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From: Thomas Monjalon <thomas@monjalon.net>
To: Neil Horman <nhorman@tuxdriver.com>
Cc: dev@dpdk.org, Matan Azrad <matan@mellanox.com>,
	Bruce Richardson <bruce.richardson@intel.com>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	Gaetan Rivet <gaetan.rivet@6wind.com>,
	"Wu, Jingjing" <jingjing.wu@intel.com>
Subject: Re: [dpdk-dev] [PATCH v2 2/6] ethdev: add port ownership
Date: Fri, 19 Jan 2018 21:19:18 +0100	[thread overview]
Message-ID: <2018230.dXJnJTqQbo@xps> (raw)
In-Reply-To: <20180119194739.GF9519@hmswarspite.think-freely.org>

19/01/2018 20:47, Neil Horman:
> On Fri, Jan 19, 2018 at 07:12:36PM +0100, Thomas Monjalon wrote:
> > 19/01/2018 18:43, Neil Horman:
> > > On Fri, Jan 19, 2018 at 06:17:51PM +0100, Thomas Monjalon wrote:
> > > > 19/01/2018 16:27, Neil Horman:
> > > > > On Fri, Jan 19, 2018 at 03:13:47PM +0100, Thomas Monjalon wrote:
> > > > > > 19/01/2018 14:30, Neil Horman:
> > > > > > > So it seems like the real point of contention that we need to settle here is,
> > > > > > > what codifies an 'owner'.  Must it be a specific execution context, or can we
> > > > > > > define any arbitrary section of code as being an owner?  I would agrue against
> > > > > > > the latter.
> > > > > > 
> > > > > > This is the first thing explained in the cover letter:
> > > > > > "2. The port usage synchronization will be managed by the port owner."
> > > > > > There is no intent to manage the threads synchronization for a given port.
> > > > > > It is the responsibility of the owner (a code object) to configure its
> > > > > > port via only one thread.
> > > > > > It is consistent with not trying to manage threads synchronization
> > > > > > for Rx/Tx on a given queue.
> > > > > > 
> > > > > > 
> > > > > Yes, in his cover letter, and I contend that notion is an invalid design point.
> > > > > By codifying an area of code as an 'owner', rather than an execution context,
> > > > > you're defining the notion of heirarchy, not ownership. That is to say,
> > > > > you want to codify the notion that there are top level ports that the
> > > > > application might see, and some of those top level ports are parents to
> > > > > subordinate ports, which only the parent port should access directly.  If thats
> > > > > all you want to encode, there are far easier ways to do it:
> > > > > 
> > > > > struct rte_eth_shared_data {
> > > > > 	< existing bits >
> > > > > 	struct rte_eth_port_list {
> > > > > 		struct rte_eth_port_list *children;
> > > > > 		struct rte_eth_port_list *parent;
> > > > > 	};
> > > > > };
> > > > > 
> > > > > 
> > > > > Build an api around a structure like that, so that the parent/child relationship
> > > > > is globally clear, and this would be much easier, especially if you want to
> > > > > continue asserting that the notion of synchronization/exclusion is an exercise
> > > > > left to the application.
> > > > 
> > > > Not only Neil.
> > > > An owner can be something else than a port.
> > > > An owner can be an app process (multi-processes).
> > > > An owner can be a library.
> > > > The intent is really to solve the generic problem of which code
> > > > is managing a port.
> > > > 
> > > I don't see how this precludes any part of what you just said.  Define the
> > > rte_eth_port_list externally to the shared_data struct and allow any object you
> > > want to allocate it, then anything you want to control a heirarchy of ports can
> > > do so without issue, and the structure is far more clear than an opaque id that
> > > carries subtle semantic ordering with it.
> > 
> > Sorry, I don't understand. Please could you rephrase?
> > 
> 
> Sure, I'm saying the fact that you want an owner to be an object
> (library/port/process) rather than strictly an execution context
> (process/thread) doesn't preclude what I'm proposing above.  You can create a
> generic version of the strcture I propose above like so:
> 
> struct rte_obj_heirarchy {
> 	struct rte_obj_heirarchy *children;
> 	struct rte_obj_heirarchy *parent;
> 	void *owner_data; /* optional */
> };
> 
> And embed that structure in any object you would like to give a representative
> heirarchy to, you then have a fairly simple api
> 
> struct rte_obj_heirarchy *heirarchy_alloc();
> bool heirarchy_set(struct rte_obj_heirarchy *parent, struct rte_obj_heirarcy *child)
> void heirarchy_release(struct rte_obj_heirarchy *obj)
> 
> That gives you the privately held list relationship I think you are in part
> looking for (i.e. the ability for a failsafe device to iterate over the ports it
> is in control of), without the awkwardness of the ordinal priority that the
> current implementation imposes.

