> -----Original Message----- > From: Jerin Jacob [mailto:jerin.ja...@caviumnetworks.com] > Sent: Monday, October 30, 2017 12:38 PM > To: Eads, Gage <gage.e...@intel.com> > Cc: dev@dpdk.org; Richardson, Bruce <bruce.richard...@intel.com>; Van > Haaren, Harry <harry.van.haa...@intel.com>; Hemant Agrawal > <hemant.agra...@nxp.com>; Nipun Gupta <nipun.gu...@nxp.com>; Rao, > Nikhil <nikhil....@intel.com>; Pavan Nikhilesh > <pbhagavat...@caviumnetworks.com>; Thomas Monjalon > <tho...@monjalon.net> > Subject: Re: [dpdk-dev] [PATCH] eventdev: remove experimental label > > -----Original Message----- > > Date: Mon, 23 Oct 2017 18:27:52 +0000 > > From: "Eads, Gage" <gage.e...@intel.com> > > To: Jerin Jacob <jerin.ja...@caviumnetworks.com>, "dev@dpdk.org" > > <dev@dpdk.org> > > CC: "Richardson, Bruce" <bruce.richard...@intel.com>, "Van Haaren, Harry" > > <harry.van.haa...@intel.com>, Hemant Agrawal > > <hemant.agra...@nxp.com>, Nipun Gupta <nipun.gu...@nxp.com>, "Rao, > > Nikhil" <nikhil....@intel.com>, Pavan Nikhilesh > > <pbhagavat...@caviumnetworks.com>, Thomas Monjalon > > <tho...@monjalon.net> > > Subject: RE: [dpdk-dev] [PATCH] eventdev: remove experimental label > > > > Hi Jerin, > > Hi Gage, > > > > > I have one concern with the API that may delay changing the label. > > > > The implicit release that in rte_event_dequeue_burst() is a problem when > > using > asynchronous/look-aside hardware, like a cryptodev. For instance, let's say in > pipeline stage N the worker takes the event's mbuf and places it in a > per-worker > crypto request queue. When the worker next calls rte_event_dequeue_burst(), > that function will release the previous event which could cause the flow to > migrate to another worker, and this could result in packet reordering. > > > > To prevent this, the worker can't call dequeue until the look-aside > > operation > completes...in effect treating the asynchronous/look-aside hardware as > synchronous. Another option is to feed stage N's queue to a single port to > avoid > the flow migration, but that port may become a bottleneck. > > > > We could remove the implicit release functionality or add a port > > configuration > flag to disable it, so the default behavior is unchanged. Removing it will > completely will likely require changes in existing code, but it simplifies > the usage > model (all dequeued events must be either forwarded or released) and the > PMD's dequeue code. This functionality could be removed from the software > eventdev fairly easily, but I haven't looked into the hardware PMDs. > > > > The HW implementations, I know, it does the implicit release. Otherwise it > will result in deadlock because it cannot hold reordering metadata for > the longtime(SRAM is limited etc) > > Coming back to cryptodev use case, if I understand it correctly, before > application enqueues to crypto queue, the application will change the tag and > submit to ATOMIC queue. So as long as crypto queue competes for the > crypto work in order then the order will be maintained. > > In typical outbound IPSec use case, > - Stage 1 will be processed in ORDERED where application does the SA > lookup > - Once SA found, application enqueue to ATOMIC stage with SA as flow_id. > - When the event comes from the ATOMIC queue, it in ingress order and > then it submits to the crypto queue > - Crypto queue maintains the FIFO order. > - On IPSec crypto work competition, packets will come in Stage 3. > - So at Stage 3, packets are in ingress order for the given SA flow id. > ^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > Having said that, If SW implementation needs to do differently for performance > reasons then we will end up in capability as HW implementation works in the > implicit release. May we can sort out through capability or separate adapter > for > crypto case. But I think, those will be new additions to the API.So removing > the > experimental tags may be OK. > But if you have strong opinion on keeping the experimental tag till we address > the crypto use case then I am fine with that. > > Thoughts?
Ok, agreed, no need to keep the tag for this concern. The capability idea is intriguing -- I'll chew on this and we can tackle it at a later point. Thanks, Gage > > Jerin > > > > > > Thanks, > > Gage > >
