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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 30A79C432BE for ; Fri, 27 Aug 2021 21:41:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1661660F35 for ; Fri, 27 Aug 2021 21:41:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231985AbhH0VmN (ORCPT ); Fri, 27 Aug 2021 17:42:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231696AbhH0VmM (ORCPT ); Fri, 27 Aug 2021 17:42:12 -0400 Received: from mail-io1-xd2a.google.com (mail-io1-xd2a.google.com [IPv6:2607:f8b0:4864:20::d2a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 31F77C0613D9; Fri, 27 Aug 2021 14:41:23 -0700 (PDT) Received: by mail-io1-xd2a.google.com with SMTP id a15so10474230iot.2; Fri, 27 Aug 2021 14:41:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=hZLiKEdmxy2XymDIV79zNDsfKqVBV5SHf0jshhrTnSg=; b=UY+h+XuCx+JsjRmG9x4MbhZKnih3FW6xx7c8U2nqe0reS52OXYNkd30F3rgFF2gc8h ++hzosS6lZ3I4aJgTlFWy5hgy+agZLOYYo3NR22f0e2XrsGpEeogYxFe0OVz/1k9QrKk kq4UHdbCpsSJ7qQgrP4blPM9Ix3BTTn2EleLpPkWcgB5/6io9O3fOAiVR+IVkYGJHOGW TDVEy8IqoGyw8+2OAD+MWpJtHPHpHIow7MuQsh3DsM5+FJr5Ue5iim0E0Y8Dn42aw5D7 Rk1GDVnH9IjUAsB2RJlWlZz/KODQn/fjI46vMkCwRqkAg5G4TMW2rfkR7R0Xw7D54SBz smQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=hZLiKEdmxy2XymDIV79zNDsfKqVBV5SHf0jshhrTnSg=; b=T3bK/DLYB3S14PSlY6WuGBLaNsmO2LeHGbX7jgHA3p74h1sObP1+qJiUI7iQXIcLdz EqfKeKWOfmrpsQZNYm4Uxva1fYOFBha7LaejDvYQ8mAbIv6BQbHy/tRgE9kPZf0/hIom dAV4tbBqNOTUk4Uck70u9H9oK63QO39R0rLaMzTZLwOcDAiIPpH+ECAYo3RLdM/GXDjq /7iv2FCgsMDv7SI38IiO7KZwtFgQuqVtQsjj/iMlAXihmXh/Kcj8svR5sN9kRujmpm9+ RZ5kdGVuSA94qasFRhTk4YWuG8ZcrBNdBFI93pK6yC31LspYq53Ur1c6PTBbi3LAKSQ2 JxUA== X-Gm-Message-State: AOAM530fDuSZ7ud+32bzATxxzURw4o/CALUG5TkkdZUNfhk5F/jmzYgk X9/IQz2QJHGxhd7eNso+RpQHyrAuTD6By/9sAoI= X-Google-Smtp-Source: ABdhPJyp4H1blX3LEu8j1s0mTA9EKMgRd2uYuAVN5JE6aTJmk/SpUOZAOkACDtaTD5IPGlE78hMZyI4/e2tq3PKbHQE= X-Received: by 2002:a6b:6319:: with SMTP id p25mr9282044iog.100.1630100482648; Fri, 27 Aug 2021 14:41:22 -0700 (PDT) MIME-Version: 1.0 References: <20210826004555.GF12597@magnolia> In-Reply-To: From: Dan Williams Date: Fri, 27 Aug 2021 14:41:11 -0700 Message-ID: Subject: Re: [GIT PULL] Memory folios for v5.15 To: Matthew Wilcox Cc: Johannes Weiner , "Darrick J. Wong" , Linus Torvalds , linux-mm , linux-fsdevel , Linux Kernel Mailing List , Andrew Morton Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Aug 27, 2021 at 11:47 AM Matthew Wilcox wrote: > > On Fri, Aug 27, 2021 at 10:07:16AM -0400, Johannes Weiner wrote: > > We have the same thoughts in MM and growing memory sizes. The DAX > > stuff said from the start it won't be built on linear struct page > > mappings anymore because we expect the memory modules to be too big to > > manage them with such fine-grained granularity. > > Well, I did. Then I left Intel, and Dan took over. Now we have a struct > page for each 4kB of PMEM. I'm not particularly happy about this change > of direction. Page-less DAX left more problems than it solved. Meanwhile, ZONE_DEVICE has spawned other useful things like peer-to-peer DMA. I am more encouraged by efforts to make the 'struct page' overhead disappear, first from Muchun Song for hugetlbfs and recently Joao Martins for device-dax. If anything, I think 'struct page' for PMEM / DAX *strengthens* the case for folios / better mechanisms to reduce the overhead of tracking 4K pages.