From mboxrd@z Thu Jan  1 00:00:00 1970
From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Subject: Re: [PATCH v4 2/2] ring: move the atomic load of head
	above the loop
Date: Fri, 2 Nov 2018 04:30:36 +0000
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Cc: "dev@dpdk.org" <dev@dpdk.org>, "thomas@monjalon.net"
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To: "Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>, Stephen Hemminger
 <stephen@networkplumber.org>
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<Fixing this to make the reply inline, making email plain text>

=A0
On Thu, 1 Nov 2018 17:53:51 +0800=20
Gavin Hu <mailto:gavin.hu@arm.com> wrote:=20

> +* **Updated the ring library with C11 memory model.**=20
> +=20
> + Updated the ring library with C11 memory model including the following =
changes:=20
> +=20
> + * Synchronize the load and store of the tail=20
> + * Move the atomic load of head above the loop=20
> +=20

Does this really need to be in the release notes? Is it a user visible chan=
ge=20
or just an internal/optimization and fix.=20

[Gavin] There is no api changes, but this is a significant change as ring i=
s fundamental and widely used, it decreases latency by 25% in our tests, it=
 may do even better for cases with more contending producers/consumers or d=
eeper depth of rings.

[Honnappa] I agree with Stephen. Release notes should be written from DPDK =
user perspective. In the rte_ring case, the user has the option of choosing=
 between c11 and non-c11 algorithms. Performance would be one of the criter=
ia to choose between these 2 algorithms. IMO, it probably makes sense to in=
dicate that the performance of c11 based algorithm has been improved. Howev=
er, I do not know what DPDK has followed historically regarding performance=
 optimizations. I would prefer to follow whatever has been followed so far.
I do not think that we need to document the details of the internal changes=
 since it does not help the user make a decision.