On 18-01-17 06:06 PM, Jesus Sanchez-Palencia wrote:
From: Vinicius Costa Gomes <vinicius.go...@intel.com>
TBS (Time Based Scheduler) uses the information added earlier in this
series (the socket option SO_TXTIME and the new role of
sk_buff->tstamp) to schedule traffic transmission based on absolute
time.
For some workloads, just bandwidth enforcement is not enough, and
precise control of the transmission of packets is necessary.
Example:
$ tc qdisc replace dev enp2s0 parent root handle 100 mqprio num_tc 3 \
handle 100:0 ?
map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 queues 1@0 1@1 2@2 hw 0
$ tc qdisc add dev enp2s0 parent 100:1 tbs delta 60000 clockid 11 offload 1
In this example, the Qdisc will try to enable offloading (offload 1)
the control of the transmission time to the network adapter, the
time stamp in socket are in reference to the clockid '11' (CLOCK_TAI)
and packets leave the Qdisc "delta" (60000) nanoseconds before its
transmission time.
When offloading is disabled, the network adapter will ignore the
sk_buff time stamp, and so, the transmission time will be only "best
effort" from the Qdisc.
General comments:
1) iproute2: Avoid magic numbers like 1 or 11 please; "offload"
(without 1) and "TAI" will be more human friendly.
2) Experience shows that adding padding fields in the control structs
implies they will _never ever_ be used. That was not design intent
for netlink but over years shit like that has happened.
Maybe look at using a 32 bitmap? It is more "future proof".
You seem to only have 2-3 flags but it gives you opportunity
to add more changes later. If you are 100% sure youll never need
it - then maybe just move the tc_tbs_qopt::offload to the end of
of the struct.
3)It would be helpful for debugging to increment some stats other
than drop counters on enqueu/dequeue obsolete packet drop. Maybe use
overlimits for the dequeu drops (in addition)?
4) I may be misreading things - but did you need to reset the
watchdog on dequeue? It is already being kicked for every incoming packet.
cheers,
jamal
