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
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