[dpdk-dev] rte_flow ageing
David Bouyeure
david.bouyeure at fraudbuster.mobi
Wed Apr 7 18:19:34 CEST 2021
Hi Matan, and thanks a lot,
regarding the mode *1*, I still have a doubt:
>
> 1. Register the AGE event -> in event time to query the aged-out
> flows by the rte_flow_get_aged_flows API, this call will trigger a
> new event when new aged-out flow will be detected for the port.(if
> you don’t call rte_flow_get_aged_flows the event will not be
> retriggered.)
>
You meant calling rte_flow_get_aged_flows() from the event callback I
guess...?
I think this is not working because MLX5_AGE_TRIGGER is erased when the
callback returns.
Anyway, the polling mode is enough to me so far.
Thanks again.
Regards.
On 4/5/21 12:23 PM, Matan Azrad wrote:
>
> Hi
>
> I will try to answer inline with prefix [MA].
>
> *From:* David Bouyeure <david.bouyeure at fraudbuster.mobi>
> *Sent:* Tuesday, March 30, 2021 6:46 PM
> *To:* Asaf Penso <asafp at nvidia.com>; dev at dpdk.org
> *Cc:* Matan Azrad <matan at nvidia.com>; Jack Min <jackmin at nvidia.com>
> *Subject:* Re: [dpdk-dev] rte_flow ageing
>
> *External email: Use caution opening links or attachments*
>
> Thanks a lot Asaf, for your answer, so fast.
>
> depending on the feature we want, the table you mentioned in the doc
> may give different combinations. Mine, DPDK-20.08/OFED 5.1-2, is part
> of the list.
>
> Anyway, my question is more about the API design. Please, find my
> comments below.
>
> On 3/29/21 8:02 PM, Asaf Penso wrote:
>
> Hello David,
>
> Thanks for reaching out, I'll try to answer as best as I know and I added Matan who will be able to provide further info during next week.
>
> First, according to our pmd documentation (http://doc.dpdk.org/guides/nics/mlx5.html#supported-hardware-offloads <https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdoc.dpdk.org%2Fguides%2Fnics%2Fmlx5.html%23supported-hardware-offloads&data=04%7C01%7Cmatan%40nvidia.com%7Cdfc24177f1fa4209c81f08d8f392e4c2%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637527159538915512%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=8xI9xcx8uhHTBDr22aZi986oXyTHTN8E6NKsx%2BYMqAQ%3D&reserved=0>) we recommend using DPDK20.11 and OFED5.2, and not the combo you are referring to.
>
> Second, we can always improve our documentation and I appreciate your queries.
>
> Please see my comments inline.
>
> Regards,
>
> Asaf Penso
>
> -----Original Message-----
>
> From: dev<dev-bounces at dpdk.org> <mailto:dev-bounces at dpdk.org> On Behalf Of David Bouyeure
>
> Sent: Monday, March 29, 2021 11:35 AM
>
> To:dev at dpdk.org <mailto:dev at dpdk.org>
>
> Subject: [dpdk-dev] rte_flow ageing
>
> Hi,
>
> I've found out the pretty useful experimental brand new flow ageing API
>
> implemented in the mlx5 PMD.
>
> It is useful and I hope you'll fully understand at the end why😊
>
>
>
> I'm trying it (rte_eth_dev_callback_register(RTE_ETH_EVENT_FLOW_AGED),
>
> RTE_FLOW_ACTION_TYPE_AGE) to recover any flow that I previously
>
> offloaded.
>
> The DPDK version is 20.08 and Mellanox(Connect-X6) OFED drivers are 5.1-
>
> 2.5.8.0.
>
> See above the suggested versions for this feature
>
> I eventually don't see the usefulness of the callback since it's actually triggered
>
> indirectly by us(the DPDK application) when calling
>
> rte_flow_get_aged_flows().
>
> The main intention is to offload the aging logic from the application level to the pmd level.
>
> There is so saving of cpu cycles, and the gain here is with simplicity.
>
> The application doesn't need to have complex logic of comparison between counters or other HW info that can be retrieve.
>
> Now, the pmd hides all of that and leaves the application only to decide what to do with the flows that are aged out.
>
> Please note, the pmd does not delete any flow, just provide the list of all the flows that are aged.
>
> I fully understand that and this is a very very useful feature to us.
>
> If we don't call it, the callback is called only once.
>
> And, calling rte_flow_get_aged_flows() from the callback won't trigger it next
>
> time(MLX5_AGE_TRIGGER is reset after the callback call)
>
> Once you call the function the pmd will not trigger more events. Now it's up to the application to decide what to do.
>
> Doing it differently, will cause an interrupt storm and the pmd avoids that.If new flows are aged then the pmd will trigger a new event.
>
> Sorry, I wasn't realizing that the callback isn't called for each flow
> but rather for each port, though it's clear in the PMD code. But, the
> fact that we can register several RTE_ETH_EVENT_FLOW_AGED event
> handlers is surprising.
>
> [MA] Yes you can register the event for each port support aging if you
> want your callback will be called for “new” aged flows.
>
> So, you suggest to use the callback as an indicator to later retrieve
> the aged-out flows, that's it?
>
> [MA] the user has 2 options:
>
> 1. Register the AGE event -> in event time to query the aged-out
> flows by the rte_flow_get_aged_flows API, this call will trigger a
> new event when new aged-out flow will be detected for the port.(if
> you don’t call rte_flow_get_aged_flows the event will not be
> retriggered.)
> 2. Just call rte_flow_get_aged_flows from time to time(application
> polling).
>
> Wouldn't calling rte_flow_get_aged_flows with NULL param just to get
> the number of aged_flows do the same, without the need to un/register
> a callback, and DPDK to call it?
>
> [MA]
>
> Here, application need to do polling all the time (option 2), in
> option 1 application invest effort only when aged-out flows are detected.
>
> In option 1, you can call it with NULL also in order to know what is
> the array size you need for the actual call.
>
> Another thing, the explanation here
> http://doc.dpdk.org/api/rte__flow_8h.html#a43763e0794d2696b18b6272619aafc2a
> <https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdoc.dpdk.org%2Fapi%2Frte__flow_8h.html%23a43763e0794d2696b18b6272619aafc2a&data=04%7C01%7Cmatan%40nvidia.com%7Cdfc24177f1fa4209c81f08d8f392e4c2%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637527159538925502%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=h0Vp1jtf9NKmgywkL4LLOuSDxLR4VzqPH6mS6aD0%2FyI%3D&reserved=0>
> *"...to get the aged flows usynchronously from the event callback..."*
> seems wrong to me because age_info->flags is set to 0 just after the
> callback, thus ML5_AGE_TRIGGER is canceled and no event will be
> triggered before we'll call rte_flow_get_aged_flows() outside of the
> callback.
>
> [MA] It just say you can choose one of the options *usynchronously
> (option 1), synchronously (option 2).*
>
> Matan
>
> Furthermore, I don't see the point of computing ageing flows in
>
> mlx5_fow.c::mlx5_flow_aging_check() if the client callback isn't called.
>
> Can you elaborate? I'm not sure I understand your intention.
>
> Please forgot :-)
>
> So far, I can handle the flow ageing from the same thread as the one which is
>
> handling the flow direction(rte_flow), it even avoid threads synchronization.
>
> But, in the future, I may need to be noticed as soon as possible of a single flow
>
> ageing, and thus handle this flow logic from the ageing callback.
>
> I may misunderstand the whole ageing API... Thanks a lot for any clarification.
>
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