This patch was previously submitted as RFC. Submitting this as
non-RFC now that the tc/mqprio changes are accepted in net-next.
Adds new mqprio options for 'mode' and 'shaper'. The mode
option can take values for offload modes such as 'dcb' (default),
'channel' with the 'hw' option set to 1. The new 'channel' mode
supports offloading TCs and other queue configurations. The
'shaper' option is to support HW shapers ('dcb' default) and
takes the value 'bw_rlimit' for bandwidth rate limiting. The
parameters to the bw_rlimit shaper are minimum and maximum
bandwidth rates. New HW shapers in future can be supported
through the shaper attribute.
# tc qdisc add dev eth0 root mqprio num_tc 2 map 0 0 0 0 1 1 1 1\
queues 4@0 4@4 hw 1 mode channel shaper bw_rlimit\
min_rate 1Gbit 2Gbit max_rate 4Gbit 5Gbit
# tc qdisc show dev eth0
qdisc mqprio 804a: root tc 2 map 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0
queues:(0:3) (4:7)
mode:channel
shaper:bw_rlimit min_rate:1Gbit 2Gbit max_rate:4Gbit 5Gbit
v2: Avoid buffer overrun and minor cleanup.
Signed-off-by: Amritha Nambiar <amritha.nambiar@intel.com>
Kernel code and interface.
--------------------------
* Compile time switches
There is only one, but very important, compile time switch.
It is not settable by "make config", but should be selected
manually and after a bit of thinking in <include/net/pkt_sched.h>
PSCHED_CLOCK_SOURCE can take three values:
PSCHED_GETTIMEOFDAY
PSCHED_JIFFIES
PSCHED_CPU
PSCHED_GETTIMEOFDAY
Default setting is the most conservative PSCHED_GETTIMEOFDAY.
It is very slow both because of weird slowness of do_gettimeofday()
and because it forces code to use unnatural "timeval" format,
where microseconds and seconds fields are separate.
Besides that, it will misbehave, when delays exceed 2 seconds
(f.e. very slow links or classes bounded to small slice of bandwidth)
To resume: as only you will get it working, select correct clock
source and forget about PSCHED_GETTIMEOFDAY forever.
PSCHED_JIFFIES
Clock is derived from jiffies. On architectures with HZ=100
granularity of this clock is not enough to make reasonable
bindings to real time. However, taking into account Linux
architecture problems, which force us to use artificial
integrated clock in any case, this switch is not so bad
for schduling even on high speed networks, though policing
is not reliable.
PSCHED_CPU
It is available only for alpha and pentiums with correct
CPU timestamp. It is the fastest way, use it when it is available,
but remember: not all pentiums have this facility, and
a lot of them have clock, broken by APM etc. etc.
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