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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 97963C433E0 for ; Fri, 29 May 2020 23:24:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 56E092068D for ; Fri, 29 May 2020 23:24:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="IKwS+7d7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 56E092068D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B6C3F80010; Fri, 29 May 2020 19:24:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B1C5280008; Fri, 29 May 2020 19:24:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9E41080010; Fri, 29 May 2020 19:24:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0217.hostedemail.com [216.40.44.217]) by kanga.kvack.org (Postfix) with ESMTP id 8560780008 for ; Fri, 29 May 2020 19:24:52 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 3F04B3D12 for ; Fri, 29 May 2020 23:24:52 +0000 (UTC) X-FDA: 76871338824.01.tank84_64ae07833dd43 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id 1C9BC1803A54F for ; Fri, 29 May 2020 23:24:52 +0000 (UTC) X-HE-Tag: tank84_64ae07833dd43 X-Filterd-Recvd-Size: 6021 Received: from mail-qk1-f196.google.com (mail-qk1-f196.google.com [209.85.222.196]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Fri, 29 May 2020 23:24:51 +0000 (UTC) Received: by mail-qk1-f196.google.com with SMTP id 205so3883612qkg.3 for ; Fri, 29 May 2020 16:24:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=NGBn/AuzNZpYdh5SlPF2DkI93ztTCm2iyZ9aPkUohiY=; b=IKwS+7d7WuYKZu+Q4GbtHw2D0LkjSL5A7lbo392iOd2v43Z52P0dFEEYFCiMEnQ/56 qHXRFTF3iYnEeR12Gy6AN1N5Ko5uNF6SGa8LgjOUNf8ofjtnodQ2Wa/NwtsqJSS9TAys Gg2F/FQkn7AKIU6PXRK/IbsFEIAuxiMa6Q3VFGdqW0PKTMO71Ulqc96eqRatHrZT+job CmB7I7tKfzmPXdiHFwtNNVdIZthAMoYLj8buxmbD42FxW/NSzvPxiyagJjl2OyvsdhpD S5MOG5N3YQf1bbr8iJo0die/KuV0BMoW3Ysy/3VNSMrpD8wNAee0a8qz06MN/4Fpt6fO lZZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=NGBn/AuzNZpYdh5SlPF2DkI93ztTCm2iyZ9aPkUohiY=; b=h/R3xy6lVfAnhQSYhJnRJvtZZhzAmrU0rcbkoloQCLTO23ZZsdEZ7AG0pe7FiMqgXJ hZtWlIFaAajc2t8LIsEguPfmzUEIqkmpwMDxoKFcRbBvDrbun4N3v3qApiZtv2PUhhV7 bQlYA2w00odBlNL9n4wLbut1+st4cwTY7bzxAm8ZrSmhw5xQBGz8ISX2DV+LTiZMthDP MLVhmD32yF0qabR6bfL+7VZfp2LeV9B1csztM/ntrpNBEZimq9QSKWa+ILJ3COqLwVpG MYqv95oeOv7CkExFSJkSRqyI/TNjulnOazjv+iO0IOOnAm7IrYVpJvzn84n6ZbEflM9U rV6w== X-Gm-Message-State: AOAM532TfYJahE33YrfKL/e3E/E+soGeWwAJMmpMevDirHO+8FBTHv6G rndimAwI3eoj8KYf7RbswP150g== X-Google-Smtp-Source: ABdhPJzKrllspgHFufnfAlSPKJ28Ce9a8Ik5xQzMRPQlXECpMQP4AXzw/tDE7D+9+tIgrQIxQDZLBQ== X-Received: by 2002:a05:620a:102c:: with SMTP id a12mr10189193qkk.214.1590794691029; Fri, 29 May 2020 16:24:51 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-156-34-48-30.dhcp-dynamic.fibreop.ns.bellaliant.net. [156.34.48.30]) by smtp.gmail.com with ESMTPSA id h19sm3668912qkl.49.2020.05.29.16.24.50 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 29 May 2020 16:24:50 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jeoMr-0000gH-PQ; Fri, 29 May 2020 20:24:49 -0300 Date: Fri, 29 May 2020 20:24:49 -0300 From: Jason Gunthorpe To: Ralph Campbell Cc: nouveau@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Jerome Glisse , John Hubbard , Christoph Hellwig , Ben Skeggs , Andrew Morton , Shuah Khan Subject: Re: [PATCH 0/6] nouveau/hmm: add support for mapping large pages Message-ID: <20200529232449.GC21651@ziepe.ca> References: <20200508192009.15302-1-rcampbell@nvidia.com> <20200525134118.GA2536@ziepe.ca> <4743ec6e-a5a0-16ac-a1b8-992f851515f0@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4743ec6e-a5a0-16ac-a1b8-992f851515f0@nvidia.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Rspamd-Queue-Id: 1C9BC1803A54F X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 26, 2020 at 10:32:48AM -0700, Ralph Campbell wrote: > > On 5/25/20 6:41 AM, Jason Gunthorpe wrote: > > On Fri, May 08, 2020 at 12:20:03PM -0700, Ralph Campbell wrote: > > > hmm_range_fault() returns an array of page frame numbers and flags for > > > how the pages are mapped in the requested process' page tables. The PFN > > > can be used to get the struct page with hmm_pfn_to_page() and the page size > > > order can be determined with compound_order(page) but if the page is larger > > > than order 0 (PAGE_SIZE), there is no indication that the page is mapped > > > using a larger page size. To be fully general, hmm_range_fault() would need > > > to return the mapping size to handle cases like a 1GB compound page being > > > mapped with 2MB PMD entries. However, the most common case is the mapping > > > size the same as the underlying compound page size. > > > This series adds a new output flag to indicate this so that callers know it > > > is safe to use a large device page table mapping if one is available. > > > Nouveau and the HMM tests are updated to use the new flag. > > > > > > Note that this series depends on a patch queued in Ben Skeggs' nouveau > > > tree ("nouveau/hmm: map pages after migration") and the patches queued > > > in Jason's HMM tree. > > > There is also a patch outstanding ("nouveau/hmm: fix nouveau_dmem_chunk > > > allocations") that is independent of the above and could be applied > > > before or after. > > > > Did Christoph and Matt's remarks get addressed here? > > Both questioned the need to add the HMM_PFN_COMPOUND flag to the > hmm_range_fault() output array saying that the PFN can be used to get the > struct page pointer and the page can be examined to determine the page size. > My response is that while is true, it is also important that the device only > access the same parts of a large page that the process/cpu has access to. > There are places where a large page is mapped with smaller page table entries > when a page is shared by multiple processes. > After I explained this, I haven't seen any further comments from Christoph > and Matt. I'm still looking for reviews, acks, or suggested changes. Okay, well, we reached the merge window, so since there may be some conflicts repost again in three weeks. It would be more compelling if there was some performance data if it is much of a win vs the 'compute large page' algorithm something like ODP uses. Jason