[dpdk-dev] 答复: [PATCH] Add user defined tag calculation callback tolibrte_distributor.

[Qinglai Xiao <jigsaw@gmail.com>]

Hi Bruce,

There is a subtle case in which tag values are 2 and 3, respectively. Then these two tags cannot be distinguished. There should be a better way so as to handle this situation.

thx &
rgds
-qinglai

-----原始邮件-----
发件人: "Thomas Monjalon" <thomas.monjalon@6wind.com>
发送时间: ‎2014/‎11/‎6 12:36
收件人: "Bruce Richardson" <bruce.richardson@intel.com>
抄送: "dev@dpdk.org" <dev@dpdk.org>; "jigsaw" <jigsaw@gmail.com>
主题: Re: [dpdk-dev] [PATCH] Add user defined tag calculation callback tolibrte_distributor.

2014-11-06 09:22, Bruce Richardson:
> On Wed, Nov 05, 2014 at 07:24:13PM +0200, jigsaw wrote:
> > http://dpdk.org/browse/dpdk/tree/lib/librte_distributor/rte_distributor.c#n285
> > 
> >         new_tag = (next_mb->hash.rss | 1);
> > 
> > Why the logical OR is needed?
> 
> That's needed to ensure that we never track a tag with an actual value of zero.
> We instead always force the low bit to be 1, so that we can use zero as an
> "empty" value.

Bruce, could you check how this code may be better commented please?
This discussion shows that the distributor library probably needs more
explanations in the code or doxygen.

Thanks
-- 
Thomas