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SubjectRe: [PATCH net-next] net: stmmac: add BQL support
On Sun, Dec 28, 2014 at 1:48 PM, Beniamino Galvani <> wrote:
> On Sun, Dec 28, 2014 at 08:25:40AM -0800, Dave Taht wrote:
>> On Sun, Dec 28, 2014 at 6:57 AM, Beniamino Galvani <> wrote:
>> > Add support for Byte Queue Limits to the STMicro MAC driver.
>> Thank you!
>> > Tested on a Amlogic S805 Cortex-A5 board, where the use of BQL
>> > slightly decreases the ping latency from ~10ms to ~3ms when the
>> > 100Mbps link is saturated by TCP streams. No difference is
>> > observed at 1Gbps.
>> I see the plural. With TSQ in place it is hard (without something like
>> the rrul test driving multiple streams) to drive a driver to
>> saturation with small numbers of flows. This was with pfifo_fast, not
>> sch_fq, at 100mbit?
> Hi Dave,
> yes, this was with pfifo_fast and I used 4 iperf TCP streams. The total
> throughput didn't seem to increase adding more streams.

>> Can this board actually drive a full gigabit in the first place? Until
>> now most of the low end arm boards I have seen only came with
>> a 100mbit mac, and the gig ones lacking offloads seemed to peak
>> out at about 600mbit.
> I measured a throughput of 650mbit in rx and 600mbit in tx.

You might want to try the rrul test which tests both directions and
latency at the same time.

In my case I have been trying to find a low-cost chip that could do soft
rate limiting (htb) + fq_codel at up to 300mbit/sec, as that is about
the peak speed
we will be getting from cable modems, and these are horribly overbuffered,
at these speeds too, with 1.2sec of bidirectional latency observed at

I'm open to crazy ideas like trying to find a use for the gpu, etc, to
get there.

>> Under my christmas tree landed a quad core A5 (odroid-c1), also an
>> xgene and zedboard - both of the latter are a-needing BQL,
>> and I haven't booted the udroid yet. Hopefully it is the
>> same driver you just improved.
> I'm using the odroid-c1 too, with this tree based on the recent
> Amlogic mainline work:

Oh, cool, thx!

> Unfortunately at the moment the support for the board is very basic
> (for example, SMP is not working yet) but it's enough to do some NIC
> tests.

Good to know. Have you looked at xmit_more yet?

> Beniamino

Dave Täht

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