Re: [PATCH] fcoe: Reduce max_sectors to 1024

Hannes Reinecke
2014-07-09T06:40:33Z

On 07/09/2014 08:18 AM, Christoph Hellwig wrote:
> On Wed, Jul 09, 2014 at 08:16:21AM +0200, Hannes Reinecke wrote:
>> The DDP offload on ixgbe is only capable of handling requests up
>> to 1024 sectors. So we should be exposing this to avoid spurious
>> messages about 'not enough user buffers'.
>
> Shouldn't the network driver be able to communicate it's offload
> capabilities to the fcoe core? I'd be happy to take this as an iterim
> fix if there's a comment explaining it, but long-term it should be
> driver specific.
>
ixgbe can handle up to 256 sgl elements, but the maximum single I/O
size is 256 pages. This translates into 1024 sectors.

And seeing that the 'fcoe' driver is effectively tied to ixgbe ATM I
doubt it's worth investing in yet another callout here.
Intel, can you clarify on i40e? Is it FCoE capable?
If so it might be worth adding a configuration knob here.
Unless i40e has the same limitations as ixgbe ...

Cheers,

Hannes
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Dr. Hannes Reinecke zSeries & Storage
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