[Beowulf] onload vs offload

Douglas Eadline deadline at eadline.org
Sun Sep 25 17:50:32 PDT 2016


Mark,

I just wrote a white paper about this for InsideHPC and Mellanox.
I did not do any benchmarking and relied on data
from Mellano ( and the focus was the co-design concept)

You can download the white paper (probably pay with your email address)
here:
http://insidehpc.com/white-paper/insidehpc-guide-to-co-design-architecture/

Or the various sections of the paper are printed openly on the
InsideHPC site. Just search "Eadline" on InsideHPC and it will
give a list of all the articles.

Two things I find interesting are 1) the Mellanox offload
into the fabric and the trends in processor clock rate.
Faster clock rates are better for on-loading, but
as more cores are crammed onto processors the clock rates
are actually dropping, if you stay with low core counts
you can get faster cores of course.

--
Doug

> I was reviewing some rather fetid marketing collateral
> about this topic, and finding mostly stuff from 2010ish.
> A lot has changed since then: onboard PCIe, CPU speed,
> inter-socket bus, NUMA sensitivity of the kernel, lots
> more cores, mem BW, presumably smarter applications, etc.
>
> Does anyone have comments on recent generations of onload
> vs offload interconnect performance?  Please don't respond
> unless it's recent and fully quantified (HW config, how
> measured, etc).
>
> I'd also be interested to hear from MPI/app people about how useful
> offload really is (how often can real apps leverage RDMA ops,
> or the simple sorts of collectives that are offloadable?)
>
> As keeper of probably the oldest living Quadrics system, I appreciate
> the appeal of offload.  OTOH, there's no question that onloading puts
> a lot of performance potential into the CPU-designer's hands...
>
> thanks, mark hahn.
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--
Doug

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