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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 E0284C433E0 for ; Wed, 27 Jan 2021 04:05:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB89F206B5 for ; Wed, 27 Jan 2021 04:05:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238049AbhA0EE7 (ORCPT ); Tue, 26 Jan 2021 23:04:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232151AbhA0DC5 (ORCPT ); Tue, 26 Jan 2021 22:02:57 -0500 Received: from mail-qt1-x82a.google.com (mail-qt1-x82a.google.com [IPv6:2607:f8b0:4864:20::82a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E5F76C0613D6 for ; Tue, 26 Jan 2021 18:10:24 -0800 (PST) Received: by mail-qt1-x82a.google.com with SMTP id d15so391480qtw.12 for ; Tue, 26 Jan 2021 18:10:24 -0800 (PST) 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; bh=4v1/VsnWd7cCCScK14wU43pHTF0mwW1R+KHNpMyduoM=; b=QtgkYDjdrXnX3O2BFxjAklfiousu1Sl+iOeoc4yAzZYkzrVEDYbJ0qQjZgocH+2YK2 BTpQU7A7m7npijAh4Oz3Jn6GrLOO/+s0tPyOjVsGyzUunp2NfSqFvkqb+J2Gg0+RMYfw 1l13jM6V4e+nYSHXkq4138OiRIfKGWpnAhsOE/kh2SA1wjp6V+C9gqvAsiB56JGyegZ8 TQv0+B9vZZuqzCBe9qjQ3baTKVjk/t63qRe9P7wDWWywMapEiOYkWmV7z0q12PeBN1X+ VaHM/ZMdw0aTMpjZw4UaYhbzqU6viC5SmBsvGp7m03sDjlcsCaoj0khA9SHgYuuZvIKI ucng== 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; bh=4v1/VsnWd7cCCScK14wU43pHTF0mwW1R+KHNpMyduoM=; b=OFu4Ek71o3W0smpBpGJkLhDKI6gPcR3L9N7HGKka+gGd8MVam8mkeQ0/eIDHoup0/y vvfo17gafW0LGXzhqfNgTlamHt3TGIhe7QcIq0n8q5Qm54qTA4Eyxxg8ie7fJfia+Myd 9/yzJwGWwW7D/lvfzGSarzICLzRwGx/Tsxv2vPqyJQ3+nPqoSbWqlGOwZktT4aTnSEMk lhHPUcjGBHEk5DNmJSeQSo1/QdC5s/dwRG35FWml+CU4LIrDSin4V2mtHtePQBP7U7qW eGt3uurTCbCMa15DINZjf7rUbEPkn4gakUglXpbwPWEN4fZrxutLgAiNSTCzEc/h9x7c pU3A== X-Gm-Message-State: AOAM5313bvDcoZIvF4lA9jVapHplJUMswjciC1qi9TqxLLbF8z0KgXeg PE5/7ieTHbC0MGr9Leoqrtnxjg== X-Google-Smtp-Source: ABdhPJwivhDVE44NS/6qidVgdRbB9DEIkPCwS6n93fVGJYIt5UiZwyEjF0M7IWPJK7sxbEzxD9X3nA== X-Received: by 2002:ac8:718f:: with SMTP id w15mr7950345qto.179.1611713424170; Tue, 26 Jan 2021 18:10:24 -0800 (PST) Received: from ziepe.ca (hlfxns017vw-142-162-115-133.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.115.133]) by smtp.gmail.com with ESMTPSA id p23sm455107qtu.4.2021.01.26.18.10.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Jan 2021 18:10:23 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1l4aHn-007JtW-3N; Tue, 26 Jan 2021 22:10:23 -0400 Date: Tue, 26 Jan 2021 22:10:23 -0400 From: Jason Gunthorpe To: Mike Kravetz Cc: "Matthew Wilcox (Oracle)" , Joao Martins , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , John Hubbard , Dave Hansen Subject: Re: [PATCH 2/2] mm/hugetlb: refactor subpage recording Message-ID: <20210127021023.GC4605@ziepe.ca> References: <20210125205744.10203-1-joao.m.martins@oracle.com> <20210125205744.10203-3-joao.m.martins@oracle.com> <3d34111f-8365-ab95-af11-aaf4825204be@oracle.com> <1ae0313d-de9b-4553-1f68-04c4f5a3f7eb@oracle.com> <4d3914e9-f448-8a86-9fc6-e71cec581115@oracle.com> <20210127000730.GB4605@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 26, 2021 at 05:58:53PM -0800, Mike Kravetz wrote: > As pointed out by Joao, you can also see the differences in pfn_to_page > for CONFIG_SPARSE_VMEMMAP and CONFIG_SPARSEMEM. The only time we might > have issues is with CONFIG_SPARSEMEM. I would bet CONFIG_SPARSE_VMEMMAP > is far more common. I think it is fine to have a different pfn_to_page, it should just be illegal to combine pages into a compound if their tail pages are not linear in the map. Matt's folio work might present an option to audit the whole mm for this pattern and provide some folio_next_tail_page() accessor that does the fast thing - but I question the value of such a project for a 2008 era PPC platform with 16GB pages (seriously?) that may be using VMEMMAP today anyhow?? Maybe others know of more modern use cases Jason