On Mon, 5 Dec 2022 21:44:09 +0100 Justin Iurman wrote: > > Please revert this patch. > > > > Many people use FQ qdisc, where packets are waiting for their Earliest > > Departure Time to be released. > > The IOAM queue depth is a very important value and is already used. Can you say more about the use? What signal do you derive from it? I do track qlen on Meta's servers but haven't found a strong use for it yet (I did for backlog drops but not the qlen itself). > > Also, the draft says: > > > > 5.4.2.7. queue depth > > > > The "queue depth" field is a 4-octet unsigned integer field. This > > field indicates the current length of the egress interface queue of > > the interface from where the packet is forwarded out. The queue > > depth is expressed as the current amount of memory buffers used by > > the queue (a packet could consume one or more memory buffers, > > depending on its size). > > > > 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > | queue depth | > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > > > > It is relatively clear that the egress interface is the aggregate > > egress interface, > > not a subset of the interface. > > Correct, even though the definition of an interface in RFC 9197 is quite > abstract (see the end of section 4.4.2.2: "[...] could represent a > physical interface, a virtual or logical interface, or even a queue"). > > > If you have 32 TX queues on a NIC, all of them being backlogged (line rate), > > sensing the queue length of one of the queues would give a 97% error > > on the measure. > > Why would it? Not sure I get your idea based on that example. Because it measures the length of a single queue not the device.
