From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C86DAC43381 for ; Fri, 29 Mar 2019 01:59:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 971B22173C for ; Fri, 29 Mar 2019 01:59:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728487AbfC2B70 (ORCPT ); Thu, 28 Mar 2019 21:59:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34514 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727434AbfC2B70 (ORCPT ); Thu, 28 Mar 2019 21:59:26 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4A6BA3086205; Fri, 29 Mar 2019 01:59:25 +0000 (UTC) Received: from redhat.com (ovpn-121-118.rdu2.redhat.com [10.10.121.118]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DC41C8958A; Fri, 29 Mar 2019 01:59:23 +0000 (UTC) Date: Thu, 28 Mar 2019 21:59:19 -0400 From: Jerome Glisse To: John Hubbard Cc: Ira Weiny , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Dan Williams Subject: Re: [PATCH v2 07/11] mm/hmm: add default fault flags to avoid the need to pre-fill pfns arrays. Message-ID: <20190329015919.GF16680@redhat.com> References: <20190328221203.GF13560@redhat.com> <555ad864-d1f9-f513-9666-0d3d05dbb85d@nvidia.com> <20190328223153.GG13560@redhat.com> <768f56f5-8019-06df-2c5a-b4187deaac59@nvidia.com> <20190328232125.GJ13560@redhat.com> <20190328164231.GF31324@iweiny-DESK2.sc.intel.com> <20190329011727.GC16680@redhat.com> <20190329014259.GD16680@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190329014259.GD16680@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Fri, 29 Mar 2019 01:59:25 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 28, 2019 at 09:42:59PM -0400, Jerome Glisse wrote: > On Thu, Mar 28, 2019 at 06:30:26PM -0700, John Hubbard wrote: > > On 3/28/19 6:17 PM, Jerome Glisse wrote: > > > On Thu, Mar 28, 2019 at 09:42:31AM -0700, Ira Weiny wrote: > > >> On Thu, Mar 28, 2019 at 04:28:47PM -0700, John Hubbard wrote: > > >>> On 3/28/19 4:21 PM, Jerome Glisse wrote: > > >>>> On Thu, Mar 28, 2019 at 03:40:42PM -0700, John Hubbard wrote: > > >>>>> On 3/28/19 3:31 PM, Jerome Glisse wrote: > > >>>>>> On Thu, Mar 28, 2019 at 03:19:06PM -0700, John Hubbard wrote: > > >>>>>>> On 3/28/19 3:12 PM, Jerome Glisse wrote: > > >>>>>>>> On Thu, Mar 28, 2019 at 02:59:50PM -0700, John Hubbard wrote: > > >>>>>>>>> On 3/25/19 7:40 AM, jglisse@redhat.com wrote: > > >>>>>>>>>> From: Jérôme Glisse > > >>> [...] > > >> Indeed I did not realize there is an hmm "pfn" until I saw this function: > > >> > > >> /* > > >> * hmm_pfn_from_pfn() - create a valid HMM pfn value from pfn > > >> * @range: range use to encode HMM pfn value > > >> * @pfn: pfn value for which to create the HMM pfn > > >> * Returns: valid HMM pfn for the pfn > > >> */ > > >> static inline uint64_t hmm_pfn_from_pfn(const struct hmm_range *range, > > >> unsigned long pfn) > > >> > > >> So should this patch contain some sort of helper like this... maybe? > > >> > > >> I'm assuming the "hmm_pfn" being returned above is the device pfn being > > >> discussed here? > > >> > > >> I'm also thinking calling it pfn is confusing. I'm not advocating a new type > > >> but calling the "device pfn's" "hmm_pfn" or "device_pfn" seems like it would > > >> have shortened the discussion here. > > >> > > > > > > That helper is also use today by nouveau so changing that name is not that > > > easy it does require the multi-release dance. So i am not sure how much > > > value there is in a name change. > > > > > > > Once the dust settles, I would expect that a name change for this could go > > via Andrew's tree, right? It seems incredible to claim that we've built something > > that effectively does not allow any minor changes! > > > > I do think it's worth some *minor* trouble to improve the name, assuming that we > > can do it in a simple patch, rather than some huge maintainer-level effort. > > Change to nouveau have to go through nouveau tree so changing name means: > - release N add function with new name, maybe make the old function just > a wrapper to the new function > - release N+1 update user to use the new name > - release N+2 remove the old name > > So it is do-able but it is painful so i rather do that one latter that now > as i am sure people will then complain again about some little thing and it > will post pone this whole patchset on that new bit. To avoid post-poning > RDMA and bunch of other patchset that build on top of that i rather get > this patchset in and then do more changes in the next cycle. > > This is just a capacity thing. Also for clarity changes to API i am doing in this patchset is to make the ODP convertion easier and thus they bring a real hard value. Renaming those function is esthetic, i am not saying it is useless, i am saying it does not have the same value as those other changes and i would rather not miss another merge window just for esthetic changes. Cheers, Jérôme