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 D1F20C433F5 for ; Wed, 22 Sep 2021 16:29:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1CA2611B0 for ; Wed, 22 Sep 2021 16:29:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236621AbhIVQaz (ORCPT ); Wed, 22 Sep 2021 12:30:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57326 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229671AbhIVQax (ORCPT ); Wed, 22 Sep 2021 12:30:53 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF66BC061574; Wed, 22 Sep 2021 09:29:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=/bg8mgxozFDsyBXWUCU4D/OveolCgwjbJqJNs7JQP/U=; b=fq8uuURZmuYEV+T6V8jh+sIKRT ZPzQVWXPFcxfKLNNntZnKahM60EK4OJCJX7/OIPx+S7y6wlL+0b4O9wI+JW6X3Jr513UYtFrsn+Fy R3VTvKuiy5tgk+kxvsN//YdoIv7wNdbl2PA+kny53pQWUVcgy7tNqtbWGgS6/PpZug+SsenI476B2 Dua80cSWa5zukDcLCwIe7rWL+KCSoDtZUSR7RtrWwkEVx8XWSDjo4r3hg6Tdx4J+ssS6uiKH+++JT j79U87wYVCuKdYEVrNNE00xcHl2s1cz7cGFkmnc4fCx+B51ahjr5qElcjLn0CJ1jhfkSSM+Lw00VP jOC5Y8kw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mT54h-004wPq-HM; Wed, 22 Sep 2021 16:26:52 +0000 Date: Wed, 22 Sep 2021 17:26:23 +0100 From: Matthew Wilcox To: Kent Overstreet Cc: Johannes Weiner , Linus Torvalds , 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: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 22, 2021 at 11:46:04AM -0400, Kent Overstreet wrote: > 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. We're at a take-it-or-leave-it point for this pull request. The time for discussion was *MONTHS* ago. > > 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. Conceptually, it breaks the patch set. Anywhere that we convert back from a folio to a page, the guarantee of folios is weakened (and possibly violated). I don't think it makes sense from a practical point of view either; it's re-adding compound_head() calls that just don't need to be there. > 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 Wait, no, you didn't. I think it's a terrible idea. It's just completely orthogonal to this patch set, so I don't want to talk about it.