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

[Ori Kam <orika@mellanox.com>]

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?
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