[Cake] tc coding comments

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Thu Nov 19 07:05:40 EST 2015



On 19/11/15 08:56, Dave Taht wrote:
> tc qdisc add dev whatever root cake bandwidth 50gbit does not work
Grins.  I was sort of looking at this yesterday.  It's a 32 bit integer
'limit' within tc.  tc works in bits per second, but what it passes to
kernel is bytes per second (>>3)  So the 32bit netlink API interface can
potentially cope with 34359738360 bits per second(2^32 -1 * 8),
unfortunately tc's get_rate() can only cope with 4294967295 (2^32 -1)
bits per second.  get_rate64() would solve that along with a 64bit
netlink api rate path.

A quick look at iproute2 master reveals netem, tbf & htb as the only
users so far of get_rate64()



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