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 03507C433F5 for ; Wed, 2 Mar 2022 18:43:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 51CFD8D0002; Wed, 2 Mar 2022 13:43:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4CD4E8D0001; Wed, 2 Mar 2022 13:43:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3951C8D0002; Wed, 2 Mar 2022 13:43:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0083.hostedemail.com [216.40.44.83]) by kanga.kvack.org (Postfix) with ESMTP id 2A8B38D0001 for ; Wed, 2 Mar 2022 13:43:45 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id D99958249980 for ; Wed, 2 Mar 2022 18:43:44 +0000 (UTC) X-FDA: 79200319968.28.D54AA1D Received: from mail-ej1-f53.google.com (mail-ej1-f53.google.com [209.85.218.53]) by imf03.hostedemail.com (Postfix) with ESMTP id 39B3B20009 for ; Wed, 2 Mar 2022 18:43:44 +0000 (UTC) Received: by mail-ej1-f53.google.com with SMTP id a8so5617264ejc.8 for ; Wed, 02 Mar 2022 10:43:43 -0800 (PST) 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=MYacYFBXciHmpzBVvSdoS7PTXsJUtBNkCcTgWfD2hXg=; b=IirjpbFJTyj19jcvRBrG6M2PJAxHcjEHQfbNn3mOZadb1e1ccHA/LRrHk1rksJpt35 MMt2dm7wSSrSlQQTxI44MM0nypv3syVFTI5nsJPKjrZqprWNhtUpFBqSmN7jueiuRM9O nM1/br4YMIBeEaR/nknarhnm2LTZnxp8rxb9jOgLVboCFtdMZok9gz9GuCPYUoA0jX+N IcsILGgEFTzGaOtAw+W4jNLvqf2OCbQ2R+153snnJ8Ltdo/8MshR/5j02p+VlkM+E33r J0KpTmjs0vzUF2pWRa2+W654eN+vr/n+pXKZMBNudNlOAfIqSM9ZhZzjnl51p3wTxGZy tlLA== 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=MYacYFBXciHmpzBVvSdoS7PTXsJUtBNkCcTgWfD2hXg=; b=7zaAwYDnJJvJIvx4VXpCWIojF9M7rKlzSICR3pDtr1u9IO5d6etlFbzFjo4mHxioGY UjmQSoXUPAK5IsKmhJsh6iCMkunqyKwdOJ/MAJ7Fq6cqbQjMdIoK8gjWtk6Q0jwy91cy spO+0NUNuwDpmFVLJv1du/WpUD5T/NBpe6XApBcLMswEn2yDeCdsBHqrw++Kwme9LhmZ Q984QQxS+c11NgNKKf1G70kMirN7vkcL+vgp38fVeW9Ldirz+hsQ57J7aABztYRm1AmE JFBI+hDB+wU8s0ZvNaGAlGjM6EfBFC1ljiwaYFtPDRMKmGi2vSCayenIa4lJMNIH500E YHvA== X-Gm-Message-State: AOAM530JxW/ZVI240ryXFHEhXSJ1Usdev2e6h6flIfq8YtXhF4miFxa5 8w2S3BkfYd5yxgFxJionEuuGV2gRsk+VKd6LPaU= X-Google-Smtp-Source: ABdhPJyuYRtx7NDrJEc4gq8pmV8JxkyEHirpVjET0jmaEbM8g2xi3VgPWfm3DCWICSOT7fYRWup0wjnZgNE081ucq84= X-Received: by 2002:a17:906:e28a:b0:6d6:e2e9:d39d with SMTP id gg10-20020a170906e28a00b006d6e2e9d39dmr8101292ejb.2.1646246622894; Wed, 02 Mar 2022 10:43:42 -0800 (PST) MIME-Version: 1.0 References: <20220228235741.102941-1-shy828301@gmail.com> <20220228235741.102941-3-shy828301@gmail.com> <968ccc31-a87c-4657-7193-464f6b5b9259@huawei.com> In-Reply-To: <968ccc31-a87c-4657-7193-464f6b5b9259@huawei.com> From: Yang Shi Date: Wed, 2 Mar 2022 10:43:31 -0800 Message-ID: Subject: Re: [PATCH 2/8] mm: khugepaged: remove redundant check for VM_NO_KHUGEPAGED To: Miaohe Lin Cc: Linux MM , Linux FS-devel Mailing List , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, Linux Kernel Mailing List , Vlastimil Babka , "Kirill A. Shutemov" , Song Liu , Rik van Riel , Matthew Wilcox , Zi Yan , Andrew Morton , "Theodore Ts'o" , Andreas Dilger , darrick.wong@oracle.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 39B3B20009 X-Stat-Signature: grzad14u1fcd77cb5ynozr4p4hxo1xr6 X-Rspam-User: Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=IirjpbFJ; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf03.hostedemail.com: domain of shy828301@gmail.com designates 209.85.218.53 as permitted sender) smtp.mailfrom=shy828301@gmail.com X-Rspamd-Server: rspam03 X-HE-Tag: 1646246624-204330 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 Tue, Mar 1, 2022 at 1:07 AM Miaohe Lin wrote: > > 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? Yes, it will return false instead of true if that file THP check is true, but wasn't that old behavior actually problematic? Khugepaged definitely can't collapse VM_NO_KHUGEPAGED vmas even though it satisfies all the readonly file THP checks. With the old behavior khugepaged may scan an exec file hugetlb vma IIUC although it will fail later due to other page sanity checks, i.e. page compound check. > > 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) > > > >