Re: [dpdk-dev] [PATCH] [RFC] ethdev: support flow aging

[Jerin Jacob Kollanukkaran <jerinj@marvell.com>]

> -----Original Message-----
> From: Matan Azrad <matan@mellanox.com>
> Sent: Thursday, June 6, 2019 4:22 PM
> To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; Adrien Mazarguil
> <adrien.mazarguil@6wind.com>; dev@dpdk.org
> Subject: [EXT] RE: [PATCH] [RFC] ethdev: support flow aging
> 
> Hi Jerin

Hi Matan,

> 
> From: Jerin Jacob
> > > -----Original Message-----
> > > From: dev <dev-bounces@dpdk.org> On Behalf Of Matan Azrad
> > > Sent: Sunday, May 26, 2019 3:48 PM
> > > To: Adrien Mazarguil <adrien.mazarguil@6wind.com>; dev@dpdk.org
> > > Subject: [dpdk-dev] [PATCH] [RFC] ethdev: support flow aging
> > >
> > > One of the reasons to destroy a flow is the fact that no packet
> > > matches the flow for "timeout" time.
> > > For example, when TCP\UDP sessions are suddenly closed.
> > >
> > > Currently, there is no any dpdk mechanism for flow aging and the
> > > applications use there own ways to detect and destroy aged-out flows.
> > >
> > > This RFC introduces flow aging APIs to offload the flow aging task
> > > from the application to the port.
> > >
> > > Design:
> > > - A new rte_flow action: RTE_FLOW_ACTION_TYPE_AGE to set the
> timeout
> > > and
> > >   the application flow context for each flow.
> > > - A new ethdev event: RTE_ETH_EVENT_FLOW_AGED for the driver to
> > report
> > >   that there are new aged-out flows.
> > > - A new rte_flow API: rte_flow_get_aged_flows to get the aged-out
> flows
> > >   contexts from the port.
> > >
> > > By this design each PMD can use its best way to do the aging with
> > > the device offloads supported by its HW.
> > >
> > > Signed-off-by: Matan Azrad <matan@mellanox.com>
> > > ---
> > >  lib/librte_ethdev/rte_ethdev.h |  1 +
> > >  lib/librte_ethdev/rte_flow.h   | 56
> > > ++++++++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 57 insertions(+)
> > >
> > > diff --git a/lib/librte_ethdev/rte_ethdev.h
> > > b/lib/librte_ethdev/rte_ethdev.h index 1f35e1d..6fc1531 100644
> > > --- a/lib/librte_ethdev/rte_ethdev.h
> > > +++ b/lib/librte_ethdev/rte_ethdev.h
> > > @@ -2771,6 +2771,7 @@ enum rte_eth_event_type {
> > >  	RTE_ETH_EVENT_NEW,      /**< port is probed */
> > >  	RTE_ETH_EVENT_DESTROY,  /**< port is released */
> > >  	RTE_ETH_EVENT_IPSEC,    /**< IPsec offload related event */
> > > +	RTE_ETH_EVENT_FLOW_AGED,/**< New aged-out flows detected in
> > > the port
> > Does this event supported in HW?
> It depends in the PMD implementation and HW capability.
> 
> > Or Are planning to implement with alarm or timer.
> Again, depends in the PMD implementation.
> 
> > Just asking because, if none of the HW supports the interrupt then
> > only rte_flow_get_aged_flows sync API be enough()
> Why?

If none of the HW supports it then application/common code can periodically polls it.
If mlx5 hw supports it then it fine to have interrupt. 
But I think, we need to have means to express a HW/Implementation does not support its
As there may following reasons why drivers choose to not take timer/alarm path 
1) Some EAL port does not support timer/alarm example: FreeBSD DPDK port
2) If we need to support a few killo rules then timer/alarm implementation will be heavy
So an option to express un supported event would be fine.

> 
> According to the above design this is the way for the PMD to notify the
> application when it has some aged flows ASAP.
> So, if the PMD uses an alarm\timer or any other way to support aging action
> it is better in part of the cases to notify the user asynchronically instead of
> doing polling by the application.
> The idea is to let the application to decide what is better for its usage.
> 
> For mlx5 case,
> The plan is to raise this event from an HW interrupt handling(same as link
> event).

Good to know.

> 
> Matan.
> 
> 
> 
> 
> 
> 
>