On 3/5/19 4:06 PM, Matthew Macy wrote:
This represents a misunderstanding of how defines are used. This left
the option open to the user to enable the use of larger than page size
buffers as it does enable better performance. Over the course of a
long uptime memory can get too fragmented. However, this left it open
to the end consumer.
I'd like to see this reverted with perhaps a better name for the
define and the addition of an explanatory comment.
I'd strongly prefer that it stay removed. Since it is not hooked to an
option, no user is ever going to find it. This really should have been
a tuneable (since it is done at ring init time, rather than rx buffer
alloc time), but nobody cared enough to make it actually usable.
From brief memories of performance tuning 10G adapters 14 years ago,
the differences between page-sized and 9k jumbos were minimal even back
then (1/3 as many mbuf alloc/free, smaller chains). So I'm not
convinced that it is worth bringing back in any form.
My general feeling is that the more of this code that we can remove, the
better. Iflib is tricky enough that it is already challenging to reason
about and maintain. Removing code which is for all intents and purposes
unreachable and never tested is Good Thing.
Drew
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