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

[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)

> 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)
> >
> > >
> > >>
> > >> >
> > >> > > As I can see if we use the flow_action array it may result in bugs.
> > >> > > For example, the application created two flows with the same RSS (not
> > using
> > >> > the context)
> > >> > > Then he wants to change one flow to use different RSS, but the result will
> > that
> > >> > both flows
> > >> > > will be changed.
> > >> >
> > >> > Sorry. I don't quite follow this.
> > >> >
> > >> I was trying to show that there must be some context. But I don’t think this is
> > relevant to
> > >> your current ideas.
> > >>
> > >> > > Also this will enforce the PMD to keep track on all flows which will have
> > >> > memory penalty for
> > >> > > some PMDs.
> > >>
> > >> Best,
> > >> Ori
> > >
> > >
> > > Thanks,
> > > Andrey
> Best,
> Ori