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=-22.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,MISSING_HEADERS, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham 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 B3D7CC433ED for ; Tue, 6 Apr 2021 00:15:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 51786613E8 for ; Tue, 6 Apr 2021 00:15:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 51786613E8 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A49106B0075; Mon, 5 Apr 2021 20:15:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9F8AD6B0078; Mon, 5 Apr 2021 20:15:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8734F6B007B; Mon, 5 Apr 2021 20:15:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 6B27D6B0075 for ; Mon, 5 Apr 2021 20:15:53 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 2EF50180AD83E for ; Tue, 6 Apr 2021 00:15:53 +0000 (UTC) X-FDA: 78000024186.03.541CE74 Received: from mail-lj1-f174.google.com (mail-lj1-f174.google.com [209.85.208.174]) by imf19.hostedemail.com (Postfix) with ESMTP id 429EE90009EA for ; Tue, 6 Apr 2021 00:15:46 +0000 (UTC) Received: by mail-lj1-f174.google.com with SMTP id r20so14438982ljk.4 for ; Mon, 05 Apr 2021 17:15:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:cc; bh=Yp7vvWni51LV8EH8AK8AP/Z8kIvz7Dlwt8s0OEZWhTU=; b=u94Nzhwf1aopm5vCcjdO0RYqds0EHpaKSuc/nLxE5Eu4Qz6VvqUVJthq9kNsrz/7Nf 7OGziOdkgqU/cMgqUujqVxOTwGb32vTkSnGudlsCB8Iv4Itiw/jkHJWNXW/gCovxUiEq bWsIZGVhylzhTe3g4xh81OlJNZ6zZBpz2vx9WyX0oOqRJH+mrJoWaU3VYsoeUP5SHgQQ V/XJIS7v6S3a0MrkAutaFSWBtwXVOdeHhFHEa6PrkgZOTUJOetSEAdclOcAqqun7VRAQ 60O4pl+iPvlD0MQyoZGzPYR6J0riRB8NfPkY1SsdMIorXB3DHlabpFQsmlhOKLZ5F7XN Kaiw== 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:cc; bh=Yp7vvWni51LV8EH8AK8AP/Z8kIvz7Dlwt8s0OEZWhTU=; b=geoDT+mNFySd+nUqVXgt0au9/i4mBp/hw5jfQ+Wc+xFColNfYMxjoE6xv9lToYMczT Dszyzy142NlcIMKidRDs5eyPSlC54Q9pE5rlEzXKwjjtt1agXJS6WrH0kFHLFM8gEFNa DfCcT6n8Syi6NOxrJqKUaNnekDKOYkKhkO/vwW3KpocUdOWLgZMK3VduybuOadOA4Ylz PNv2npoybGZjcFo0o8j2hJvNjVM/0p/hAyFPnUrU2PNHLPSdz8/e3leiKmCpVklz24rg /TG22YDLPKhOCrlMLWxodj+0HB5y2QQAB/XPu9LOGGMRhE7D8Fh6vOni2iaEay1n2IIB 3TOw== X-Gm-Message-State: AOAM532q06Pg8saeB7ojs0a6YyR/x/Cb94xt1qe873XG3B7cpIJD7j5i 06W6AnSjZwsUTktuLQ2MkaI+B2Mgk/lmo5qAoWpktQ== X-Received: by 2002:a2e:b0d0:: with SMTP id g16mt7992675ljl.382.1617668150982; Mon, 05 Apr 2021 17:15:50 -0700 (PDT) MIME-Version: 1.0 References: <20210322215823.962758-1-cfijalkovich@google.com> In-Reply-To: <20210322215823.962758-1-cfijalkovich@google.com> From: Collin Fijalkovich Date: Mon, 5 Apr 2021 17:15:40 -0700 Message-ID: Subject: Re: [PATCH] mm, thp: Relax the VM_DENYWRITE constraint on file-backed THPs Cc: Song Liu , Suren Baghdasaryan , Hridya Valsaraju , Kalesh Singh , Hugh Dickins , Tim Murray , Alexander Viro , Andrew Morton , Linux-Fsdevel , open list , Linux-MM Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 429EE90009EA X-Stat-Signature: ieg3o1t51kr395gbg35dembsiqyhbbpj Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf19; identity=mailfrom; envelope-from=""; helo=mail-lj1-f174.google.com; client-ip=209.85.208.174 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617668146-917079 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: v2 has been uploaded with performance testing results: https://lore.kernel.org/patchwork/patch/1408266/ On Mon, Mar 22, 2021 at 2:59 PM Collin Fijalkovich wrote: > > Transparent huge pages are supported for read-only non-shmem filesystems, > but