[PATCH v4 3/3] ethdev: add standby flags for live migration

[Rongwei Liu]

Hi Jerin:

BR
Rongwei

> -----Original Message-----
> From: Jerin Jacob <jerinjacobk at gmail.com>
> Sent: Tuesday, January 31, 2023 16:46
> To: Rongwei Liu <rongweil at nvidia.com>
> Cc: dev at dpdk.org; Matan Azrad <matan at nvidia.com>; Slava Ovsiienko
> <viacheslavo at nvidia.com>; Ori Kam <orika at nvidia.com>; NBU-Contact-
> Thomas Monjalon (EXTERNAL) <thomas at monjalon.net>;
> stephen at networkplumber.org; Raslan Darawsheh <rasland at nvidia.com>;
> Ferruh Yigit <ferruh.yigit at amd.com>; Andrew Rybchenko
> <andrew.rybchenko at oktetlabs.ru>
> Subject: Re: [PATCH v4 3/3] ethdev: add standby flags for live migration
> 
> External email: Use caution opening links or attachments
> 
> 
> On Tue, Jan 31, 2023 at 8:23 AM Rongwei Liu <rongweil at nvidia.com> wrote:
> >
> > HI Jerin:
> >
> > BR
> > Rongwei
> >
> > > -----Original Message-----
> > > From: Jerin Jacob <jerinjacobk at gmail.com>
> > > Sent: Tuesday, January 31, 2023 01:10
> > > To: Rongwei Liu <rongweil at nvidia.com>
> > > Cc: dev at dpdk.org; Matan Azrad <matan at nvidia.com>; Slava Ovsiienko
> > > <viacheslavo at nvidia.com>; Ori Kam <orika at nvidia.com>; NBU-Contact-
> > > Thomas Monjalon (EXTERNAL) <thomas at monjalon.net>;
> > > stephen at networkplumber.org; Raslan Darawsheh <rasland at nvidia.com>;
> > > Ferruh Yigit <ferruh.yigit at amd.com>; Andrew Rybchenko
> > > <andrew.rybchenko at oktetlabs.ru>
> > > Subject: Re: [PATCH v4 3/3] ethdev: add standby flags for live
> > > migration
> > >
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > On Mon, Jan 30, 2023 at 8:17 AM Rongwei Liu <rongweil at nvidia.com>
> wrote:
> > > >
> > > > Hi Jerin
> > > >
> > > > BR
> > > > Rongwei
> > > >
> > > > > -----Original Message-----
> > > > > From: Jerin Jacob <jerinjacobk at gmail.com>
> > > > > Sent: Monday, January 23, 2023 21:20
> > > > > To: Rongwei Liu <rongweil at nvidia.com>
> > > > > Cc: dev at dpdk.org; Matan Azrad <matan at nvidia.com>; Slava
> > > > > Ovsiienko <viacheslavo at nvidia.com>; Ori Kam <orika at nvidia.com>;
> > > > > NBU-Contact- Thomas Monjalon (EXTERNAL) <thomas at monjalon.net>;
> > > > > stephen at networkplumber.org; Raslan Darawsheh
> > > > > <rasland at nvidia.com>; Ferruh Yigit <ferruh.yigit at amd.com>;
> > > > > Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>
> > > > > Subject: Re: [PATCH v4 3/3] ethdev: add standby flags for live
> > > > > migration
> > > > >
> > > > > External email: Use caution opening links or attachments
> > > > >
> > > > >
> > > > > On Wed, Jan 18, 2023 at 9:15 PM Rongwei Liu
> > > > > <rongweil at nvidia.com>
> > > wrote:
> > > > > >
> > > > > > Some flags are added to the process state API for live
> > > > > > migration in order to change the behavior of the flow rules in a
> standby process.
> > > > > >
> > > > > > Signed-off-by: Rongwei Liu <rongweil at nvidia.com>
> > > > > > ---
> > > > > >  lib/ethdev/rte_ethdev.h | 21 +++++++++++++++++++++
> > > > > >  1 file changed, 21 insertions(+)
> > > > > >
> > > > > > diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
> > > > > > index
> > > > > > 1505396ced..9ae4f426a7 100644
> > > > > > --- a/lib/ethdev/rte_ethdev.h
> > > > > > +++ b/lib/ethdev/rte_ethdev.h
> > > > > > @@ -2260,6 +2260,27 @@ int rte_eth_dev_owner_get(const
> > > > > > uint16_t port_id,  __rte_experimental  int
> > > > > > rte_eth_process_set_role(bool standby, uint32_t flags);
> > > > > >
> > > > > > +/**@{@name Process role flags
> > > > > > + * used when migrating from an application to another one.
> > > > > > + * @see rte_eth_process_set_active  */
> > > > > > +/**
> > > > > > + * When set on a standby process, ingress flow rules will be
> > > > > > +effective
> > > > > > + * in active and standby processes, so the ingress traffic
> > > > > > +may be
> > > duplicated.
> > > > > > + */
> > > > > > +#define RTE_ETH_PROCESS_FLAG_STANDBY_DUP_FLOW_INGRESS
> > > > > RTE_BIT32(0)
> > > > >
> > > > >
> > > > > How to duplicate if action has statefull items for example,
> > > > > rte_flow_action_security::security_session -> it store the live
> > > > > pointer rte_flow_action_meter::mtr_id; -> MTR object ID created
> > > > > with
> > > > > rte_mtr_create()
> > > > I agree with you, not all actions can be supported in the
> > > > active/standby
> > > model.
