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From: Michel Machado <michel@digirati.com.br>
To: "Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>,
	Kevin Traynor <ktraynor@redhat.com>,
	Ruifeng Wang <Ruifeng.Wang@arm.com>,
	Bruce Richardson <bruce.richardson@intel.com>,
	Cody Doucette <doucette@bu.edu>,
	Andre Nathan <andre@digirati.com.br>,
	Qiaobin Fu <mengxiang0811@gmail.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH 2/2] lpm: hide internal data
Date: Tue, 13 Oct 2020 13:46:27 -0400
Message-ID: <18c44f31-abc0-c0b5-c2fb-76d6166d5237@digirati.com.br> (raw)
In-Reply-To: <ecbf6a35-7901-e684-3ceb-d8a80ad7c4df@intel.com>

On 10/13/20 11:41 AM, Medvedkin, Vladimir wrote:
> Hi Michel,
> 
> Could you please describe a condition when LPM gets inconsistent? As I 
> can see if there is no free tbl8 it will return -ENOSPC.

    Consider this simple example, we need to add the following two 
prefixes with different next hops: 10.99.0.0/16, 18.99.99.128/25. If the 
LPM table is out of tbl8s, the second prefix is not added and Gatekeeper 
will make decisions in violation of the policy. The data structure of 
the LPM table is consistent, but its content inconsistent with the policy.

    We minimize the need of replacing a LPM table by allocating LPM 
tables with the double of what we need (see example here 
https://github.com/AltraMayor/gatekeeper/blob/95d1d6e8201861a0d0c698bfd06ad606674f1e07/lua/examples/policy.lua#L172-L183), 
but the code must be ready for unexpected needs that may arise in 
production.

