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 BF238C433E6 for ; Thu, 14 Jan 2021 13:06:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9791F23A5C for ; Thu, 14 Jan 2021 13:06:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726147AbhANNG0 (ORCPT ); Thu, 14 Jan 2021 08:06:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727610AbhANNGZ (ORCPT ); Thu, 14 Jan 2021 08:06:25 -0500 Received: from mail-pg1-x532.google.com (mail-pg1-x532.google.com [IPv6:2607:f8b0:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A2DE2C061757 for ; Thu, 14 Jan 2021 05:05:45 -0800 (PST) Received: by mail-pg1-x532.google.com with SMTP id z21so3758499pgj.4 for ; Thu, 14 Jan 2021 05:05:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=otxZaMxXrqXQ+HB6nBjrd36W75JtcSkls6JE059kKq8=; b=Y5wdk5Z+2zXharmJBzMfvHlw+DCQOtiGesEKv/ljgEMRr2bZnbpYpeN5Rc6nkzBSU7 6GZaLZNf2+smELPyQ7e1VoARGBuINS5W3oUPrtBX3hmlAxujkz6OCS92eRfWqs8YR7cy SyIyelX801SjXYu3JKgZT72YIOJP8SANg6sSD8lt7xGj+VRtWODdLPAmAaofjvpLHQgi k7Fw7ZRWx8UOFc+lFuD4W6OhkoVyRMiwgORb5OSsnkjwmHOCfQpmzYUHG2WdxIqVeZ1k p5KFqGx34Rk9jsS+lk6PDzPCsRug5oPCXF5v/nfS/Bwd2xy8CiIrNOhyZcYR0HC6uE9e /y6w== 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=otxZaMxXrqXQ+HB6nBjrd36W75JtcSkls6JE059kKq8=; b=hlOIMgm3AeLXUEF8gd2ZddsO7SzEPCS9k/L8t99NMHmfrjxdqePiS7YUYyTK6VasTj QE0OVsIeomjmYQGhkODzwSmvpPCg25SPlVyameedy6clNqTetZIGGNpnkZpKtHnlSzSg OBC7FUsPS26vFmjqlK49BRUJen04BB7wPBfMc1fx8s04DUROt68TRupml+NofyPsuKu4 xazONTIZgH6D4QsnYX+MKOj59x3a2MglN4vayzpbS68cUoiszsPryX8uuC9hfE3Ky1TL OdAUmma7NsMNuNAhtpLFZiScqQedZSos+GkLrDxMAbS/atePXdIz/j7yD7tfd6LMbwR+ oXXQ== X-Gm-Message-State: AOAM530NoBgS5sUPsI5/K9ywGLH4OO/nCufZ2+tiqHYHjLStCi0sqzLg BdlLWkLfJP6/FdLlzf8vI0tV/hrsspPxx60KqbBOBg== X-Google-Smtp-Source: ABdhPJzXR6KWx5reUzFIFz1GMOxEjEoANCQaSp+5a9EX5pYZyQ4qs0zpJRJh7vxaZ4eM6E2Q8vb99n3CxNo6z+THTLU= X-Received: by 2002:a63:480f:: with SMTP id v15mr7419423pga.341.1610629545074; Thu, 14 Jan 2021 05:05:45 -0800 (PST) MIME-Version: 1.0 References: <20210106141931.73931-1-songmuchun@bytedance.com> <20210106141931.73931-5-songmuchun@bytedance.com> <20210112080453.GA10895@linux> <20210113092028.GB24816@linux> <20210114115248.GA24592@localhost.localdomain> In-Reply-To: <20210114115248.GA24592@localhost.localdomain> From: Muchun Song Date: Thu, 14 Jan 2021 21:05:06 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v12 04/13] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page To: Oscar Salvador Cc: Mike Kravetz , Jonathan Corbet , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Michal Hocko , "Song Bao Hua (Barry Song)" , David Hildenbrand , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Jan 14, 2021 at 7:52 PM Oscar Salvador wrote: > > On Thu, Jan 14, 2021 at 06:54:30PM +0800, Muchun Song wrote: > > I think this approach may be only suitable for generic huge page only. > > So we can implement it only for huge page. > > > > Hi Oscar, > > > > What's your opinion about this? > > I tried something like: > > static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr, > unsigned long end, > struct vmemmap_remap_walk *walk) > { > pte_t *pte; > > pte = pte_offset_kernel(pmd, addr); > > if (!walk->reuse_page) { > BUG_ON(pte_none(*pte)); > > walk->reuse_page = pte_page(*pte++); > addr = walk->remap_start; > } > > for (; addr != end; addr += PAGE_SIZE, pte++) { > BUG_ON(pte_none(*pte)); > > walk->remap_pte(pte, addr, walk); > } > } > > void vmemmap_remap_free(unsigned long start, unsigned long end, > unsigned long reuse) > { > LIST_HEAD(vmemmap_pages); > struct vmemmap_remap_walk walk = { > .remap_pte = vmemmap_remap_pte, > .reuse_addr = reuse, > .remap_start = start, > .vmemmap_pages = &vmemmap_pages, > }; > > BUG_ON(start != reuse + PAGE_SIZE); > > vmemmap_remap_range(reuse, end, &walk); > free_vmemmap_page_list(&vmemmap_pages); > } > > but it might overcomplicate things and I am not sure it is any better. > So I am fine with keeping it as is. > Should another user come in the future, we can always revisit. > Maybe just add a little comment in vmemmap_pte_range(), explaining while we > are "+= PAGE_SIZE" for address and I would like to see a comment in > vmemmap_remap_free why the BUG_ON and more important what it is checking. OK, I will add some comments to explain why we do this in vmemmap_remap_free and vmemmap_remap_free. Thanks. > > -- > Oscar Salvador > SUSE L3