What is the awkward ordinal priority?
I see you discuss it below. So let's discuss it below.

> In summary, if what you want is ownership in the strictest sense of the word
> (i.e. mutually exclusive access, which I think makes sense), then using a lock
> and flag is really the simplest way to go.  If instead what you want is a
> heirarchical relationship where you can iterate over a limited set of objects
> (the failsafe child port example), then the above is what you want.

We want only ownership. That's why it's called ownership :)
The hierarchical relationship is private to the owner.
For instance, failsafe implements its own list of sub-devices.
So we just need to expose that the ports are already owned.

> The soution Matan is providing does some of each of these things, but comes with
> very odd side effects
> 
> It offers a level of mutual exclusion, in that only one
> object can own another at a time, but does so in a way that introduces this very
> atypical ordinality (once an ownership object is created with owner_new, any
> previously created ownership object will be denied the ability to take ownership
> of a port)

You mean only the last owner id can take an ownership?
If yes, it looks like a bug.
Please could you show what is responsible of this effect in the patch?

> It also offers a level of filtering (in that if you can set the ownership id of
> a given set of object to the value X, you can then iterate over them by
> iterating over all objects of that type, and filtering on their id), but it
> offers no clear in-memory relationship between parent and children (i.e. if you
> were to look at at an object in a debugger and see that it was owned by owner id
> X, it would provide you with no indicator of what object held the allocated
> ownership object assigned id X.

I think it is wrong. There is an owner name for debug/printing purpose.

> My proposal trades a few bytes of data in
> exchage for a global clear, definitive heirarcy relationship.  And if you add an
> api call and a spinlock, you can easily graft on mutual exclusion here, by
> blocking access to objects that arent the immediate parent of a given object.

For the hierarchical relationship, I think it is over-engineered.
For blocking access, it means you need a caller id parameter in every
functions in order to identify if the caller is the owner.

My summary:
- you think there is a bug - needs to show
- you think about relationship needs that I don't see
- you think about access permission which would be a huge change

  reply	other threads:[~2018-01-19 20:19 UTC|newest]

