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Subject: Re: [v1] net_sched: act_police: add 2 new attributes to support
 police 64bit rate and peakrate
From:   "David Z. Dai" <zdai@linux.vnet.ibm.com>
To:     Eric Dumazet <eric.dumazet@gmail.com>
Cc:     jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us,
        davem@davemloft.net, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, zdai@us.ibm.com
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         <7a8a5024-bbff-7443-71b3-9e3976af269f@gmail.com>
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Date:   Thu, 29 Aug 2019 12:36:25 -0500
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On Thu, 2019-08-29 at 10:32 +0200, Eric Dumazet wrote:
> 
> On 8/29/19 12:51 AM, David Dai wrote:
> > For high speed adapter like Mellanox CX-5 card, it can reach upto
> > 100 Gbits per second bandwidth. Currently htb already supports 64bit rate
> > in tc utility. However police action rate and peakrate are still limited
> > to 32bit value (upto 32 Gbits per second). Add 2 new attributes
> > TCA_POLICE_RATE64 and TCA_POLICE_RATE64 in kernel for 64bit support
> > so that tc utility can use them for 64bit rate and peakrate value to
> > break the 32bit limit, and still keep the backward binary compatibility.
> > 
> > Tested-by: David Dai <zdai@linux.vnet.ibm.com>
> > Signed-off-by: David Dai <zdai@linux.vnet.ibm.com>
> > ---
> >  include/uapi/linux/pkt_cls.h |    2 ++
> >  net/sched/act_police.c       |   27 +++++++++++++++++++++++----
> >  2 files changed, 25 insertions(+), 4 deletions(-)
> > 
> > diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
> > index b057aee..eb4ea4d 100644
> > --- a/include/uapi/linux/pkt_cls.h
> > +++ b/include/uapi/linux/pkt_cls.h
> > @@ -159,6 +159,8 @@ enum {
> >  	TCA_POLICE_AVRATE,
> >  	TCA_POLICE_RESULT,
> >  	TCA_POLICE_TM,
> > +	TCA_POLICE_RATE64,
> > +	TCA_POLICE_PEAKRATE64,
> >  	TCA_POLICE_PAD,
> >  	__TCA_POLICE_MAX
> >  #define TCA_POLICE_RESULT TCA_POLICE_RESULT
> 
> Never insert new attributes, as this breaks compatibility with old binaries (including
> old kernels)
Thanks for reviewing it!
My change is only contained within the police part. I am trying to
follow the same way htb and tbf support their 64 bit rate.

I tested the old tc binary with the newly patched kernel. It works fine.

I agree the newly compiled tc binary that has these 2 new attributes can
cause backward compatibility issue when running on the old kernel.

If can't insert new attribute, is there any
comment/suggestion/alternative on how to support 64bit police rate and
still keep the backward compatibility?

> Keep TCA_POLICE_PAD value the same, thanks.