Re: [dpdk-dev] [PATCH RFC] librte_reorder: new reorder library

[Matthew Hall <mhall@mhcomputing.net>]

On Fri, Oct 17, 2014 at 09:44:49AM +0000, Pattan, Reshma wrote:
> [Reshma]: Library just takes care of packets what it has got. No waiting 
> mechanism is used for missing packets.

> [Reshma]: This is dependent upon how frequently packets are enqueued and 
> dequeued from it. Packets which are in order and without gaps are dequeued 
> at the next call to the dequeue api. If there is a gap, the time taken to 
> skip over the gap will depend on the size of the reorder ring.

I am not sure this library will help much if it can't handle missing / delayed 
packets in some way.

When you're using a non-flow-aware distributor and moving packets around 
randomly / round robin / not using flows, you'll end up with some cases where 
a packet has some HOL blocking in some core and another later packet comes 
through faster on another core.

Maybe I missed something here, but I think there's got to be some logic where 
you can tell it's not ready to dequeue something yet, because there's a gap it 
needs to fill, or flows will break a lot due to race conditions I suspect.

Matthew.