DPDK patches and discussions
 help / color / mirror / Atom feed
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 15:48:46 -0400	[thread overview]
Message-ID: <f95bf756-70be-9df5-1d9d-e8c2b0addbf9@digirati.com.br> (raw)
In-Reply-To: <9197371c-5e03-4852-d62a-6456f0b762f0@intel.com>

On 10/13/20 3:06 PM, Medvedkin, Vladimir wrote:
> 
> 
> On 13/10/2020 18:46, Michel Machado wrote:
>> 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.
> 
> Aha, thanks. So do I understand correctly that you need to add a set of 
> routes atomically (either the entire set is installed or nothing)?

    Yes.

> If so, then I would suggest having 2 lpm and switching them atomically 
> after a successful addition. As for now, even if you have enough tbl8's, 
> routes are installed non atomically, i.e. there will be a time gap 
> between adding two routes, so in this time interval the table will be 
> inconsistent with the policy.
> Also, if new lpm algorithms are added to the DPDK, they won't have such 
> a thing as tbl8.

    Our code already deals with synchronization.

>>     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.
>>
> 
> Usually, the table is initialized with a large enough number of entries, 
> enough to add a possible number of routes. One tbl8 group takes up 1Kb 
> of memory which is nothing comparing to the size of tbl24 which is 64Mb.

    When the prefixes come from BGP, initializing a large enough table 
is fine. But when prefixes come from threat intelligence, the number of 
prefixes can vary wildly and the number of prefixes above 24 bits are 
way more common.

> P.S. consider using rte_fib library, it has a number of advantages over 
> LPM. You can replace the loop in __lookup_fib_bulk() with a bulk lookup 
> call and this will probably increase the speed.

    I'm not aware of the rte_fib library. The only documentation that I 
found on Google was https://doc.dpdk.org/api/rte__fib_8h.html and it 
just says "FIB (Forwarding information base) implementation for IPv4 
Longest Prefix Match".

>>>
>>> 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	other threads:[~2020-10-13 21:04 UTC|newest]

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
2020-10-13 19:06                     ` Medvedkin, Vladimir
2020-10-13 19:48                       ` Michel Machado [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=f95bf756-70be-9df5-1d9d-e8c2b0addbf9@digirati.com.br \
    --to=michel@digirati.com.br \
    --cc=Honnappa.Nagarahalli@arm.com \
    --cc=Ruifeng.Wang@arm.com \
    --cc=andre@digirati.com.br \
    --cc=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    --cc=doucette@bu.edu \
    --cc=ktraynor@redhat.com \
    --cc=mengxiang0811@gmail.com \
    --cc=nd@arm.com \
    --cc=vladimir.medvedkin@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).