>-----Original Message----- >From: Trahe, Fiona [mailto:[email protected]] >Sent: 13 March 2018 21:22 >To: Verma, Shally <[email protected]>; Ahmed Mansour ><[email protected]>; [email protected] >Cc: De Lara Guarch, Pablo <[email protected]>; Athreya, Narayana >Prasad <[email protected]>; >Gupta, Ashish <[email protected]>; Sahu, Sunila ><[email protected]>; Challa, Mahipal ><[email protected]>; Jain, Deepak K <[email protected]>; Hemant >Agrawal <[email protected]>; Roy >Pledge <[email protected]>; Youri Querry <[email protected]>; Daly, Lee ><[email protected]>; Jozwiak, TomaszX ><[email protected]>; Trahe, Fiona <[email protected]> >Subject: RE: [dpdk-dev] [PATCH] compressdev: implement API - mbuf alternative > >Hi Shally, > >> -----Original Message----- >> From: Verma, Shally [mailto:[email protected]] >> Sent: Tuesday, March 13, 2018 8:15 AM >> To: Trahe, Fiona <[email protected]>; Ahmed Mansour >> <[email protected]>; [email protected] >> Cc: De Lara Guarch, Pablo <[email protected]>; Athreya, >> Narayana Prasad >> <[email protected]>; Gupta, Ashish >> <[email protected]>; Sahu, Sunila >> <[email protected]>; Challa, Mahipal <[email protected]>; Jain, >> Deepak K >> <[email protected]>; Hemant Agrawal <[email protected]>; Roy >> Pledge >> <[email protected]>; Youri Querry <[email protected]>; >> [email protected]; Daly, Lee >> <[email protected]>; Jozwiak, TomaszX <[email protected]> >> Subject: RE: [dpdk-dev] [PATCH] compressdev: implement API - mbuf alternative >> >> HI Fiona >> >> So I understand we're moving away from mbufs because of its size limitation >> (64k) and cacheline overhead >> and their more suitability to n/w applications. Given that, I understand >> benefit of having another structure >> to input data but then what is proposal for ipcomp like application where >> mbuf usage may be a better >> option? Should we keep support for both (mbuf and this structure) so that >> apps can use appropriate data >> structure depending on their requirement. >[Fiona] An application can use pass buffers from an mbuf or mbuf chain to >compressdev by filling in the >compressdev struct fields with the mbuf meta-data, using >rte_pktmbuf_data_len(), >rte_pktmbuf_mtod(), rte_pktmbuf_mtophys(), etc >For simplicity I'd prefer to offer only 1 rather than 2 data formats on the >API. >We see storage applications rather than IPComp as the main use-case for >compressdev, so would prefer >to optimise for that. >Do you think otherwise?
[Shally] Yea. We plan to use it for ipcomp and other such possible n/w apps. So, we envision mbuf support as necessary. So, I think we can add two APIs one which process on rte_comp_op and other on rte_mbufs to make it simpler. > >> >> Further comments, on github. >> >> Thanks >> Shally >> >> >-----Original Message----- >> >From: Trahe, Fiona [mailto:[email protected]] >> >Sent: 12 March 2018 21:31 >> >To: Ahmed Mansour <[email protected]>; Verma, Shally >> ><[email protected]>; >> [email protected] >> >Cc: De Lara Guarch, Pablo <[email protected]>; Athreya, >> >Narayana Prasad >> <[email protected]>; >> >Gupta, Ashish <[email protected]>; Sahu, Sunila >> ><[email protected]>; Challa, Mahipal >> ><[email protected]>; Jain, Deepak K <[email protected]>; >> >Hemant Agrawal >> <[email protected]>; Roy >> >Pledge <[email protected]>; Youri Querry <[email protected]>; >> >[email protected]; Daly, >> Lee <[email protected]>; >> >Jozwiak, TomaszX <[email protected]> >> >Subject: RE: [dpdk-dev] [PATCH] compressdev: implement API - mbuf >> >alternative >> > >> >Hi Shally, Ahmed, and anyone else interested in compressdev, >> > >> >I mentioned last week that we've been exploring using something other than >> >mbufs to pass src/dst >> buffers to compressdev PMDs. >> > >> >Reasons: >> > - mbuf data is limited to 64k-1 in each segment of a chained mbuf. Data >> > for compression >> > can be greater and it would add cycles to have to break up into smaller >> > segments. >> > - data may originate in mbufs, but is more likely, particularly for >> > storage use-cases, to >> > originate in other data structures. >> > - There's a 2 cache-line overhead for every segment in a chain, most of >> > this data >> > is network-related, not needed by compressdev >> >So moving to a custom structure would minimise memory overhead, remove >> >restriction on 64k-1 size and >> give more flexibility if >> >compressdev ever needs any comp-specific meta-data. >> > >> >We've come up with a compressdev-specific structure using the struct iovec >> >from sys/uio.h, which is >> commonly used by storage >> >applications. This would replace the src and dest mbufs in the op. >> >I'll not include the code here - Pablo will push that to github shortly and >> >we'd appreciate review >> comments there. >> >https://github.com/pablodelara/dpdk-draft-compressdev >> >Just posting on the mailing list to give a heads-up and ensure this reaches >> >a wider audience than may see >> it on github. >> > >> >Note : We also considered having no data structures in the op, instead the >> >application >> >would supply a callback which the PMD would use to retrieve meta-data (virt >> >address, iova, length) >> >for each next segment as needed. While this is quite flexible and allow the >> >application >> >to keep its data in its native structures, it's likely to cost more cycles. >> >So we're not proposing this at the moment, but hope to benchmark it later >> >while the API is still >> experimental. >> > >> >General feedback on direction is welcome here on the mailing list. >> >For feedback on the details of implementation we would appreciate comments >> >on github. >> > >> >Regards, >> >Fiona.
