it was intercept by mirred.
rx.B is indeed arrival rate at the receiver, similar to rx.A.
I see, then ifb looks pretty fit to the test.
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