[dpdk-dev] [PATCH] lib: change rte_ring dequeue to guarantee ordering before tail update

Thomas Monjalon thomas.monjalon at 6wind.com
Sat Jul 23 11:02:33 CEST 2016


2016-07-23 8:05 GMT+02:00 Jerin Jacob <jerin.jacob at caviumnetworks.com>:
> On Thu, Jul 21, 2016 at 11:26:50PM +0200, Thomas Monjalon wrote:
>> > > Consumer queue dequeuing must be guaranteed to be done fully before the tail is updated. This is not guaranteed with a read barrier,
>> > > changed to a write barrier just before tail update which in practice guarantees correct order of reads and writes.
>> > >
>> > > Signed-off-by: Juhamatti Kuusisaari <juhamatti.kuusisaari at coriant.com>
>> >
>> > Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
>>
>> Applied, thanks
>
> There was ongoing discussion on this
> http://dpdk.org/ml/archives/dev/2016-July/044168.html

Sorry Jerin, I forgot this email.
The problem is that nobody replied to your email and you did not nack
the v2 of this patch.

> This change may not be required as it has the performance impact.

We need to clearly understand what is the performance impact
(numbers and use cases) on one hand, and is there a real bug fixed
by this patch on the other hand?

Please guys make things clear and we'll revert if needed.


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