[ofiwg] mapping adapter memory

[Christoph Lameter]

The VFIO capabilties of Linux allow the mapping of an adapter VF into user
space. Intel has an implementation of a library that uses VFIO to control
adapters and there is also a Mellanox userspace driver that can use VFIO.
There is already a standard for this.

For the generic abstraction of a NIC in user space see http://dpdk.org


On Wed, Sep 24, 2014 at 5:41 PM, Reese Faucette (rfaucett) <
rfaucett at cisco.com> wrote:

>  Many adapters allow mapping memory regions on the adapter into
> user-space for efficient PIO-based sending and receiving.  This is often a
> big performance win and seems worthwhile finding an efficient abstract
> for.  Has this been discussed at all?
>
>
>
> The approach of “let the provider find the best way to use the hardware
> resources and hide that from the user” will not always work in this case,
> as the constraints on adapter-mapped memory may prevent it from being a
> general solution.  For example, it may be a limited resource, and so not
> every EP will have access to it, and those that do may have restrictions
> that other EPs do not have (e.g. fewer send credits available, smaller MTU).
>
>
>
> Any thoughts on whether this is worth trying to come up with some
> abstraction for?  From Cisco’s point of view, it definitely is – it
> requires some level of EP differentiation such that it cannot be totally
> transparent to the app, but it can drop latency by 20%, a worthwhile goal
> for us.
>
>
>
> As another example, the new Solarflare NICs are pushing this as a feature
> also:
>
>
> https://support.solarflare.com/index.php?option=com_cognidox&file=SF-111142-TC-1_Introduction_to_SFC91xx_ASIC_Family.pdf&task=download&format=raw&Itemid=17
>
>
>
> See section on “PIO and Templates” – it’s not just us J
>
>
>
> -reese
>
>
>
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