svn commit: r257455 - head/sys/net

[Andre Oppermann]

On 31.10.2013 19:03, Luigi Rizzo wrote:
> On Thu, Oct 31, 2013 at 03:46:10PM +0000, Andre Oppermann wrote:
>> Author: andre
>> Date: Thu Oct 31 15:46:10 2013
>> New Revision: 257455
>> URL: http://svnweb.freebsd.org/changeset/base/257455
>>
>> Log:
>>    Make struct ifnet readable and comprehensible again by grouping
>>    and ordering related variables, fields and locks next to each
>>    other.  Add more comments to variables.
>
>
>>    Over time 'ifnet' has accumlated a lot of additional pointers and
>>    functionality in an unstructured way making it quite hard to read
>>    and understand while obfuscating relationships between fields and
>>    variables.
>>
>>    Quantify the structure size and how bloated it has become.
>>
>>    This is only a mechanical change in preparation for upcoming
>>    work to make ifnet opaque to drivers and to separate out the
>>    interface queuing.
>
> as you do the above I think it would make sense to replace
> all int/short/long with fixed-size fields as appropriate
> (and large enough) to make it easier to reason about things
> such as 'how many flags can i stuff into a field'.
>
> The "large enough" part refers to two things:
> - bitfields containing flags or capabilities have a tendency
>    to overflow (not just in freebsd, linux has the same)
>    requiring KBI changes. We should probably go for 64 bits
>    unless there are compelling space reasons (not for ifnet).

Gleb will handle most of that and it is going to be part of the making
ifnet opaque to drivers.

> - it is useful if certain opaque fields (flow ids, cookies...)
>    can store pointers. Once again, make them at least 64 bit helps

A number of mbuf header fields have this property now. :)

-- 
Andre