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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7B14C433F5 for ; Mon, 21 Mar 2022 20:59:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3CC156B0072; Mon, 21 Mar 2022 16:59:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 37B5F6B0073; Mon, 21 Mar 2022 16:59:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 21CB56B0074; Mon, 21 Mar 2022 16:59:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 144386B0072 for ; Mon, 21 Mar 2022 16:59:18 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id F293D60D57 for ; Mon, 21 Mar 2022 20:59:17 +0000 (UTC) X-FDA: 79269608754.12.BE2B774 Received: from mail-pj1-f54.google.com (mail-pj1-f54.google.com [209.85.216.54]) by imf16.hostedemail.com (Postfix) with ESMTP id 71303180018 for ; Mon, 21 Mar 2022 20:59:17 +0000 (UTC) Received: by mail-pj1-f54.google.com with SMTP id v4so14041307pjh.2 for ; Mon, 21 Mar 2022 13:59:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=IIUq70JYO9LLmND1+BslUpEoL6qaTZK16a7hVYB0QVM=; b=GndI/VxWim9/UZXk2q5afrDqn2qyfiunzh3+1Wi9X8fNS1w85Tf4ChDSAH8lNu5uUL oWYqa/jbEnaFBK81JDNc81tks7HXnDtf3AndRcwvNV9bSWWPsC4XzNwmnBsOEdkY0L1X BSUG7RROwOeVpU/tFDseuWll/YOx3hbAqIOScG1ZrCafa0FxC4cOZFUyKofji/UXVGZE FdsJxWWGaHKc+ZeWwRHhBQEb4MxhvniyoNYzNkXb1HCmR+ZLFFOcLbXYmMAGkuuYqiiQ 4v3yAupeTJUIl3lUpmw43KqO20tcx9Zmm/IP2nvuGgT+hjVlPo1QRaBdT0e2fmiBIXjV tF+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=IIUq70JYO9LLmND1+BslUpEoL6qaTZK16a7hVYB0QVM=; b=ekVQe3yOcFdl80oD3z+/8tyZeAQ82EsYWqDr1NTCNV+Wkj1sr6O076adNwY53aEluU rpgNwv5YVy07NMgHfxvk5vUzSwC8A79isl6dsPGxiZwYNHr/at/fMdmgsMKepgvHJNKx H2tZ7EKfl9VNWS54XLpD9181hdPIwweA2PwHRnd4y+gHRLAcnIPPWEcTHw5/DlvLgUBE MIefRdFbCXzpVFZ7zlXjqKKvTBC2BT5IIgQEwLhiRaLPvWtII+gpElQrYfPPFpynhEAo x89ulzdhcQ0zY410ZKUMwWeP6fATFT1CGhZTFP2k94HMgykzTQBqdIfsMquJ8+aEDLXl zJPA== X-Gm-Message-State: AOAM532rsZR5sVDDwMnFpTRVXSInuj1qurFYhbYhC2qaX6P2O6WTW1Ns iyCOpL/82cYZ4u0GJVbaQPd2HkTiahMvH5a/ZHE= X-Google-Smtp-Source: ABdhPJyBLvSja91CZSb9b1UipjcC7dfke8iT6LTMlxKJcStOuDIKqmTw96VUrfGKcbTdWt/JgXkudAetfH8E4lRL998= X-Received: by 2002:a17:903:124a:b0:151:99fe:1a10 with SMTP id u10-20020a170903124a00b0015199fe1a10mr14532689plh.87.1647896356123; Mon, 21 Mar 2022 13:59:16 -0700 (PDT) MIME-Version: 1.0 References: <20220317234827.447799-1-shy828301@gmail.com> <20220317234827.447799-4-shy828301@gmail.com> In-Reply-To: From: Yang Shi Date: Mon, 21 Mar 2022 13:59:04 -0700 Message-ID: Subject: Re: [v2 PATCH 3/8] mm: khugepaged: skip DAX vma To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Vlastimil Babka , "Kirill A. Shutemov" , Miaohe Lin , Song Liu , Rik van Riel , Matthew Wilcox , Zi Yan , Andrew Morton , "Theodore Ts'o" , Andreas Dilger , darrick.wong@oracle.com, Linux MM , Linux FS-devel Mailing List , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="GndI/VxW"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf16.hostedemail.com: domain of shy828301@gmail.com designates 209.85.216.54 as permitted sender) smtp.mailfrom=shy828301@gmail.com X-Rspamd-Server: rspam03 X-Rspam-User: X-Stat-Signature: dberio993a99fptourbi613nib1etjfe X-Rspamd-Queue-Id: 71303180018 X-HE-Tag: 1647896357-110227 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 Mon, Mar 21, 2022 at 5:04 AM Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote: > > On Thu, Mar 17, 2022 at 04:48:22PM -0700, Yang Shi wrote: > > The DAX vma may be seen by khugepaged when the mm has other khugepaged > > suitable vmas. So khugepaged may try to collapse THP for DAX vma, but > > it will fail due to page sanity check, for example, page is not > > on LRU. > > > > So it is not harmful, but it is definitely pointless to run khugepaged > > against DAX vma, so skip it in early check. > > in fs/xfs/xfs_file.c: > 1391 STATIC int > 1392 xfs_file_mmap( > 1393 struct file *file, > 1394 struct vm_area_struct *vma) > 1395 { > 1396 struct inode *inode = file_inode(file); > 1397 struct xfs_buftarg *target = xfs_inode_buftarg(XFS_I(inode)); > 1398 > 1399 /* > 1400 * We don't support synchronous mappings for non-DAX files and > 1401 * for DAX files if underneath dax_device is not synchronous. > 1402 */ > 1403 if (!daxdev_mapping_supported(vma, target->bt_daxdev)) > 1404 return -EOPNOTSUPP; > 1405 > 1406 file_accessed(file); > 1407 vma->vm_ops = &xfs_file_vm_ops; > 1408 if (IS_DAX(inode)) > 1409 vma->vm_flags |= VM_HUGEPAGE; > > Are xfs and other filesystems setting VM_HUGEPAGE flag even if it can > never be collapsed? DAX is available or intended to use on some special devices, for example, persistent memory. Collapsing huge pages on such devices is not the intended usecase of khugepaged. > > 1410 return 0; > 1411 } > > > > Reviewed-by: Miaohe Lin > > Signed-off-by: Yang Shi > > --- > > mm/khugepaged.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index 82c71c6da9ce..a0e4fa33660e 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -448,6 +448,10 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, > > if (vm_flags & VM_NO_KHUGEPAGED) > > return false; > > > > + /* Don't run khugepaged against DAX vma */ > > + if (vma_is_dax(vma)) > > + return false; > > + > > if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - > > vma->vm_pgoff, HPAGE_PMD_NR)) > > return false; > > -- > > 2.26.3 > > > > > > -- > Thank you, You are awesome! > Hyeonggon :-)