DPDK patches and discussions
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From: David Marchand <david.marchand@redhat.com>
To: "Song, Keesang" <Keesang.Song@amd.com>,
	"ktraynor@redhat.com" <ktraynor@redhat.com>,
	 "bluca@debian.org" <bluca@debian.org>
Cc: Thomas Monjalon <thomas@monjalon.net>,
	"dev@dpdk.org" <dev@dpdk.org>,
	 "aconole@redhat.com" <aconole@redhat.com>,
	"ferruh.yigit@intel.com" <ferruh.yigit@intel.com>,
	 "bruce.richardson@intel.com" <bruce.richardson@intel.com>,
	 "honnappa.nagarahalli@arm.com" <honnappa.nagarahalli@arm.com>,
	 "drc@linux.vnet.ibm.com" <drc@linux.vnet.ibm.com>,
	"stable@dpdk.org" <stable@dpdk.org>,
	 "Grimm, Jon" <Jon.Grimm@amd.com>,
	"Hollingsworth, Brent" <brent.hollingsworth@amd.com>
Subject: Re: [dpdk-dev] [PATCH 0/4] Extend --lcores to run on cores > RTE_MAX_LCORE
Date: Fri, 21 Feb 2020 10:40:09 +0100	[thread overview]
Message-ID: <CAJFAV8xNp2LsStZ279iUydOd2Zbzj25ghrYDdnzPW54WTq8ayA@mail.gmail.com> (raw)
In-Reply-To: <BYAPR12MB3607ED35C4D85F1F6AF2A83B96120@BYAPR12MB3607.namprd12.prod.outlook.com>

On Fri, Feb 21, 2020 at 9:19 AM Song, Keesang <Keesang.Song@amd.com> wrote:
> [AMD Official Use Only - Internal Distribution Only]

Please, get this header removed.
This is a public mailing list.

> Thanks Thomas for bringing this up.
> I consider this is not a new feature, but rather a fix to address the issue with statically assigned maximum lcore limit on high-density CPU platform such as AMD Epyc.
> As I see a lot of DPDK adopters are still using LTS 18.11 & 19.11, and they have 1~2 yrs of lifetime left, we like to backport this to LTS 18.11 & 19.11 at least.

It is not a fix.

The use of static arrays is a design choice that goes back to the
early days in dpdk.
The addition of --lcores came in after this, but it was introduced for
a different use case than placing lcores on any physical core.
And there was no claim that a core > RTE_MAX_LCORE would be usable.

When testing on a new hardware, it is normal to observe some limitations.
Running DPDK on those platforms should be possible: "should be"
because I do not have access to this hardware and saw neither tests
reports nor performance numbers.
Before this patch, the limitation is that on Epyc, cores >
RTE_MAX_LCORE are not usable.

Now, this change is quite constrained.
If we backport it, I don't expect issues in the main dpdk components
(based on code review and ovs tests with a RTE_MAX_LCORE set to 16 on
a 24 cores system).
There might be issues in some examples or not widely used library
which uses a physical core id instead of a lcore id.

This is the same recurring question "do we allow new features in a
stable branch?".

David Marchand

  reply	other threads:[~2020-02-21  9:40 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-02 15:35 David Marchand
2019-12-02 15:41 ` [dpdk-dev] [PATCH 1/4] eal/windows: fix cpuset macro name David Marchand
2019-12-02 15:42 ` [dpdk-dev] [PATCH 2/4] eal: do not cache lcore detection state David Marchand
2019-12-02 15:42 ` [dpdk-dev] [PATCH 3/4] eal: display all detected cores at startup David Marchand
2019-12-02 15:42 ` [dpdk-dev] [PATCH 4/4] eal: remove limitation on cpuset with --lcores David Marchand
2020-01-14 12:58 ` [dpdk-dev] [PATCH 0/4] Extend --lcores to run on cores > RTE_MAX_LCORE David Marchand
2020-01-14 15:32   ` [dpdk-dev] [PATCH 0/4] Extend --lcores to run on cores >RTE_MAX_LCORE Morten Brørup
2020-01-20 18:37 ` [dpdk-dev] [PATCH 0/4] Extend --lcores to run on cores > RTE_MAX_LCORE Yigit, Ferruh
2020-01-20 19:35   ` David Marchand
2020-01-21  0:24 ` Thomas Monjalon
2020-02-21  8:04   ` Thomas Monjalon
2020-02-21  8:19     ` Song, Keesang
2020-02-21  9:40       ` David Marchand [this message]
2020-02-21 14:48         ` Aaron Conole
2020-02-21 16:38           ` Stephen Hemminger
2020-05-29  3:05     ` Song, Keesang
2020-05-29  3:05       ` Song, Keesang
2020-06-01 21:22         ` Thomas Monjalon
2020-06-01 22:54           ` Song, Keesang
2020-06-09 16:30             ` Song, Keesang
2020-06-09 17:48               ` Luca Boccassi
2020-06-09 21:34                 ` Kevin Traynor

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