Re: [Aoetools-discuss] vblade jumbo frame support

[Sam H. <sa...@co...>]

> First, thanks for putting all the effort into the open source AOE 
> applications. 

Thanks.  It's nice to work for a company that values providing open
source applications as a means of spreading the word about the
technology.

> Next, I am becoming a fan of aoe, and have a potential production 
> application, but as I have learned, it will require jumbo frame support on 
> vblade.
> My application requires a high read rate. 50MB/sec is an ideal spot. With 
> point to point gige, and with a HW raid running in the target, I can see 
> the bandwidth I need when I run aoe-exercise with jumbo frames. Vblade-10 
> with the aoetest patch seems to run the test just fine with jumbo frames. 
> The jumbo frame patch from the contributor was a nice try.. but fails to 
> perform.

I contributed the jumbo frame patch, but it's for vblade versions 12
and 13.  I don't think you can test vblade-10 with jumbo, unless I'm
missing something.

As the vblade's contrib/README states, the jumbo frame patch does not
perform well as the kernel will not buffer enough data to enable the
vblade to use jumbo frames with dropping many, many packets.  When
using the linux aoe initiator, there are 16 outstanding frames to the
vblade.  At 1060 (standard) per frame (1k data + header) there are no
dropped packets.  At 4132 (jumbo) per frame, the kernel buffers (iirc)
about half the packets and drops the rest.  cat /dev/etherd/err on the
initiator side to watch the retransmits.

I don't currently have the time to debug the vblade jumbo issue, so I
stuck it out there in hopes that another user would track down what's
causing the kernel to drop packets.  It'd be great if something like:

	echo 1000000 >/proc/net/socketbufferdata

...  would fix it, but it may be a constant in some header file
requiring a kernel recompile.

> So can I expect a jumbo vblade, or do I need to dive in and whack away at 
> the code?

If you can find the issue in the kernel the jumbo contrib patch should
just work.

Cheers,

Sam