Re: [dpdk-dev] [PATCH] add flow shared action API

[Jerin Jacob <jerinjacobk@gmail.com>]

On Wed, Jul 8, 2020 at 2:33 AM Ori Kam <orika@mellanox.com> wrote:
>
> Hi Jerin,

Hi Ori,

>
> > -----Original Message-----
> > From: Jerin Jacob <jerinjacobk@gmail.com>
> >
> > On Tue, Jul 7, 2020 at 11:51 AM Ori Kam <orika@mellanox.com> wrote:
> > >
> > > Hi Jerin,
> > >  Thanks you for your quick reply.
> > >
> > > > -----Original Message-----
> > > > From: Jerin Jacob <jerinjacobk@gmail.com>
> > > > Subject: Re: [dpdk-dev] [PATCH] add flow shared action API
> > > >
> > > > On Mon, Jul 6, 2020 at 7:02 PM Andrey Vesnovaty
> > > > <andrey.vesnovaty@gmail.com> wrote:
> > > > >
> > > > > Hi, Jerin.
> > > >
> > > > Hi Ori and Andrey,
> > > >
> > > >
> > > > >
> > > > > Please see below Ori's suggestion below to implement your
> > > > rte_flow_action_update() idea
> > > > > with some API changes of rte_flow_shared_action_xxx API changes.
> > > > >
> > > > > On Mon, Jul 6, 2020 at 3:28 PM Ori Kam <orika@mellanox.com> wrote:
> > > > >>
> > > > >> Hi Jerin,
> > > > >>
> > > > >> > -----Original Message-----
> > > > >> > From: Jerin Jacob <jerinjacobk@gmail.com>
> > > > >> > Sent: Monday, July 6, 2020 12:00 PM
> > > > >> > Subject: Re: [dpdk-dev] [PATCH] add flow shared action API
> > > > >> >
> > > > >> > On Sun, Jul 5, 2020 at 3:56 PM Ori Kam <orika@mellanox.com> wrote:
> > > > >> > >
> > > > >> > > Hi Jerin,
> > > > >> > > PSB,
> > > > >> > >
> > > > >> > > Thanks,
> > > > >> > > Ori
> > > > >> > >
> > > > >> > > > -----Original Message-----
> > > > >> > > > From: Jerin Jacob <jerinjacobk@gmail.com>
> > > > >> > > > Sent: Saturday, July 4, 2020 3:33 PM
> > > > >> > > > dpdk-dev <dev@dpdk.org>
> > > > >> > > > Subject: Re: [dpdk-dev] [PATCH] add flow shared action API
> > > > >> > > >
> > > > >> > > > On Sat, Jul 4, 2020 at 3:40 PM Andrey Vesnovaty
> > > > >> > > > <andrey.vesnovaty@gmail.com> wrote:
> > > > >> > > > >
> > > > >> > > > >
> > > > >> > > > > Thanks,
> > > > >> > > > >
> > > > >> > > > > Andrey Vesnovaty
> > > > >> > > > > (+972)526775512 | Skype: andrey775512
> > > > >> > > > >
> > > > >> > >
> > > > >> > >
> > > > >> > > [..Nip ..]
> > > > >> > >
> > > > >> > > > > I need to mention the locking issue once again.
> > > > >> > > > > If there is a need to maintain "shared session" in the generic
> > > > rte_flow
> > > > >> > layer
> > > > >> > > > all
> > > > >> > > > > calls to flow_create() with shared action & all delete need to take
> > > > >> > > > sharedsession
> > > > >> > > > > management locks at least for verification. Lock partitioning is
> > also
> > > > bit
> > > > >> > > > problematic
> > > > >> > > > > since one flow may have more than one shared action.
> > > > >> > > >
> > > > >> > > > Then, I think better approach would be to introduce
> > > > >> > > > rte_flow_action_update() public
> > > > >> > > > API which can either take "const struct rte_flow_action []" OR
> > shared
> > > > >> > > > context ID, to cater to
> > > > >> > > > both cases or something on similar lines. This would allow HW's
> > > > >> > > > without have  the shared context ID
> > > > >> > > > to use the action update.
> > > > >> > >
> > > > >> > > Can you please explain your idea?
> > > > >> >
> > > > >> > I see two types of HW schemes supporting action updates without
> > going
> > > > >> > through call `rte_flow_destroy()` and call `rte_flow_create()`
> > > > >> > - The shared HW action context feature
> > > > >> > - The HW has "pattern" and "action" mapped to different HW objects
> > and
> > > > >> > action can be updated any time.
> > > > >> > Other than above-mentioned RSS use case, another use case would be
> > to
> > > > >> > a) create rte_flow and set the action as DROP (Kind of reserving the
> > HW
> > > > object)
> > > > >> > b) Update the action only when the rest of the requirements ready.
> > > > >> >
> > > > >> > Any API schematic that supports both notions of HW is fine with me.
> > > > >> >
> > > > >> I have an idea if the API will be changed to something like this,
> > > > >> Rte_flow_shared_action_update(uint16_port port, rte_shared_ctx *ctx,
> > > > rte_flow_action *action, error)
> > > > >> This will enable the application to send a different action than the
> > original
> > > > one to be switched.
> > > > >> Assuming the PMD supports this.
> > > > >> Does it answer your concerns?
> > > > >
> > > > >
> > > > > This allows both:
> > > > > 1. Update action configuration
> > > > > 2. Replace action by some other action
> > > > > For 2 pure software implementation may carate shred action (that can be
> > > > shared
> > > > > with one flow only, depends on PMD) and later on
> > > > rte_flow_shared_action_update may replace this
> > > > > action with some other action by handle returned from
> > > > rte_flow_shared_action_create
> > > > > Doesign between 1 and 2 is per PMD.
> > > >
> > > > struct rte_flow * object holds the driver representation of the
> > > > pattern + action.
> > > > So in order to update the action, we would need struct rte_flow * in API.
> > > >
> > > Why is that? The idea is to change the action, the action itself is connected to
> > flows.
> > > The PMD can save in the shared_ctx all flows that are connected to this
> > action.
> > >
> > > > I think, simple API change would be to accommodate "rte_shared_ctx
> > > > *ctx, rte_flow_action *action" modes
> > > > without introducing the emulation for one or other mode, will be.
> > > >
> > > > enum rte_flow_action_update_type {
> > > >               RTE_FLOW_ACTION_UPDATE_TYPE_SHARED_ACTION,
> > > >               RTE_FLOW_ACTION_UPDATE_TYPE_ACTION,
> > > > };
> > > >
> > > > struct rte_flow_action_update_type_param {
> > > >          enum rte_flow_action_update_type type;
> > > >          union {
> > > >                      struct rte_flow_action_update_type_shared_action_param {
> > > >                                 rte_shared_ctx *ctx;
> > > >                       } shared_action;
> > > >                       struct rte_flow_action_update_type_shared_action_param {
> > > >                                 rte_flow *flow,
> > > >                                  rte_flow_action *action;
> > > >                       } action;
> > > >          }
> > > > }
> > > >
> > > Thank you for the idea but I fall to see how your suggested API is simpler than
> > the one suggested by me?
> >
> > My thought process with the below-proposed API[1] is that It is
> > dictates "_shared_action_" in API name as
> > well as arguments. I just thought of expressing it as either-or case
> > hence I thought [2] is better. i.e The PMD does not support
> > shared_action, not even need to create one to use
> > rte_flow_action_update() to avoid the confusion. Thoughts?
> >
> > [1]
> > rte_flow_shared_action_update(uint16_port port, rte_shared_ctx *ctx,
> > rte_flow_action *action, error)
> >
> > [2]
> > rte_flow_action_update(uint16_port port, struct
> > rte_flow_action_update_type_param  *param, error)
> >
> Let me see if I understand you correctly, your suggestion is to allow
> the application to change one action in one flow, but instead of creating
> the context the application will just supply the rte_flow and the new actions
> do I understand correctly?

