> -----Original Message----- > From: dev <dev-boun...@dpdk.org> On Behalf Of Ferruh Yigit > Sent: Tuesday, October 15, 2019 10:17 PM > To: Vamsi Krishna Attunuru <vattun...@marvell.com>; dev@dpdk.org > Cc: arybche...@solarflare.com; Jerin Jacob Kollanukkaran > <jer...@marvell.com>; tho...@monjalon.net > Subject: Re: [dpdk-dev] [PATCH v2 1/3] lib/ethdev: add ethdev op to get hash > index > > On 10/15/2019 10:52 AM, vattun...@marvell.com wrote: > > From: Vamsi Attunuru <vattun...@marvell.com> > > > > Some networking devices may use custom algos for computing hash > > indices and spread the packets accordingly. > > > > Patch adds an eth_dev op to get the hash index correspond to the given > > hash value received in the initial packet on the given port. > > > > Some of the applications compute hash index from the hash value > > received in the initial packet and than configure the rxq to lcore > > mapping to make sure the mapped lcore/rxq would receive the upcoming > > traffic that has similar hash. > > Such applications may use these API to get the hash index used by the > > PMD for spreading those traffic. > > Hi Vamsi, > > Can you please describe this usecase? > If the application is receiving the packet, it already knows which queue it is > coming from, what is the benefit of the getting hash index?
Hi Ferruh, I think the commit msg is incomplete and did not explain the use case clearly, my apologies. Actual usecase is when application precalculates the hash value using some hashlib for a specific type of packet headers with the same hash key that's configured in the HW, application would compute hash_index as hash % reta_size and predict the packets on the computed queue index. But these hash_index computation might be different from PMD/HW computed index(based it's algo design). To fix those disparity, these API been introduced which can be used during configuration time to have required lcore-rq mapping. > > The concern is adding a new API which is specific to a use case and HW and > won't be used in long term. That will only create technical dept for us. > > > > > Signed-off-by: Vamsi Attunuru <vattun...@marvell.com> > > <...>
