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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 8E96AC433EF for ; Wed, 22 Sep 2021 15:46:12 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2BF7561181 for ; Wed, 22 Sep 2021 15:46:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2BF7561181 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 71EAB940008; Wed, 22 Sep 2021 11:46:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6CE936B007D; Wed, 22 Sep 2021 11:46:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 56F54940008; Wed, 22 Sep 2021 11:46:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0235.hostedemail.com [216.40.44.235]) by kanga.kvack.org (Postfix) with ESMTP id 48AB16B007B for ; Wed, 22 Sep 2021 11:46:11 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0239128499 for ; Wed, 22 Sep 2021 15:46:11 +0000 (UTC) X-FDA: 78615635742.19.A39006B Received: from mail-qt1-f171.google.com (mail-qt1-f171.google.com [209.85.160.171]) by imf20.hostedemail.com (Postfix) with ESMTP id AC869D0000B1 for ; Wed, 22 Sep 2021 15:46:10 +0000 (UTC) Received: by mail-qt1-f171.google.com with SMTP id r1so3040818qta.12 for ; Wed, 22 Sep 2021 08:46:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=wVGktONlyuLsWAH2exvLKeS5CnFnKlgLM/sI96OfsNs=; b=RsvJWdyEk4lgnjYlT+5aTgeWpdCg9TY9iCo4rvHUm3ntJ8Yxss8iPsFarkKFVBWQXP kzDE/SSKgkRL9uvrxYdZERgjUWlIFZuUAlX/xuuR9+fYNVfo1cSpAT+3QCwx/UdAO9sD mnJRJ2KMDRbiDhzpKCajxToxgkICsGf6UNdrmuif94uwD2f2zFu11TojoW9+R5wG0ZR1 xeT+ZpweVDQyYMNeJZzqf3xyE8qDkpaw7Mth6VyPxo0O96lQ0GC+kaPbmlZECWHtfBvl ZupaI/Pa56VXmGl+p61hLnk6bpbPr5mZMGdAu9+13IwdlY/pJzAf0lnln6MgQEHV2Zuw kJkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=wVGktONlyuLsWAH2exvLKeS5CnFnKlgLM/sI96OfsNs=; b=vkJn8MVLQVndKApOnMNEDc/8qNjerTzs3juzo+jQ27vcHNxadY6U1MNmYpoHMQbHxn pCXWY65Oc6ifbO8uSDyzLhLyjP7Z+VGQK/IeMXNJbqz/88Sufx8TBIfg9IRe1qbNbX4m f6AsgDAzkONr9YH+6qKm0zhzlqny4txTMIML1LZHOqEYDe8eHAuuwne7p5ecfAkFaVP8 OuW6xY0nvnycXazz57ox/1tTmqNIBjVCfNtvxt83ked9PzDNTkUP1PF2bm7E7ASn3Yfq qC10W+ZS/5KwJtJsRfAM+bRiyuIKVVYt9a9RME+J8MFytn2M6MPl0YTKGQ5mesbOoO27 zNGw== X-Gm-Message-State: AOAM533uJvHVWnX8VrCyECPYIc9zHJggvUX2JgdfzvUqOFRVKy9RMQSj J+NdGAJbG3OODmCuxOll1A== X-Google-Smtp-Source: ABdhPJztTNAUbBMNBlNnPXcMDhxgBdw9YffnsLygCsPZLbtbKSwLXYYq+eWEbgddnxnskOXGS63pPg== X-Received: by 2002:ac8:6683:: with SMTP id d3mr141145qtp.291.1632325570011; Wed, 22 Sep 2021 08:46:10 -0700 (PDT) Received: from moria.home.lan (c-73-219-103-14.hsd1.vt.comcast.net. [73.219.103.14]) by smtp.gmail.com with ESMTPSA id a3sm552437qkh.67.2021.09.22.08.46.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Sep 2021 08:46:09 -0700 (PDT) Date: Wed, 22 Sep 2021 11:46:04 -0400 From: Kent Overstreet To: Johannes Weiner Cc: Linus Torvalds , Matthew Wilcox , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , "Darrick J. Wong" , Christoph Hellwig , David Howells Subject: Re: Folios for 5.15 request - Was: re: Folio discussion recap - Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=RsvJWdyE; spf=pass (imf20.hostedemail.com: domain of kent.overstreet@gmail.com designates 209.85.160.171 as permitted sender) smtp.mailfrom=kent.overstreet@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: o1i8mus318jf94y4gfaszoxmbch43nsf X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: AC869D0000B1 X-HE-Tag: 1632325570-431291 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 Wed, Sep 22, 2021 at 11:08:58AM -0400, Johannes Weiner wrote: > On Tue, Sep 21, 2021 at 05:22:54PM -0400, Kent Overstreet wrote: > > - it's become apparent that there haven't been any real objections to the code > > that was queued up for 5.15. There _are_ very real discussions and points of > > contention still to be decided and resolved for the work beyond file backed > > pages, but those discussions were what derailed the more modest, and more > > badly needed, work that affects everyone in filesystem land > > Unfortunately, I think this is a result of me wanting to discuss a way > forward rather than a way back. > > To clarify: I do very much object to the code as currently queued up, > and not just to a vague future direction. > > The patches add and convert a lot of complicated code to provision for > a future we do not agree on. The indirections it adds, and the hybrid > state it leaves the tree in, make it directly more difficult to work > with and understand the MM code base. Stuff that isn't needed for > exposing folios to the filesystems. > > As Willy has repeatedly expressed a take-it-or-leave-it attitude in > response to my feedback, I'm not excited about merging this now and > potentially leaving quite a bit of cleanup work to others if the > downstream discussion don't go to his liking. > > Here is the roughly annotated pull request: Thanks for breaking this out, Johannes. So: mm/filemap.c and mm/page-writeback.c - I disagree about folios not really being needed there. Those files really belong more in fs/ than mm/, and the code in those files needs folios the most - especially filemap.c, a lot of those algorithms have to change from block based to extent based, making the analogy with filesystems. I think it makes sense to drop the mm/lru stuff, as well as the mm/memcg, mm/migrate and mm/workingset and mm/swap stuff that you object to - that is, the code paths that are for both file + anonymous pages, unless Matthew has technical reasons why that would break the rest of the patch set. And then, we really should have a pow wow and figure out what our options are going forward. I think we have some agreement now that not everything is going to be a folio going forwards (Matthew already split out his slab conversion to a new type) - so if anonymous pages aren't becoming folios, we should prototype some stuff and see where that helps and hurts us. > As per the other email I still think it would have been good to have a > high-level discussion about the *legitimate* entry points and data > structures that will continue to deal with tail pages down the > line. To scope the actual problem that is being addressed by this > inverted/whitelist approach - so we don't annotate the entire world > just to box in a handful of page table walkers... That discussion can still happen... and there's still the potential to get a lot more done if we're breaking open struct page and coming up with new types. I got Matthew on board with what you wanted, re: using the slab allocator for larger allocations