Yes.

>
> If so this it is a nice idea, but there are some issues with it,
> 1. The PMD must save the flow which will result in memory consumption.

struct rte_flow * driver handle any way store that information to as
it would be needed
for other rte_flow related APIs.


> 2. Assume that two flows are using the same RSS action for example, so the PMD
> reuse the RSS object he created for the first flow also for the second. Now changing
> this RSS flow may result in also changing the second flow. (this can be solved by always
> creating new action)

It is not resuing the action, it more of updating the action. So the
above said issue won't happen.
It is removing the need for  call `rte_flow_destroy()` and call
`rte_flow_create()` if only action
needs to update for THE given flow. That's it.


> 3. It doesn't handle the main use case that the application wants to change number of
> flows at the same time, which is the idea of this feature.

We discussed this in detail and tried approach for the common code to
make everything
as shared action. Andrey quickly realizes that it is difficult without
HW support.

>
> I also think that all PMD that support option 2 can  support option 1 since
> they can save in the ctx a list of flows and simply apply them again. So by
> definition if PMD supports [2] it also support [1] while the other
> way is not correct since it forces the PMD to save flows which like I said waste memory.

If we use "rte_flow_shared_action_update(uint16_port port,
rte_shared_ctx *ctx,  rte_flow_action *action, error)",
What would be ctx value for the HW does not support a shared context?
That's is the only reason for
my proposal.  I understand, your concern about supporting two modes in
PMD, I don't think,
PMD needs to support RTE_FLOW_ACTION_UPDATE_TYPE_ACTION if
RTE_FLOW_ACTION_UPDATE_TYPE_SHARED_ACTION supported.

>
> I suggest that we will go with option [1], and if needed in the future we will update the code.
> using option [2] will result in dead code since at least for the current time no PMD will implement this
> API.

We are planning to update our PMD to support this once API is finalized.

>
> I can suggest one more thing maybe to change the name from shared_ctx to just ctx
> which implicitly mean it can be shared but not a must. What do you think? (but again
> I think by definition if a PMD can implement number [2] it can also implement it to number
> of flows using API [2].

Just void *type is fine too, but we need an argument for type to cast
it in application and/or driver.

 enum rte_flow_action_update_type {
              RTE_FLOW_ACTION_UPDATE_TYPE_SHARED_ACTION,
              RTE_FLOW_ACTION_UPDATE_TYPE_ACTION,
 };

>
> > > In my suggestion the PMD simply needs to check if the new action and
> > change the
> > > context and to that action, or just change parameters in the action, if it is the
> > same action.
> > >
> > > Let's go with the original patch API modified to support like you requested
> > also changing the action,
> > > based on my comments.
> > >
> > > > rte_flow_action_update(uint16_port port, struct
> > > > rte_flow_action_update_type_param  *param, error)
> > > >
> > > > >
> [..nip..]
>
> Best,
> Ori