Re: [BUG,REGRESSION?] 3.11.6+,3.12: GbE iface rate drops to few KB/s

Hi,

Willy Tarreau [off-list ref] writes:

first, thanks for all these tests.

On Wed, Nov 20, 2013 at 12:53:43AM +0100, Arnaud Ebalard wrote:
(...)

quoted

In the end, here are the conclusions *I* draw from this test session,
do not hesitate to correct me:

 - Eric, it seems something changed in linus tree betwen the beginning
   of the thread and now, which somehow reduces the effect of the
   regression we were seen: I never got back the 256KB/s.
 - You revert patch still improves the perf a lot
 - It seems reducing MVNETA_TX_DONE_TIMER_PERIOD does not help
 - w/ your revert patch, I can confirm that mvneta driver is capable of
   doing line rate w/ proper tweak of TCP send window (256KB instead of
   4M)
 - It seems I will I have to spend some time on the SATA issues I
   previously thought were an artefact of not cleaning my tree during a
   debug session [1], i.e. there is IMHO an issue.

Could you please try Eric's patch that was just merged into Linus' tree
if it was not yet in the kernel you tried :

  98e09386c0e  tcp: tsq: restore minimal amount of queueing

I have it in my quilt set.

For me it restored the original performance (I saturate the Gbps with
about 7 concurrent streams).

Further, I wrote the small patch below for mvneta. I'm not sure it's
smp-safe but it's a PoC. In mvneta_poll() which currently is only called
upon Rx interrupt, it tries to flush all possible remaining Tx descriptors
if any. That significantly improved my transfer rate, now I easily achieve
1 Gbps using a single TCP stream on the mirabox. Not tried on the AX3 yet.

It also increased the overall connection rate by 10% on empty HTTP responses
(small packets), very likely by reducing the dead time between some segments!

You'll probably want to give it a try, so here it comes.

hehe, I was falling short of patches to test tonight ;-) I will give it
a try now.

Cheers,

a+