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 84268C43217 for ; Tue, 1 Mar 2022 09:07:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233653AbiCAJIE (ORCPT ); Tue, 1 Mar 2022 04:08:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233646AbiCAJHx (ORCPT ); Tue, 1 Mar 2022 04:07:53 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A359689CD8; Tue, 1 Mar 2022 01:07:11 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4K7BDc6q0nzdZmq; Tue, 1 Mar 2022 17:05:52 +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; Tue, 1 Mar 2022 17:07:08 +0800 Subject: Re: [PATCH 2/8] mm: khugepaged: remove redundant check for VM_NO_KHUGEPAGED To: Yang Shi CC: , , , , , , , , , , , , , , References: <20220228235741.102941-1-shy828301@gmail.com> <20220228235741.102941-3-shy828301@gmail.com> From: Miaohe Lin Message-ID: <968ccc31-a87c-4657-7193-464f6b5b9259@huawei.com> Date: Tue, 1 Mar 2022 17:07:07 +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: <20220228235741.102941-3-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: dggems701-chm.china.huawei.com (10.3.19.178) 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 hugepage_vma_check() called by khugepaged_enter_vma_merge() does > check VM_NO_KHUGEPAGED. Remove the check from caller and move the check > in hugepage_vma_check() up. > > More checks may be run for VM_NO_KHUGEPAGED vmas, but MADV_HUGEPAGE is > definitely not a hot path, so cleaner code does outweigh. > > Signed-off-by: Yang Shi > --- > mm/khugepaged.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 131492fd1148..82c71c6da9ce 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -366,8 +366,7 @@ int hugepage_madvise(struct vm_area_struct *vma, > * register it here without waiting a page fault that > * may not happen any time soon. > */ > - if (!(*vm_flags & VM_NO_KHUGEPAGED) && > - khugepaged_enter_vma_merge(vma, *vm_flags)) > + if (khugepaged_enter_vma_merge(vma, *vm_flags)) > return -ENOMEM; > break; > case MADV_NOHUGEPAGE: > @@ -446,6 +445,9 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, > if (!transhuge_vma_enabled(vma, vm_flags)) > return false; > > + if (vm_flags & VM_NO_KHUGEPAGED) > + return false; > + This patch does improve the readability. But I have a question. It seems VM_NO_KHUGEPAGED is not checked in the below if-condition: /* Only regular file is valid */ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && (vm_flags & VM_EXEC)) { struct inode *inode = vma->vm_file->f_inode; return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); } If we return false due to VM_NO_KHUGEPAGED here, it seems it will affect the return value of this CONFIG_READ_ONLY_THP_FOR_FS condition check. Or am I miss something? Thanks. > if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - > vma->vm_pgoff, HPAGE_PMD_NR)) > return false; > @@ -471,7 +473,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, > return false; > if (vma_is_temporary_stack(vma)) > return false; > - return !(vm_flags & VM_NO_KHUGEPAGED); > + > + return true; > } > > int __khugepaged_enter(struct mm_struct *mm) >