> > >
> > > IMO, Where ever rules are not standalone (like QUEUE, RSS) etc, It
> > > will be architecturally is not possible to migrate with pointers.
> > > That's where I have concern generalizing this feature for this ethdev.
> > >
> > Not sure I understand your concern correctly. What' the pointer concept
> here?
> 
> I meant, Any HW resource driver deals with "pointers" or "fixed ID"
> can not get the same value
> for the new application. That's where I believe this whole concepts works for
> very standalone rte_flow patterns and actions.
> 
> 
> > Queue RSS actions can be migrated per my local test. Active/Standby
> application have its fully own rxq/txq.
> 
> Yes. It because it is standalone.
> 
> > They are totally separated processes and like two members in pipeline. 2nd
> member can't be feed if 1st member alive and handle the traffic.
> >
> > > Also, I don't believe there is any real HW support needed for this.
> > > IMO, Having DPDK standard multiprocess can do this by keeping
> > > secondary application can migrate, keeping all the SW logic in the
> > > primary process by doing the housekeeping in the application. On
> > > plus side, it works with pointers too.
> 
> > IMO, in multiple process model, primary process usually owns the hardware
> resources via mmap/iomap/pci_map etc.
> > Secondary process is not able to run if primary quits no matter gracefully or
> crashing.
> > This patch wants to introduce a "backup to alive" model.
> > Assume user wants to upgrade from DPDK version 22.03 to 23.03, 22.03 is
> running and active role while 23.03 comes up in standby.
> > Both DPDK processes have its own resources and doesn't rely on each other.
> > User can migrate the application following the steps in commit message
> with minimum traffic downtime.
> > SW logic like flow rules can be done following iptables-save/iptables-restore
> approach.
> > >
> > > I am not sure how much housekeeping offload to _HW_ in your case. In
> > > my view, it should be generic utils functions to track the flow and
> > > installing the rules using rte_flow APIs and keep the scope only for
> rte_flow.
> > For rules part, totally agree with you. Issue is there maybe millions
> > of flow rules in field and each rule may take different steps to re-install per
> vendor' implementations.
> 
> I understand the desire for millon flow migrations. Which makes sense.IMO, It
> may be just easy to make this feature just for rte_flow name space. Just have
> APIs to export() existing rules for the given port and import() the rules
> exported rather than going to ethdev space and call it as "live migration".
> 
Do you mean the API naming should be "rte_flow_process_set_role()" instead of "rte_eth_process_set_role()" ?
Also move to rte_flow.c/.h files? Are we good to keep the PMD callback in eth_dev layer?
Simple export()/import() may not work. Image some flow rules are exclusive and can't be issued from both applications. 
We need to stop old application. I am afraid this will introduce big time window which traffic stops. 
Application won't like this behavior.
With this callback, each PMD can specify each rule, queue it or use lower priority if exclusive. Or return error.

> > This serial wants to propose a unified interface for upper layer application'
> easy use.
> > >
> > > That's just my view. I leave to ethdev maintainers for the rest of
> > > the review and decision on this series.
> > >
> > > > That' why we have return value checking and rollback.
> > > > In Nvidia driver doc, we suggested user to start from 'rss/queue/jump'
> > > actions.
> > > > Meter is possible, at least per my view.
> > > > Assume: "meter g_action queue 0 / y_action drop / r_action drop"
> > > > Old application: create meter_id 'A' with pre-defined limitation.
> > > > New application: create meter_id 'B' which has the same parameters
> > > > with
> > > 'A'.
> > > > 1. 1st possible approach:
> > > >         Hardware duplicates the traffic; old application use meter
> > > > 'A' and new
> > > application uses meter 'B' to control traffic throughputs.
> > > >         Since traffic is duplicated, so it can go to different meters.
> > > > 2. 2nd possible approach:
> > > >              Meter 'A' and 'B' point to the same hardware
> > > > resource, and traffic
> > > reaches this part first and if green, duplication happens.