are only used for vmas with VM_DENYWRITE. This condition ensures that > file THPs are protected from writes while an application is running > (ETXTBSY). Any existing file THPs are then dropped from the page cache > when a file is opened for write in do_dentry_open(). Since sys_mmap > ignores MAP_DENYWRITE, this constrains the use of file THPs to vmas > produced by execve(). > > Systems that make heavy use of shared libraries (e.g. Android) are unable > to apply VM_DENYWRITE through the dynamic linker, preventing them from > benefiting from the resultant reduced contention on the TLB. > > This patch reduces the constraint on file THPs allowing use with any > executable mapping from a file not opened for write (see > inode_is_open_for_write()). It also introduces additional conditions to > ensure that files opened for write will never be backed by file THPs. > > Restricting the use of THPs to executable mappings eliminates the risk that > a read-only file later opened for write would encounter significant > latencies due to page cache truncation. > > The ld linker flag '-z max-page-size=(hugepage size)' can be used to > produce executables with the necessary layout. The dynamic linker must > map these file's segments at a hugepage size aligned vma for the mapping to > be backed with THPs. > > Signed-off-by: Collin Fijalkovich > --- > fs/open.c | 13 +++++++++++-- > mm/khugepaged.c | 16 +++++++++++++++- > 2 files changed, 26 insertions(+), 3 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index e53af13b5835..f76e960d10ea 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -852,8 +852,17 @@ static int do_dentry_open(struct file *f, > * XXX: Huge page cache doesn't support writing yet. Drop all page > * cache for this file before processing writes. > */ > - if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping)) > - truncate_pagecache(inode, 0); > + if (f->f_mode & FMODE_WRITE) { > + /* > + * Paired with smp_mb() in collapse_file() to ensure nr_thps > + * is up to date and the update to i_writecount by > + * get_write_access() is visible. Ensures subsequent insertion > + * of THPs into the page cache will fail. > + */ > + smp_mb(); > + if (filemap_nr_thps(inode->i_mapping)) > + truncate_pagecache(inode, 0); > + } > > return 0; > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index a7d6cb912b05..4c7cc877d5e3 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -459,7 +459,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, > > /* Read-only file mappings need to be aligned for THP to work. */ > if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && > - (vm_flags & VM_DENYWRITE)) { > + !inode_is_open_for_write(vma->vm_file->f_inode) && > + (vm_flags & VM_EXEC)) { > return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, > HPAGE_PMD_NR); > } > @@ -1872,6 +1873,19 @@ static void collapse_file(struct mm_struct *mm, > else { > __mod_lruvec_page_state(new_page, NR_FILE_THPS, nr); > filemap_nr_thps_inc(mapping); > + /* > + * Paired with smp_mb() in do_dentry_open() to ensure > + * i_writecount is up to date and the update to nr_thps is > + * visible. Ensures the page cache will be truncated if the > + * file is opened writable. > + */ > + smp_mb(); > + if (inode_is_open_for_write(mapping->host)) { > + result = SCAN_FAIL; > + __mod_lruvec_page_state(new_page, NR_FILE_THPS, -nr); > + filemap_nr_thps_dec(mapping); > + goto xa_locked; > + } > } > > if (nr_none) { > -- > 2.31.0.rc2.261.g7f71774620-goog >