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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 011ECC43219 for ; Wed, 2 Mar 2022 03:21:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239301AbiCBDVz (ORCPT ); Tue, 1 Mar 2022 22:21:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230473AbiCBDVx (ORCPT ); Tue, 1 Mar 2022 22:21:53 -0500 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53284B0A51; Tue, 1 Mar 2022 19:21:10 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4K7fR10Lj5z1GC0v; Wed, 2 Mar 2022 11:16:29 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 2 Mar 2022 11:21:07 +0800 Subject: Re: [PATCH 3/8] mm: khugepaged: skip DAX vma To: Yang Shi CC: , , , , , , , , , , , , , , References: <20220228235741.102941-1-shy828301@gmail.com> <20220228235741.102941-4-shy828301@gmail.com> From: Miaohe Lin Message-ID: <6177c880-a34e-2539-764a-0de38c0cbc11@huawei.com> Date: Wed, 2 Mar 2022 11:21:07 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220228235741.102941-4-shy828301@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/3/1 7:57, 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. Yep. There is PageLRU check in khugepaged_scan_{file,pmd}. > > So it is not harmful, but it is definitely pointless to run khugepaged > against DAX vma, so skip it in early check. > This patch looks good to me. Thanks. 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; >