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From: Thomas Monjalon <thomas@monjalon.net>
To: "Morten Brørup" <mb@smartsharesystems.com>,
	"Bruce Richardson" <bruce.richardson@intel.com>
Cc: dev@dpdk.org, olivier.matz@6wind.com,
	andrew.rybchenko@oktetlabs.ru, honnappa.nagarahalli@arm.com,
	konstantin.ananyev@intel.com, ferruh.yigit@intel.com,
	jerinj@marvell.com, gakhil@marvell.com,
	david.marchand@redhat.com
Subject: Re: [dpdk-dev] [PATCH] parray: introduce internal API for dynamic arrays
Date: Tue, 15 Jun 2021 11:28:16 +0200	[thread overview]
Message-ID: <3350188.y60jeB2voQ@thomas> (raw)
In-Reply-To: <YMhofeCvcshdauky@bricha3-MOBL.ger.corp.intel.com>

15/06/2021 10:44, Bruce Richardson:
> On Tue, Jun 15, 2021 at 09:53:33AM +0200, Morten Brørup wrote:
> > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> > > Sent: Tuesday, 15 June 2021 08.48
> > > 
> > > 14/06/2021 17:48, Morten Brørup:
> > > > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas
> > > Monjalon
> > > > It would be much simpler to just increase RTE_MAX_ETHPORTS to
> > > something big enough to hold a sufficiently large array. And possibly
> > > add an rte_max_ethports variable to indicate the number of populated
> > > entries in the array, for use when iterating over the array.
> > > >
> > > > Can we come up with another example than RTE_MAX_ETHPORTS where this
> > > library provides a better benefit?
> > > 
> > > What is big enough?
> > > Is 640KB enough for RAM? ;)
> > 
> > Good point!
> > 
> > I think we agree that:
> > - The cost of this library is some added complexity, i.e. working with a dynamically sized array through a library instead of just indexing into a compile time fixed size array.
> > - The main benefit of this library is saving some RAM (and still allowing a potentially very high number of ports.)
> > 
> > My point was: The amount of RAM we are saving is a key parameter for the cost/benefit analysis. And since I don't think the rte_eth_devices[] array uses a significant amount of memory, I was asking for some other array using more memory, where the cost/benefit analysis would come out more advantageous to your proposed parray library.
> > 
> > > 
> > > When dealing with microservices switching, the numbers can increase
> > > very fast.
> > 
> > Yes, I strongly supported increasing the port_id type from 8 to 16 bits for this reason, when it was discussed at the DPDK Userspace a few years ago in Dublin. And with large RTE_MAX_QUEUES_PER_PORT values, the rte_eth_dev structure uses quite a lot of space for the rx/tx callback arrays. But the memory usage of rte_eth_devices[] is still relatively insignificant in a system wide context.
> > 
> > If main purpose is to optimize the rte_eth_devices[] array, I think there are better alternatives than this library. Bruce and Konstantin already threw a few ideas on the table.
> >
> 
> Yes, though I think we need to be clear on what problems we are trying to
> solve here. A generic resizable array may be a useful library for DPDK in
> its own right, but for the ethdev (and other devs) arrays I think my
> understanding of the problem is that we want:
> 
> * scalability of ethdevs list to large numbers of ports, e.g. 2k
> * while not paying a large memory footprint penalty for those apps which
>   only need a small number of ports, e.g. 2 or 4.
> 
> Is that a fair summary?

Yes.

We must take into account two related issues:
	- the app and libs could allocate some data per device,
increasing the bill.
	- per-device allocation may be more efficient
if allocated on the NUMA node of the device



  reply	other threads:[~2021-06-15  9:28 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-14 10:58 Thomas Monjalon
2021-06-14 12:22 ` Morten Brørup
2021-06-14 13:15   ` Bruce Richardson
2021-06-14 13:32     ` Thomas Monjalon
2021-06-14 14:59       ` Ananyev, Konstantin
2021-06-14 15:48         ` Jerin Jacob
2021-06-15  6:52           ` Thomas Monjalon
2021-06-15  8:00             ` Jerin Jacob
2021-06-15  9:18               ` Thomas Monjalon
2021-06-15  9:33             ` Ananyev, Konstantin
2021-06-15  9:50               ` Thomas Monjalon
2021-06-15 10:08                 ` Ananyev, Konstantin
2021-06-15 14:02                   ` Thomas Monjalon
2021-06-15 14:37                     ` Honnappa Nagarahalli
2021-06-14 15:54         ` Ananyev, Konstantin
2021-06-17 13:08           ` Ferruh Yigit
2021-06-17 14:58             ` Ananyev, Konstantin
2021-06-17 15:17               ` Morten Brørup
2021-06-17 16:12                 ` Ferruh Yigit
2021-06-17 16:55                   ` Morten Brørup
2021-06-18 10:21                     ` Ferruh Yigit
2021-06-17 17:05                   ` Ananyev, Konstantin
2021-06-18  9:14                     ` Morten Brørup
2021-06-18 10:47                       ` Ferruh Yigit
2021-06-18 11:16                         ` Morten Brørup
2021-06-18 10:28                     ` Ferruh Yigit
2021-06-17 15:44               ` Ferruh Yigit
2021-06-18 10:41                 ` Ananyev, Konstantin
2021-06-18 10:49                   ` Ferruh Yigit
2021-06-21 11:06                   ` Ananyev, Konstantin
2021-06-21 12:10                     ` Morten Brørup
2021-06-21 12:30                       ` Ananyev, Konstantin
2021-06-21 13:28                         ` Morten Brørup
     [not found]                           ` <DM6PR11MB4491D4F6FAFDD6E8EEC2A78F9A099@DM6PR11MB4491.namprd11.prod.outlook .com>
2021-06-22  8:33                           ` Ananyev, Konstantin
2021-06-22 10:01                             ` Morten Brørup
2021-06-22 12:13                               ` Ananyev, Konstantin
2021-06-22 13:18                                 ` Morten Brørup
2021-06-21 14:10                         ` Ferruh Yigit
2021-06-21 14:38                           ` Ananyev, Konstantin
2021-06-21 15:56                             ` Ferruh Yigit
2021-06-21 18:17                               ` Ananyev, Konstantin
2021-06-21 14:05                     ` Ferruh Yigit
2021-06-21 14:42                       ` Ananyev, Konstantin
2021-06-21 15:32                         ` Ferruh Yigit
2021-06-21 15:37                           ` Ananyev, Konstantin
2021-06-14 15:48       ` Morten Brørup
2021-06-15  6:48         ` Thomas Monjalon
2021-06-15  7:53           ` Morten Brørup
2021-06-15  8:44             ` Bruce Richardson
2021-06-15  9:28               ` Thomas Monjalon [this message]
2021-06-16  9:42           ` Jerin Jacob
2021-06-16 11:27             ` Morten Brørup
2021-06-16 12:00               ` Jerin Jacob
2021-06-16 13:02               ` Bruce Richardson
2021-06-16 15:01                 ` Morten Brørup
2021-06-16 17:40                   ` Bruce Richardson
2021-06-16 12:22             ` Burakov, Anatoly
2021-06-16 12:59               ` Jerin Jacob
2021-06-16 22:58                 ` Dmitry Kozlyuk
2021-06-14 13:28   ` Thomas Monjalon
2021-06-16 11:11 ` Burakov, Anatoly

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