patches for DPDK stable branches
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From: David Marchand <>
To: "Song, Keesang" <>,
	"" <>,
	 "" <>
Cc: Thomas Monjalon <>,
	"" <>,
	 "" <>,
	"" <>,
	 "" <>,
	 "" <>,
	 "" <>,
	"" <>,
	 "Grimm, Jon" <>,
	"Hollingsworth, Brent" <>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH 0/4] Extend --lcores to run on cores > RTE_MAX_LCORE
Date: Fri, 21 Feb 2020 10:40:09 +0100
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, Feb 21, 2020 at 9:19 AM Song, Keesang <> 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: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2019-12-02 15:41 ` [dpdk-stable] [PATCH 1/4] eal/windows: fix cpuset macro name David Marchand
     [not found] ` <2076701.vBoWY3egPC@xps>
2020-02-21  8:04   ` [dpdk-stable] [dpdk-dev] [PATCH 0/4] Extend --lcores to run on cores > RTE_MAX_LCORE 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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