Thread overview: 212+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-28 11:57 [dpdk-dev] [PATCH 0/5] ethdev: Port ownership Matan Azrad
2017-11-28 11:57 ` [dpdk-dev] [PATCH 1/5] ethdev: free a port by a dedicated API Matan Azrad
2017-11-28 11:57 ` [dpdk-dev] [PATCH 2/5] ethdev: add port ownership Matan Azrad
2017-11-30 12:36   ` Neil Horman
2017-11-30 13:24     ` Gaëtan Rivet
2017-11-30 14:30       ` Matan Azrad
2017-11-30 15:09         ` Gaëtan Rivet
2017-11-30 15:43           ` Matan Azrad
2017-12-01 12:09       ` Neil Horman
2017-12-03  8:04         ` Matan Azrad
2017-12-03 11:10           ` Ananyev, Konstantin
2017-12-03 13:46             ` Matan Azrad
2017-12-04 16:01               ` Neil Horman
2017-12-04 18:10                 ` Matan Azrad
2017-12-04 22:30                   ` Neil Horman
2017-12-05  6:08                     ` Matan Azrad
2017-12-05 10:05                       ` Bruce Richardson
2017-12-08 11:35                         ` Thomas Monjalon
2017-12-08 12:31                           ` Neil Horman
2017-12-21 17:06                             ` Thomas Monjalon
2017-12-21 17:43                               ` Neil Horman
2017-12-21 19:37                                 ` Matan Azrad
2017-12-21 20:14                                   ` Neil Horman
2017-12-21 21:57                                     ` Matan Azrad
2017-12-22 14:26                                       ` Neil Horman
2017-12-23 22:36                                         ` Matan Azrad
2017-12-29 16:56                                           ` Neil Horman
2017-12-05 19:26                       ` Neil Horman
2017-12-08 11:06                         ` Thomas Monjalon
2017-12-05 11:12               ` Ananyev, Konstantin
2017-12-05 11:44                 ` Ananyev, Konstantin
2017-12-05 11:53                   ` Thomas Monjalon
2017-12-05 14:56                     ` Bruce Richardson
2017-12-05 14:57                     ` Ananyev, Konstantin
2017-12-05 11:47                 ` Thomas Monjalon
2017-12-05 15:13                   ` Ananyev, Konstantin
2017-12-05 15:49                     ` Thomas Monjalon
2017-11-28 11:57 ` [dpdk-dev] [PATCH 3/5] net/failsafe: free an eth port by a dedicated API Matan Azrad
2017-11-28 11:58 ` [dpdk-dev] [PATCH 4/5] net/failsafe: use ownership mechanism to own ports Matan Azrad
2017-11-28 11:58 ` [dpdk-dev] [PATCH 5/5] app/testpmd: adjust ethdev port ownership Matan Azrad
2018-01-07  9:45 ` [dpdk-dev] [PATCH v2 0/6] ethdev: " Matan Azrad
2018-01-07  9:45   ` [dpdk-dev] [PATCH v2 1/6] ethdev: fix port data reset timing Matan Azrad
2018-01-07  9:45   ` [dpdk-dev] [PATCH v2 2/6] ethdev: add port ownership Matan Azrad
2018-01-10 13:36     ` Ananyev, Konstantin
2018-01-10 16:58       ` Matan Azrad
2018-01-11 12:40         ` Ananyev, Konstantin
2018-01-11 14:51           ` Matan Azrad
2018-01-12  0:02             ` Ananyev, Konstantin
2018-01-12  7:24               ` Matan Azrad
2018-01-15 11:45                 ` Ananyev, Konstantin
2018-01-15 13:09                   ` Matan Azrad
2018-01-15 18:43                     ` Ananyev, Konstantin
2018-01-16  8:04                       ` Matan Azrad
2018-01-16 19:11                         ` Ananyev, Konstantin
2018-01-16 20:32                           ` Matan Azrad
2018-01-17 11:24                             ` Ananyev, Konstantin
2018-01-17 12:05                               ` Matan Azrad
2018-01-17 12:54                                 ` Ananyev, Konstantin
2018-01-17 13:10                                   ` Matan Azrad
2018-01-17 16:52                                     ` Ananyev, Konstantin
2018-01-17 18:02                                       ` Matan Azrad
2018-01-17 20:34                                       ` Matan Azrad
2018-01-18 14:17                                         ` Ananyev, Konstantin
2018-01-18 14:26                                           ` Matan Azrad
2018-01-18 14:41                                             ` Ananyev, Konstantin
2018-01-18 14:45                                               ` Matan Azrad
2018-01-18 14:51                                                 ` Ananyev, Konstantin
2018-01-18 15:00                                                   ` Matan Azrad
2018-01-17 14:00                                 ` Neil Horman
2018-01-17 17:01                                   ` Ananyev, Konstantin
2018-01-18 13:10                                     ` Neil Horman
2018-01-18 14:00                                       ` Matan Azrad
2018-01-18 16:54                                         ` Neil Horman
2018-01-18 17:20                                           ` Matan Azrad
2018-01-18 18:41                                             ` Neil Horman
2018-01-18 20:21                                               ` Matan Azrad
