> -----Original Message----- > From: Ahmed Mansour [mailto:ahmed.mans...@nxp.com] > Sent: Saturday, February 24, 2018 1:17 AM > To: Trahe, Fiona <fiona.tr...@intel.com>; dev@dpdk.org; > shally.ve...@cavium.com > Cc: De Lara Guarch, Pablo <pablo.de.lara.gua...@intel.com>; Athreya, Narayana > Prasad > <narayanaprasad.athr...@cavium.com>; Gupta, Ashish <ashish.gu...@cavium.com>; > Sahu, Sunila > <sunila.s...@cavium.com>; Challa, Mahipal <mahipal.cha...@cavium.com>; Jain, > Deepak K > <deepak.k.j...@intel.com>; Hemant Agrawal <hemant.agra...@nxp.com>; Roy Pledge > <roy.ple...@nxp.com>; Youri Querry <youri.querr...@nxp.com> > Subject: Re: [dpdk-dev] [PATCH] compressdev: implement API > > Hi Fiona, > > Thanks for starting this discussion. In the current API the user must > make 12 API calls just to get information to compress. Maybe there is a > way to simplify. At least for some use cases (stateless). I think a call > sometime next week would be good to help clarify coalesce some of the > complexity. [Fiona] Would 10:30 GMT on Wednesday 28th Feb suit? > > I added specific comments inline. > > Thanks, > > Ahmed > > On 2/21/2018 2:12 PM, Trahe, Fiona wrote: > > We've been struggling with the idea of session in compressdev. > > > > Is it really a session? > > - It's not in the same sense as cryptodev where it's used to hold a key, > > and maps to a Security > Association. > > - It's a set of immutable data that is needed with the op and stream to > > perform the operation. > > - It inherited from cryptodev the ability to be set up for multiple driver > > types and used across any > > devices of those types. For stateful ops this facility can't be used. > > For stateless we don't think it's important, and think it's unlikely to > > be used. > > - Drivers use it to prepare private data, set up resources, do pre-work, > > so there's > > less work to be done on the data path. Initially we didn't have a > > stream, we do now, > > this may be a better alternative place for that work. > > So we've been toying with the idea of getting rid of the session. > [Ahmed] In our proprietary API the stream and session are one. A session > holds many properties like the op-type, instead of having this > information in the op itself. This way we lower the per op setup cost. > This also allows rapid reuse of stateful infrastructure, once a stream > is closed on a stateful session, the next op (stream) on this session > reuses the stateful storage. Obviously if a stream is in "pause mode" on > a session, all following ops that may be unrelated to this > stream/session must also wait until this current stream is closed or > aborted before the infrastructure can be reused. > > > > We also struggle with the idea of setting up a stream for stateless ops. > > - Well, really I just think the name is misleading, i.e. there's no > > problem with setting > > up some private PMD data to use with stateless operations, just calling > > it a > > stream doesn't seem right. > [Ahmed] I agree. The op has all the necessary information to process it > in the current API? Both the stream and the op are one time use. We > can't attach multiple similar ops to a single stream/session and rely on > their properties to simplify op setup, so why the hassle. > > > > So putting above thoughts together I want to propose: > > - Removal of the session and all associated APIs. > > - Passing in one of three data types in the rte_comp_op > > > > union { > > struct rte_comp_xform *xform; > > /**< Immutable compress/decompress params */ > > void *pmd_stateless_data; > > /**< Stateless private PMD data derived from an rte_comp_xform > > * rte_comp_stateless_data_init() must be called on a device > > * before sending any STATELESS operations. If the PMD returns a > > non-NULL > > * value the handle must be attached to subsequent STATELESS > > operations. > > * If a PMD returns NULL, then the xform should be passed directly > > to each op > > */ > > void *stream; > > /* Private PMD data derived initially from an rte_comp_xform, which > > holds state > > * and history data and evolves as operations are processed. > > * rte_comp_stream_create() must be called on a device for all > > STATEFUL > > * data streams and the resulting stream attached > > * to the one or more operations associated with the data stream. > > * All operations in a stream must be sent to the same device. > > */ > > } > [Ahmed] I like this setup, but I am not sure in what cases the xform > immutable would be used. I understand the other two. [Fiona] The xform is there because I don't know yet what limitations may apply to the pmd_stateless_data. If it has no limitation and once set up once on a device can be attached simultaneously to any op sent to any qp on that device then we don't need the xform. But I understood from Shally's earlier request for setting up a stream on a stateless request that some resources are allocated, so we may need to document some limitations. In this case the xform may be a better path for PMDs which don't have the same limitations.
> > Notes: > > 1. Internally if a PMD wants to use the exact same data structure for both > > it can do, > > just on the API I think it's better if they're named differently with > > different comments. > > 2. I'm not clear of the constraints if any, which attach to the > > pmd_stateless_data > > For our PMD it would only hold immutable data as the session did, and > > so > > could be attached to many ops in parallel. > > Is this true for all PMDs or are there constraints which should be > > called out? > > Is it limited to a specific device, qp, or to be used on one op at a > > time? > > 3. Am open to other naming suggestions, just trying to capture the essence > > of these data structs better than our current API does. > > > > We would put some more helper fns and structure around the above code if > > people > > are in agreement, just want to see if the concept flies before going > > further? > > > > Fiona > > > > > >