> 
> On 13/10/2020 15:58, Michel Machado wrote:
>> Hi Kevin,
>>
>>     We do need fields max_rules and number_tbl8s of struct rte_lpm, so 
>> the removal would force us to have another patch to our local copy of 
>> DPDK. We'd rather avoid this new local patch because we wish to 
>> eventually be in sync with the stock DPDK.
>>
>>     Those fields are needed in Gatekeeper because we found a condition 
>> in an ongoing deployment in which the entries of some LPM tables may 
>> suddenly change a lot to reflect policy changes. To avoid getting into 
>> a state in which the LPM table is inconsistent because it cannot fit 
>> all the new entries, we compute the needed parameters to support the 
>> new entries, and compare with the current parameters. If the current 
>> table doesn't fit everything, we have to replace it with a new LPM table.
>>
>>     If there were a way to obtain the struct rte_lpm_config of a given 
>> LPM table, it would cleanly address our need. We have the same need in 
>> IPv6 and have a local patch to work around it (see 
>> https://github.com/cjdoucette/dpdk/commit/3eaf124a781349b8ec8cd880db26a78115cb8c8f). 
>> Thus, an IPv4 and IPv6 solution would be best.
>>
>>     PS: I've added Qiaobin Fu, another Gatekeeper maintainer, to this 
>> disscussion.
>>
>> [ ]'s
>> Michel Machado
>>
>> On 10/13/20 9:53 AM, Kevin Traynor wrote:
>>> Hi Gatekeeper maintainers (I think),
>>>
>>> fyi - there is a proposal to remove some members of a struct in DPDK LPM
>>> API that Gatekeeper is using [1]. It would be only from DPDK 20.11 but
>>> as it's an LTS I guess it would probably hit Debian in a few months.
>>>
>>> The full thread is here:
>>> http://inbox.dpdk.org/dev/20200907081518.46350-1-ruifeng.wang@arm.com/
>>>
>>> Maybe you can take a look and tell us if they are needed in Gatekeeper
>>> or you can workaround it?
>>>
>>> thanks,
>>> Kevin.
>>>
>>> [1]
>>> https://github.com/AltraMayor/gatekeeper/blob/master/gt/lua_lpm.c#L235-L248 
>>>
>>>
>>> On 09/10/2020 07:54, Ruifeng Wang wrote:
>>>>
>>>>> -----Original Message-----
>>>>> From: Kevin Traynor <ktraynor@redhat.com>
>>>>> Sent: Wednesday, September 30, 2020 4:46 PM
>>>>> To: Ruifeng Wang <Ruifeng.Wang@arm.com>; Medvedkin, Vladimir
>>>>> <vladimir.medvedkin@intel.com>; Bruce Richardson
>>>>> <bruce.richardson@intel.com>
>>>>> Cc: dev@dpdk.org; Honnappa Nagarahalli
>>>>> <Honnappa.Nagarahalli@arm.com>; nd <nd@arm.com>
>>>>> Subject: Re: [dpdk-dev] [PATCH 2/2] lpm: hide internal data
>>>>>
>>>>> On 16/09/2020 04:17, Ruifeng Wang wrote:
>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: Medvedkin, Vladimir <vladimir.medvedkin@intel.com>
>>>>>>> Sent: Wednesday, September 16, 2020 12:28 AM
>>>>>>> To: Bruce Richardson <bruce.richardson@intel.com>; Ruifeng Wang
>>>>>>> <Ruifeng.Wang@arm.com>
>>>>>>> Cc: dev@dpdk.org; Honnappa Nagarahalli
>>>>>>> <Honnappa.Nagarahalli@arm.com>; nd <nd@arm.com>
>>>>>>> Subject: Re: [PATCH 2/2] lpm: hide internal data
>>>>>>>
>>>>>>> Hi Ruifeng,
>>>>>>>
>>>>>>> On 15/09/2020 17:02, Bruce Richardson wrote:
>>>>>>>> On Mon, Sep 07, 2020 at 04:15:17PM +0800, Ruifeng Wang wrote:
>>>>>>>>> Fields except tbl24 and tbl8 in rte_lpm structure have no need to
>>>>>>>>> be exposed to the user.
>>>>>>>>> Hide the unneeded exposure of structure fields for better ABI
>>>>>>>>> maintainability.
>>>>>>>>>
>>>>>>>>> Suggested-by: David Marchand <david.marchand@redhat.com>
>>>>>>>>> Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
>>>>>>>>> Reviewed-by: Phil Yang <phil.yang@arm.com>
>>>>>>>>> ---
>>>>>>>>>    lib/librte_lpm/rte_lpm.c | 152
>>>>>>>>> +++++++++++++++++++++++---------------
>>>>>>> -
>>>>>>>>>    lib/librte_lpm/rte_lpm.h |   7 --
>>>>>>>>>    2 files changed, 91 insertions(+), 68 deletions(-)
>>>>>>>>>
>>>>>>>> <snip>
>>>>>>>>> diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h
>>>>>>>>> index 03da2d37e..112d96f37 100644
>>>>>>>>> --- a/lib/librte_lpm/rte_lpm.h
>>>>>>>>> +++ b/lib/librte_lpm/rte_lpm.h
>>>>>>>>> @@ -132,17 +132,10 @@ struct rte_lpm_rule_info {
>>>>>>>>>
>>>>>>>>>    /** @internal LPM structure. */
>>>>>>>>>    struct rte_lpm {
>>>>>>>>> -    /* LPM metadata. */
>>>>>>>>> -    char name[RTE_LPM_NAMESIZE];        /**< Name of the lpm. */
>>>>>>>>> -    uint32_t max_rules; /**< Max. balanced rules per lpm. */
>>>>>>>>> -    uint32_t number_tbl8s; /**< Number of tbl8s. */
>>>>>>>>> -    struct rte_lpm_rule_info rule_info[RTE_LPM_MAX_DEPTH]; /**<
>>>>>>> Rule info table. */
>>>>>>>>> -
>>>>>>>>>        /* LPM Tables. */
>>>>>>>>>        struct rte_lpm_tbl_entry tbl24[RTE_LPM_TBL24_NUM_ENTRIES]
>>>>>>>>>                __rte_cache_aligned; /**< LPM tbl24 table. */
>>>>>>>>>        struct rte_lpm_tbl_entry *tbl8; /**< LPM tbl8 table. */
>>>>>>>>> -    struct rte_lpm_rule *rules_tbl; /**< LPM rules. */
>>>>>>>>>    };
>>>>>>>>>
>>>>>>>>
>>>>>>>> Since this changes the ABI, does it not need advance notice?
>>>>>>>>
>>>>>>>> [Basically the return value point from rte_lpm_create() will be
>>>>>>>> different, and that return value could be used by rte_lpm_lookup()
>>>>>>>> which as a static inline function will be in the binary and using
>>>>>>>> the old structure offsets.]
>>>>>>>>
>>>>>>>
>>>>>>> Agree with Bruce, this patch breaks ABI, so it can't be accepted
>>>>>>> without prior notice.
>>>>>>>
>>>>>> So if the change wants to happen in 20.11, a deprecation notice 
>>>>>> should
>>>>>> have been added in 20.08.
>>>>>> I should have added a deprecation notice. This change will have to 
>>>>>> wait for
>>>>> next ABI update window.
>>>>>>
>>>>>
>>>>> Do you plan to extend? or is this just speculative?
>>>> It is speculative.
>>>>
>>>>>
>>>>> A quick scan and there seems to be several projects using some of 
>>>>> these
>>>>> members that you are proposing to hide. e.g. BESS, NFF-Go, DPVS,
>>>>> gatekeeper. I didn't look at the details to see if they are really 
>>>>> needed.
>>>>>
>>>>> Not sure how much notice they'd need or if they update DPDK much, 
>>>>> but I
>>>>> think it's worth having a closer look as to how they use lpm and 
>>>>> what the
>>>>> impact to them is.
>>>> Checked the projects listed above. BESS, NFF-Go and DPVS don't 
>>>> access the members to be hided.
>>>> They will not be impacted by this patch.
>>>> But Gatekeeper accesses the rte_lpm internal members that to be 
>>>> hided. Its compilation will be broken with this patch.
>>>>
>>>>>
>>>>>> Thanks.
>>>>>> Ruifeng
>>>>>>>>>    /** LPM RCU QSBR configuration structure. */
>>>>>>>>> -- 
>>>>>>>>> 2.17.1
>>>>>>>>>
>>>>>>>
>>>>>>> -- 
>>>>>>> Regards,
>>>>>>> Vladimir
>>>>
>>>
> 