2018-01-19  1:41                                                 ` Neil Horman
2018-01-19  7:14                                                   ` Matan Azrad
2018-01-19  9:30                                                     ` Bruce Richardson
2018-01-19 10:44                                                       ` Matan Azrad
2018-01-19 13:30                                                         ` Neil Horman
2018-01-19 13:57                                                           ` Matan Azrad
2018-01-19 14:13                                                           ` Thomas Monjalon
2018-01-19 15:27                                                             ` Neil Horman
2018-01-19 17:17                                                               ` Thomas Monjalon
2018-01-19 17:43                                                                 ` Neil Horman
2018-01-19 18:12                                                                   ` Thomas Monjalon
2018-01-19 19:47                                                                     ` Neil Horman
2018-01-19 20:19                                                                       ` Thomas Monjalon [this message]
2018-01-19 22:52                                                                         ` Neil Horman
2018-01-20  3:38                                                                         ` Tuxdriver
2018-01-20 12:54                                                                       ` Ananyev, Konstantin
2018-01-20 14:02                                                                         ` Thomas Monjalon
2018-01-19 12:55                                                       ` Neil Horman
2018-01-19 13:52                                                     ` Neil Horman
2018-01-18 16:27                                     ` Neil Horman
2018-01-17 17:58                                   ` Matan Azrad
2018-01-18 13:20                                     ` Neil Horman
2018-01-18 14:52                                       ` Matan Azrad
2018-01-19 13:57                                         ` Neil Horman
2018-01-19 14:07                                           ` Thomas Monjalon
2018-01-19 14:32                                             ` Neil Horman
2018-01-19 17:09                                               ` Thomas Monjalon
2018-01-19 17:37                                                 ` Neil Horman
2018-01-19 18:10                                                   ` Thomas Monjalon
2018-01-21 22:12                                                     ` Ferruh Yigit
2018-01-07  9:45   ` [dpdk-dev] [PATCH v2 3/6] ethdev: synchronize port allocation Matan Azrad
2018-01-07  9:58     ` Matan Azrad
2018-01-07  9:45   ` [dpdk-dev] [PATCH v2 4/6] net/failsafe: free an eth port by a dedicated API Matan Azrad
2018-01-07  9:45   ` [dpdk-dev] [PATCH v2 5/6] net/failsafe: use ownership mechanism to own ports Matan Azrad
2018-01-08 10:32     ` Gaëtan Rivet
2018-01-08 11:16       ` Matan Azrad
2018-01-08 11:35         ` Gaëtan Rivet
2018-01-07  9:45   ` [dpdk-dev] [PATCH v2 6/6] app/testpmd: adjust ethdev port ownership Matan Azrad
2018-01-08 11:39     ` Gaëtan Rivet
2018-01-08 12:30       ` Matan Azrad
2018-01-08 13:30         ` Gaëtan Rivet
2018-01-08 13:55           ` Matan Azrad
2018-01-08 14:21             ` Gaëtan Rivet
2018-01-08 14:42               ` Matan Azrad
2018-01-16  5:53     ` Lu, Wenzhuo
2018-01-16  8:15       ` Matan Azrad
2018-01-17  0:46         ` Lu, Wenzhuo
2018-01-17  8:51           ` Matan Azrad
2018-01-18  0:53             ` Lu, Wenzhuo
2018-01-18 16:35   ` [dpdk-dev] [PATCH v3 0/7] Port ownership and syncronization Matan Azrad
2018-01-18 16:35     ` [dpdk-dev] [PATCH v3 1/7] ethdev: fix port data reset timing Matan Azrad
2018-01-18 17:00       ` Thomas Monjalon
2018-01-19 12:38       ` Ananyev, Konstantin
2018-03-05 11:24       ` [dpdk-dev] [dpdk-stable] " Ferruh Yigit
2018-03-05 14:52         ` Matan Azrad
2018-03-05 15:06           ` Ferruh Yigit
2018-03-05 15:12             ` Matan Azrad
2018-03-27 22:37               ` Ferruh Yigit
2018-03-28 12:07                 ` Matan Azrad
2018-03-30 10:39                   ` Ferruh Yigit
2018-04-19 11:07                     ` Ferruh Yigit
2018-04-25 12:16                       ` Matan Azrad
2018-04-25 12:30                         ` Ori Kam
2018-04-25 12:54                         ` Ferruh Yigit
2018-04-25 14:01                           ` Matan Azrad
2018-01-18 16:35     ` [dpdk-dev] [PATCH v3 2/7] ethdev: fix used portid allocation Matan Azrad
2018-01-18 17:00       ` Thomas Monjalon
2018-01-19 12:40       ` Ananyev, Konstantin
2018-01-20 16:48         ` Matan Azrad
2018-01-20 17:26           ` Ananyev, Konstantin
