ARM network trouble after recent mbuf changes

[Warner Losh]

On Aug 26, 2013, at 11:53 PM, Hans Petter Selasky wrote:

> On 08/27/13 00:38, Michael Tuexen wrote:
>> I did some tests with a small program. Having in struct pkthdr 64 bit entities
>> results in a 64 bit alignment when used in struct mbuf. Using __packed
>> for struct mbuf, removes the padding.
> 
> 
> Hi,
> 
> Maybe you could use __aligned(8) instead, and account for the extra padding on all platforms? Packed has other disadvantages on ARM platforms when accessing the structures, like that non-aligned access is possible, and that it is sometimes slower than aligned access.

Yes, __packed is generally a really bad idea for in-memory, performance critical structures. In this case, __aligned(8) I don't think would have much of an effect since the problem is a mismatch between MLEN and its actual length (shame on whoever didn't put a compile time assert in there)....

Warner