  reply index

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-07  8:15 [dpdk-dev] [PATCH 0/2] LPM changes Ruifeng Wang
2020-09-07  8:15 ` [dpdk-dev] [PATCH 1/2] lpm: fix free of data structure Ruifeng Wang
2020-09-15 15:55   ` Bruce Richardson
2020-09-15 16:25   ` Medvedkin, Vladimir
2020-09-07  8:15 ` [dpdk-dev] [PATCH 2/2] lpm: hide internal data Ruifeng Wang
2020-09-15 16:02   ` Bruce Richardson
2020-09-15 16:28     ` Medvedkin, Vladimir
2020-09-16  3:17       ` Ruifeng Wang
2020-09-30  8:45         ` Kevin Traynor
2020-10-09  6:54           ` Ruifeng Wang
2020-10-13 13:53             ` Kevin Traynor
2020-10-13 14:58               ` Michel Machado
2020-10-13 15:41                 ` Medvedkin, Vladimir
2020-10-13 17:46                   ` Michel Machado [this message]
2020-10-13 19:06                     ` Medvedkin, Vladimir
2020-10-13 19:48                       ` Michel Machado
2020-10-14 13:10                         ` Medvedkin, Vladimir
2020-10-14 23:57                           ` Honnappa Nagarahalli
2020-10-15 13:39                             ` Michel Machado
2020-10-15 17:38                               ` Honnappa Nagarahalli
2020-10-15 19:30                                 ` Medvedkin, Vladimir
2020-10-15 22:54                                   ` Honnappa Nagarahalli
2020-10-16 11:39                                     ` Kevin Traynor
2020-10-16 13:55                                       ` Michel Machado
2020-10-19 14:53                                     ` David Marchand
2020-10-20 14:22                                       ` Thomas Monjalon
2020-10-20 14:32                                         ` Medvedkin, Vladimir
2020-10-19 17:53             ` Honnappa Nagarahalli
2020-09-15 14:41 ` [dpdk-dev] [PATCH 0/2] LPM changes David Marchand
2020-10-19 13:37   ` Kevin Traynor
2020-10-21  3:02 ` [dpdk-dev] [PATCH v2 " Ruifeng Wang
2020-10-21  3:02   ` [dpdk-dev] [PATCH v2 1/2] lpm: fix free of data structure Ruifeng Wang
2020-10-21  3:02   ` [dpdk-dev] [PATCH v2 2/2] lpm: hide internal data Ruifeng Wang
2020-10-21  7:58     ` Thomas Monjalon
2020-10-21  8:15       ` Ruifeng Wang
2020-10-22 15:14     ` David Marchand
2020-10-23  6:13       ` Ruifeng Wang
2020-10-23 16:08         ` Medvedkin, Vladimir
2020-10-23  9:38 ` [dpdk-dev] [PATCH v3 0/2] LPM changes David Marchand
2020-10-23  9:38   ` [dpdk-dev] [PATCH v3 1/2] lpm: fix free of data structure David Marchand
2020-10-23  9:38   ` [dpdk-dev] [PATCH v3 2/2] lpm: hide internal data David Marchand
2020-10-26  8:26   ` [dpdk-dev] [PATCH v3 0/2] LPM changes David Marchand

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