From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Burakov, Anatoly" Subject: Re: [PATCH 3/5] common/dpaax: add library for PA VA translation table Date: Tue, 25 Sep 2018 14:51:31 +0100 Message-ID: <67e25f1a-110c-db32-5f3b-a065e77fecc6@intel.com> References: <20180925125423.7505-1-shreyansh.jain@nxp.com> <20180925125423.7505-4-shreyansh.jain@nxp.com> <894130a9-017c-348d-31f8-c4c23f517f25@nxp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: ferruh.yigit@intel.com, dev@dpdk.org To: Shreyansh Jain Return-path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id 490CE1B185 for ; Tue, 25 Sep 2018 15:51:51 +0200 (CEST) In-Reply-To: <894130a9-017c-348d-31f8-c4c23f517f25@nxp.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 25-Sep-18 2:39 PM, Shreyansh Jain wrote: > Hello Anatoly, > > On Tuesday 25 September 2018 06:58 PM, Burakov, Anatoly wrote: >> On 25-Sep-18 1:54 PM, Shreyansh Jain wrote: >>> A common library, valid for dpaaX drivers, which is used to maintain >>> a local copy of PA->VA translations. >>> >>> In case of physical addressing mode (one of the option for FSLMC, and >>> only option for DPAA bus), the addresses of descriptors Rx'd are >>> physical. These need to be converted into equivalent VA for rte_mbuf >>> and other similar calls. >>> >>> Using the rte_mem_virt2iova or rte_mem_virt2phy is expensive. This >>> library is an attempt to reduce the overall cost associated with >>> this translation. >>> >>> A small table is maintained, containing continuous entries >>> representing a continguous physical range. Each of these entries >>> stores the equivalent VA, which is fed during mempool creation, or >>> memory allocation/deallocation callbacks. >>> >>> Signed-off-by: Shreyansh Jain >>> --- >> >> Hi Shreyansh, >> >> So, basically, you're reimplementing old DPDK's memory view (storing >> VA's in a PA-centric way). Makes sense :) > > Yes, and frankly, I couldn't come up with any other way. > >> >> I should caution you that right now, external memory allocator >> implementation does *not* trigger any callbacks for newly added >> memory. So, anything coming from external memory will not be reflected >> in your table, unless it happens to be already there before >> dpaax_iova_table_populate() gets called. This patchset makes a good >> argument for why perhaps it should trigger callbacks. Thoughts? > > Oh. Then I must be finishing reading through your patches for external > memory sooner. I didn't realize this. To be clear, the current implementation of external memory allocators is not necessarily final - it's not too late to add callbacks to enable your use case better, if that's required (and it should be pretty easy to implement as well). -- Thanks, Anatoly