2018-01-18 16:35     ` [dpdk-dev] [PATCH v3 3/7] ethdev: add port ownership Matan Azrad
2018-01-18 21:11       ` Thomas Monjalon
2018-01-19 12:41       ` Ananyev, Konstantin
2018-01-18 16:35     ` [dpdk-dev] [PATCH v3 4/7] ethdev: synchronize port allocation Matan Azrad
2018-01-18 20:43       ` Thomas Monjalon
2018-01-18 20:52         ` Matan Azrad
2018-01-18 21:17           ` Thomas Monjalon
2018-01-19 12:47       ` Ananyev, Konstantin
2018-01-18 16:35     ` [dpdk-dev] [PATCH v3 5/7] net/failsafe: free an eth port by a dedicated API Matan Azrad
2018-01-18 16:35     ` [dpdk-dev] [PATCH v3 6/7] net/failsafe: use ownership mechanism to own ports Matan Azrad
2018-01-18 16:35     ` [dpdk-dev] [PATCH v3 7/7] app/testpmd: adjust ethdev port ownership Matan Azrad
2018-01-19 12:37       ` Ananyev, Konstantin
2018-01-19 12:51         ` Matan Azrad
2018-01-19 13:08           ` Ananyev, Konstantin
2018-01-19 13:35             ` Matan Azrad
2018-01-19 15:00               ` Gaëtan Rivet
2018-01-20 18:14                 ` Matan Azrad
2018-01-22 10:17                   ` Gaëtan Rivet
2018-01-22 11:22                     ` Matan Azrad
2018-01-22 12:28                 ` Ananyev, Konstantin
2018-01-22 13:22                   ` Matan Azrad
2018-01-22 20:48                     ` Ananyev, Konstantin
2018-01-23  8:54                       ` Matan Azrad
2018-01-23 12:56                         ` Gaëtan Rivet
2018-01-23 14:30                           ` Matan Azrad
2018-01-25  9:36                             ` Matan Azrad
2018-01-25 10:05                               ` Thomas Monjalon
2018-01-25 11:15                                 ` Ananyev, Konstantin
2018-01-25 11:33                                   ` Thomas Monjalon
2018-01-25 11:55                                     ` Ananyev, Konstantin
2018-01-23 13:34                         ` Ananyev, Konstantin
2018-01-23 14:18                           ` Thomas Monjalon
2018-01-23 15:12                             ` Ananyev, Konstantin
2018-01-23 15:18                               ` Ananyev, Konstantin
2018-01-23 17:33                                 ` Thomas Monjalon
2018-01-23 21:18                                   ` Ananyev, Konstantin
2018-01-24  8:10                                     ` Thomas Monjalon
2018-01-24 18:30                                       ` Ananyev, Konstantin
2018-01-25 10:55                                         ` Thomas Monjalon
2018-01-25 11:09                                           ` Ananyev, Konstantin
2018-01-25 11:27                                             ` Thomas Monjalon
2018-01-23 14:43                           ` Matan Azrad
2018-01-20 21:24     ` [dpdk-dev] [PATCH v4 0/7] Port ownership and syncronization Matan Azrad
2018-01-20 21:24       ` [dpdk-dev] [PATCH v4 1/7] ethdev: fix port data reset timing Matan Azrad
2018-01-20 21:24       ` [dpdk-dev] [PATCH v4 2/7] ethdev: fix used portid allocation Matan Azrad
2018-01-20 21:24       ` [dpdk-dev] [PATCH v4 3/7] ethdev: add port ownership Matan Azrad
2018-01-21 20:43         ` Ferruh Yigit
2018-01-21 20:46         ` Ferruh Yigit
2018-01-20 21:24       ` [dpdk-dev] [PATCH v4 4/7] ethdev: synchronize port allocation Matan Azrad
2018-01-20 21:24       ` [dpdk-dev] [PATCH v4 5/7] net/failsafe: free an eth port by a dedicated API Matan Azrad
2018-01-20 21:24       ` [dpdk-dev] [PATCH v4 6/7] net/failsafe: use ownership mechanism to own ports Matan Azrad
2018-01-20 21:24       ` [dpdk-dev] [PATCH v4 7/7] app/testpmd: adjust ethdev port ownership Matan Azrad
2018-01-22 16:38       ` [dpdk-dev] [PATCH v5 0/7] Port ownership and synchronization Matan Azrad
2018-01-22 16:38         ` [dpdk-dev] [PATCH v5 1/7] ethdev: fix port data reset timing Matan Azrad
2018-01-22 16:38         ` [dpdk-dev] [PATCH v5 2/7] ethdev: fix used portid allocation Matan Azrad
2018-01-22 16:38         ` [dpdk-dev] [PATCH v5 3/7] ethdev: add port ownership Matan Azrad
2018-01-22 16:38         ` [dpdk-dev] [PATCH v5 4/7] ethdev: synchronize port allocation Matan Azrad
2018-01-22 16:38         ` [dpdk-dev] [PATCH v5 5/7] net/failsafe: free an eth port by a dedicated API Matan Azrad
2018-01-22 16:38         ` [dpdk-dev] [PATCH v5 6/7] net/failsafe: use ownership mechanism to own ports Matan Azrad
2018-01-22 16:38         ` [dpdk-dev] [PATCH v5 7/7] app/testpmd: adjust ethdev port ownership Matan Azrad
2018-01-25  1:47           ` Lu, Wenzhuo
2018-01-25  8:30             ` Matan Azrad
2018-01-26  0:50               ` Lu, Wenzhuo
2018-01-29 11:21         ` [dpdk-dev] [PATCH v5 0/7] Port ownership and synchronization Matan Azrad
2018-01-31 19:53           ` Thomas Monjalon
2018-01-25 14:35     ` [dpdk-dev] [PATCH v3 0/7] Port ownership and syncronization Ferruh Yigit

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