Hi Dave and Damjan, Thanks for the suggestions. I will take them up.
Thanks, Nitin On 02-Jun-2018, at 5:27 PM, Dave Barach <dbar...@cisco.com<mailto:dbar...@cisco.com>> wrote: You’re encouraged to review patches on gerrit.fd.io<http://gerrit.fd.io/>, and to show up at the biweekly project call where we discuss such things. See https://wiki.fd.io/view/VPP/Meeting. Philosophical dissertations are off-topic for vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>. Thanks... Dave From: vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io> <vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>> On Behalf Of Nitin Saxena Sent: Friday, June 1, 2018 9:12 PM To: Damjan Marion <dmar...@me.com<mailto:dmar...@me.com>> Cc: vpp-dev <vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>>; Athreya, Narayana Prasad <narayanaprasad.athr...@cavium.com<mailto:narayanaprasad.athr...@cavium.com>> Subject: Re: [vpp-dev] Multiarch/target select for dpdk_device_input Hi Damjan, If VPP is an open-source project that supports multiple architectures, then there should be a review of every commit which provides others using the open source project an opportunity to raise their concerns. So my request is to post changes for review before they are committed to ensure VPP stays true to open-source philosophy. Please let me know if this is possible. If not, i'd like to understand the reasons for it. Regards, Nitin On 02-Jun-2018, at 00:17, Damjan Marion <dmar...@me.com<mailto:dmar...@me.com>> wrote: Dear Nitin, That doesn't work that way. Regards, Damjan On 1 Jun 2018, at 19:41, Saxena, Nitin <nitin.sax...@cavium.com<mailto:nitin.sax...@cavium.com>> wrote: Hi Damjan, Now that you are aware that Cavium is working on optimisations for ARM, can I request that you check with us on implications for ARM(at least Cavium), before bringing changes in dpdk-input? Regards, Nitin On 01-Jun-2018, at 21:39, Damjan Marion <dmar...@me.com<mailto:dmar...@me.com>> wrote: Dear Nitin, I really don't have anything else to add. It your call how do you want to proceed.... Regards, Damjan On 1 Jun 2018, at 18:02, Nitin Saxena <nitin.sax...@cavium.com<mailto:nitin.sax...@cavium.com>> wrote: Hi Damjan, Answers Inline. Thanks, Nitin On Friday 01 June 2018 08:49 PM, Damjan Marion wrote: Hi Nitin, inline... On 1 Jun 2018, at 15:23, Nitin Saxena <nitin.sax...@cavium.com<mailto:nitin.sax...@cavium.com>> wrote: Hi Damjan, It was hard to know that you have subset of patches hidden somewhere. I wouldn't say patches are hidden. We are trying to fine tune dpdk-input initially from our end first and later we will seek your expertise while upstreaming. for me they were hidden. Typically it makes sense to discuss such kind of changes with person >who "maintains" the code before starting writing the code. Agreed. However we prefer to do internal analysis/POC first before reaching out to MAINTAINERS. That way we can better understand code review comments. Perfectly fine, but then don't put blame on us for not knowing that you are doing something internally... The intention was not to blame anybody but to understand modular approach in vpp to accommodate multi-arch(s). Maybe, but sounds to me like we are still in guessing phase. I wouldn't do any guess work with MAINTAINERS. Maybe we even need different function for each ARM CPU core as they maybe have different memory subsystem and pipeline.... This is what I am looking for. Is it ok to detect our hardware natively from autoconf and append target specific macro to CFLAGS? And then separate function for our target in dpdk/device/node.c? Sorry my multi-arch select example was incorrect and that's not what I am looking at. Here I will be able to help when I get reasonable understanding what is the "big" plan. The "Big" plan is to optimize each vpp node for Aarch64. For now focus is dpdk-input. I don't want that we end up in 6 months with cavium patches, nxp patches, marvell patches, and so on. Is it a problem? If yes than I am not able to visualize it as the same problem would exist for any architecture and not just for Aarch64. Is there an agreement between ARM vendors what is the targeted core you want to have code tuned for or you are simply tuning to whatever core Cavium uses? I am trying to optimize Cavium's SOC. This question is in this regard only. However efforts are going on optimizing Cortex cores as well by ARM community. What about agreeing on plan for optimising on all ARM cores, and then starting doing optimisation? This is cross-company question so hard to answer but Cavium has the "big" plan described above. Thanks, Nitin On Friday 01 June 2018 01:55 AM, Damjan Marion wrote: inline... -- Damjan On 31 May 2018, at 21:10, Saxena, Nitin <nitin.sax...@cavium.com<mailto:nitin.sax...@cavium.com><mailto:nitin.sax...@cavium.com>> wrote: Hi Damjan, Answers inline. Thanks, Nitin On 01-Jun-2018, at 12:15 AM, Damjan Marion <dmarion.li...@gmail.com<mailto:dmarion.li...@gmail.com><mailto:dmarion.li...@gmail.com>> wrote: Dear Nitin, See inline…. On 31 May 2018, at 19:59, Nitin Saxena <nitin.sax...@cavium.com<mailto:nitin.sax...@cavium.com><mailto:nitin.sax...@cavium.com>> wrote: Hi, I am working on optimising dpdk-input node (based on vpp v1804) for our target. I am able to get performance improvements on our target but the problem I am finding now are: 1) The dpdk-input code is completely changed on master branch from v1804. Why is this a problem? It was done with reason and for tangible benefit. This is a problem for me as I can not apply my v1804 changes directly to the master branch. I have to again rework on master branch and that’s why I am not able to move to master branch or v1807 in future. It was hard to know that you have subset of patches hidden somewhere. Typically it makes sense to discuss such kind of changes with person who "maintains" the code before starting writing the code. Not to mention the dpdk-input master branch code do not give better numbers on our target as compared to v1804 Sad to hear that, good thing is, it gives better numbers on x86. As I understand one dpdk_device_input function cannot be same for all architectures because if the underlying micro-architecture is different, the hot spots changes. Maybe, but sounds to me like we are still in guessing phase. Maybe we even need different function for each ARM CPU core as they maybe have different memory subsystem and pipeline.... Is there an agreement between ARM vendors what is the targeted core you want to have code tuned for or you are simply tuning to whatever core Cavium uses? I have seen dpdk-input master branch changes and on a positive notes those changes make sense however some codes are tuned for x86 specially Skylake. I was looking for some kind of way to have mutiarch select function for the Rx path, like the way it’s done for tx path. Not sure why do you need that, unless you are going to have code optimised for different CPU variants (i.e. Cortex-A53 and Cortex-A72) in the same binary. 2) I don’t know the modular approach I should follow to merge my changes as I have completely changed the quad loop handling and the prefetches order in dpdk-input. I carefully tuned that code. It was multi day exercise and losing single clock/packet on x86 with additional modifications are not acceptable. Still I’m open for discussion how to address this problem. Note: I am far away from upstreaming the code currently as my optimisation is still in progress. It will be better if I know the proper way of doing it. I suggest that you don’t even start on working on upstreaming before we have deep understanding of what and why needs to be done and we are all in agreement. Thanks, Nitin
