On Wed, Oct 08, 2014 at 02:11:34PM +0000, Pattan, Reshma wrote: > > > > -----Original Message----- > > From: Neil Horman [mailto:nhorman at tuxdriver.com] > > Sent: Tuesday, October 7, 2014 12:22 PM > > To: Pattan, Reshma > > Cc: dev at dpdk.org > > Subject: Re: [dpdk-dev] [PATCH RFC] librte_reorder: new reorder library > > > > On Tue, Oct 07, 2014 at 09:33:06AM +0000, Pattan, Reshma wrote: > > > Hi All, > > > > > > I am planning to implement packet reorder library. Details are as below, > > please go through them and provide the comments. > > > > > > Requirement: > > > To reorder out of ordered packets that are received from > > > different > > cores. > > > > > > Usage: > > > To be used along with distributor library. Next version of distributor are > > planned to distribute incoming packets to all worker cores irrespective of > > the > > flow type. > > > In this case to ensure in order delivery of the packets at output side > > > reorder > > library will used by the tx end. > > > > > > Assumption: > > > All input packets will be marked with sequence number in seqn field of > > > mbuf, > > this will be the reference for reordering at the tx end. > > > Sequence number will be of type uint32_t. New sequence number field seqn > > will be added to mbuf structure. > > > > > > Design: > > > a)There will be reorder buffer(circular buffer) structure maintained in > > > reorder > > library to store reordered packets and other details of buffer like head to > > drain > > the packet from, min sequence number and other details. > > > b)Library will provide insert and drain functions to > > > reorder and fetch > > out the reordered packets respectively. > > > c)Users of library should pass the packets to insert functions for > > > reordering. > > > > > > Insertion logic: > > > Sequence number of current packet will be used to calculate offset in > > > reorder > > buffer and write packet to the location in the reorder buffer > > corresponding to > > offset. > > > Offset is calculated as difference of > > > current packet sequence > > number and sequence number associated with reorder buffer. > > > > > > During sequence number wrapping or wrapping over of reorder buffer size, > > before inserting the new packet we should move offset number of packets to > > other buffer called overflow buffer and advance the head of reorder buffer > > by > > "offset-reorder buffer size" and insert the new packet. > > > > > > Insert function: > > > int rte_reorder_insert(struct rte_reorder_buffer *buffer, struct > > > rte_mbuf *mbuf); > > > Note: Other insert function is also under plan to insert burst of packets. > > > > > > Reorder buffer: > > > struct rte_reorder_buffer { > > > unsigned int size; /* The size (number of entries) of the > > > buffer. */ > > > unsigned int mask; /* Mask (size - 1) of the buffer */ > > > unsigned int head; /* Current head of buffer */ > > > uint32_t min_seqn; /* latest sequence number associated with > > > buffer > > */ > > > struct rte_mbuf *entries[MAX_REORDER_BUFFER_SIZE]; /* buffer > > > to hold reordered mbufs */ }; > > > > > > d)Users can fetch out the reordered packets by drain function provided by > > library. Users must pass the mbuf array , drain function should fill > > passed mbuff > > array with the reordered buffer packets. > > > During drain operation, overflow buffer packets will be fetched out > > > first and > > then reorder buffer. > > > > > > Drain function: > > > int rte_reorder_drain(struct rte_reorder_buffer > > > *buffer, struct rte_mbuf **mbufs) > > > > > > Thanks, > > > Reshma > > > > > > > This seems reasonable, but why not integrate it with the distributor > > library rather > > than create a separate library for it? It seems as though the distributor > > library is > > a pre-requisite for this libraries use anyway, as otherwise there will not > > be > > anything to reorder Neil > > > > Hi Neil, > > Reorder library should be standalone , as there are many ways that can cause > out of ordering of packets, I just mentioned future packet distributor > enhancements > as one of the example for out of ordering. > Other ways like, users can directly distribute the packets to different cores > via rings and that causes packet out of ordering as well. > So, keeping reorder library standalone would be good to work with all packet > distribution ways. >
Hmm, ok, that seems reasonable. Just out of curiosity, where do you intend to inject the packet sequence number for this library? Neil
