netdev - Re: [v1] net_sched: act_police: add 2 new attributes to support police 64bit rate and peakrate

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Date:   Thu, 29 Aug 2019 19:58:57 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     "David Z. Dai" <zdai@...ux.vnet.ibm.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, zdai@...ibm.com
Subject: Re: [v1] net_sched: act_police: add 2 new attributes to support police 64bit rate and peakrate

"David Z. Dai" <zdai@...ux.vnet.ibm.com> writes:

> 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@...ux.vnet.ibm.com>
>> > Signed-off-by: David Dai <zdai@...ux.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?

Just put the new attributes *after* PAD instead of before :)

-Toke