netdev - Re: [net-next PATCH v1 08/11] net: rocker: add get flow API operation

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Date:	Tue, 06 Jan 2015 09:50:52 -0800
From:	John Fastabend <john.fastabend@...il.com>
To:	Scott Feldman <sfeldma@...il.com>
CC:	Thomas Graf <tgraf@...g.ch>,
	Jiří Pírko <jiri@...nulli.us>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	"simon.horman@...ronome.com" <simon.horman@...ronome.com>,
	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [net-next PATCH v1 08/11] net: rocker: add get flow API operation

On 01/06/2015 08:57 AM, Scott Feldman wrote:
> On Tue, Jan 6, 2015 at 6:59 AM, John Fastabend <john.fastabend@...il.com> wrote:
>> On 01/05/2015 11:40 PM, Scott Feldman wrote:
>>>
>>> On Wed, Dec 31, 2014 at 11:48 AM, John Fastabend
>>> <john.fastabend@...il.com> wrote:
>>>>
>>>> Add operations to get flows. I wouldn't mind cleaning this code
>>>> up a bit but my first attempt to do this used macros which shortered
>>>> the code up but when I was done I decided it just made the code
>>>> unreadable and unmaintainable.
>>>>
>>>> I might think about it a bit more but this implementation albeit
>>>> a bit long and repeatative is easier to understand IMO.
>>>
>>>
>>> Dang, you put a lot of work into this one.
>>>
>>> Something doesn't feel right though.  In this case, rocker driver just
>>> happened to have cached all the flow/group stuff in hash tables in
>>> software, so you don't need to query thru to the device to extract the
>>> if_flow info.  What doesn't feel right is all the work need in the
>>> driver.  For each and every driver.  get_flows needs to go above
>>> driver, somehow.
>>
>>
>> Another option is to have a software cache in the flow_table.c I
>> was trying to avoid caching as I really don't expect 'get' operations
>> to be fast path and going to hardware seems good enough for me.
>> Other than its a bit annoying to write the mapping code.
>
> Caching in flow_table.c seems best to me as drivers/devices don't need
> to be involved and the cache can server multiple users of the API.
> Are there cases where the device could get flow table entries
> installed/deleted outside the API?  For example, if the device was
> learning MAC addresses, and did automatic table insertions.  We worked
> around that case with the recent L2 swdev support by pushing learned
> MAC addrs up to bridge's FDB so software and hardware tables stay
> synced.
>

OK I guess I'm convinced. I'll go ahead and cache the flow entries in
software. I'll work this into v2.

-- 
John Fastabend         Intel Corporation
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