From patchwork Mon May 1 12:43:35 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josef Bacik X-Patchwork-Id: 9706447 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8A39C60387 for ; Mon, 1 May 2017 12:43:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6E32922638 for ; Mon, 1 May 2017 12:43:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 60B5B28066; Mon, 1 May 2017 12:43:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.4 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D9FC522638 for ; Mon, 1 May 2017 12:43:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423725AbdEAMnj (ORCPT ); Mon, 1 May 2017 08:43:39 -0400 Received: from mail-qt0-f193.google.com ([209.85.216.193]:34537 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423251AbdEAMni (ORCPT ); Mon, 1 May 2017 08:43:38 -0400 Received: by mail-qt0-f193.google.com with SMTP id y33so16312312qta.1 for ; Mon, 01 May 2017 05:43:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toxicpanda-com.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id; bh=WQ6pStaMyjiJrkBtorQmobod0ysypvnBqmMXyGCiyj4=; b=n24SMCIi+aHrSph4F9yEdJP5Hv9BKWyCibMtQehxzEe1obrll0ms7o+iZyIIbkX4sN UzPUs+9G/YFq7VIp7sj7PtpGN0vn0xBXOhZE5dtdUd85dEUGuBRaWeIUSCRXRLrKfDFB LlT6ozuPdQ2uWWGBbUb9RaSnmK+DU5OdkLShYXOdL32K63NeIh7fVAn965RA0EQTVBQx QJpcUf2eCoMB8rAZbrKMslwTFLUeTbXfR+RGF7Gr7c1wxB8HhLVG/RTksjxd5pWKDNnE /0PJrd7lFsXF22kUenbuBPyLtpO8/VRSlgIGo3zZLrAgaC1qByGxWUhRbJVp6uz+Wo1V 8sZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id; bh=WQ6pStaMyjiJrkBtorQmobod0ysypvnBqmMXyGCiyj4=; b=mdkTQC49BA5Q+OlbnCw/kxYeFcBBoWTrKcHqnXzGF2tZAFbqzgi+F0yczgqj4+eAlM DmBABddLk3F1YF4QwU01GH0Z4BOeHyXVgiithu33btpIhaBa7dl1DyrNkp7/8leqim+u +Fn8JjLJXZ1zbpA4xPQFWXf9rKCsnGtjC4oDbiaaGO+NA1sADIviKazfJ3EB2c4azoYc H9OjEcS8swq7cIOBLDxtOH9YPq67hnWE6CvTljpmZz3AO3pxp83mlOcnk4WR5bHnPMr/ 5m9Js1w8ELjbQY3+qySFmlt/ZqqltnkJggh1df2CHtWFYIkW3BbULwR1AxDzotfM20P5 igjA== X-Gm-Message-State: AN3rC/7Bp3wJFeitjzoORB93fTcRackgtMzgB2iy28/z98jlNvFkTa+j FR9gEmyge3U0wQ== X-Received: by 10.237.35.162 with SMTP id j31mr21017193qtc.117.1493642617111; Mon, 01 May 2017 05:43:37 -0700 (PDT) Received: from localhost ([2606:a000:4381:1201:225:22ff:feb3:e51a]) by smtp.gmail.com with ESMTPSA id q95sm9212765qkq.22.2017.05.01.05.43.36 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 May 2017 05:43:36 -0700 (PDT) From: Josef Bacik X-Google-Original-From: Josef Bacik To: viro@ZenIV.linux.org.uk, linux-fsdevel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH][RESEND] fs: don't set *REFERENCED on single use objects Date: Mon, 1 May 2017 08:43:35 -0400 Message-Id: <1493642615-26881-1-git-send-email-jbacik@fb.com> X-Mailer: git-send-email 2.7.4 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP By default we set DCACHE_REFERENCED and I_REFERENCED on any dentry or inode we create. This is problematic as this means that it takes two trips through the LRU for any of these objects to be reclaimed, regardless of their actual lifetime. With enough pressure from these caches we can easily evict our working set from page cache with single use objects. So instead only set *REFERENCED if we've already been added to the LRU list. This means that we've been touched since the first time we were accessed, and so more likely to need to hang out in cache. To illustrate this issue I wrote the following scripts https://github.com/josefbacik/debug-scripts/tree/master/cache-pressure on my test box. It is a single socket 4 core CPU with 16gib of RAM and I tested on an Intel 2tib NVME drive. The cache-pressure.sh script creates a new file system and creates 2 6.5gib files in order to take up 13gib of the 16gib of ram with pagecache. Then it runs a test program that reads these 2 files in a loop, and keeps track of how often it has to read bytes for each loop. On an ideal system with no pressure we should have to read 0 bytes indefinitely. The second thing this script does is start a fs_mark job that creates a ton of 0 length files, putting pressure on the system with slab only allocations. On exit the script prints out how many bytes were read by the read-file program. The results are as follows Without patch: /mnt/btrfs-test/reads/file1: total read during loops 27262988288 /mnt/btrfs-test/reads/file2: total read during loops 27262976000 With patch: /mnt/btrfs-test/reads/file2: total read during loops 18640457728 /mnt/btrfs-test/reads/file1: total read during loops 9565376512 This patch results in a 50% reduction of the amount of pages evicted from our working set. Reviewed-by: Jan Kara Signed-off-by: Josef Bacik --- fs/dcache.c | 4 ++-- fs/inode.c | 3 ++- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index 95d71ed..cddf397 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -419,6 +419,8 @@ static void dentry_lru_add(struct dentry *dentry) { if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) d_lru_add(dentry); + else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED))) + dentry->d_flags |= DCACHE_REFERENCED; } /** @@ -779,8 +781,6 @@ void dput(struct dentry *dentry) goto kill_it; } - if (!(dentry->d_flags & DCACHE_REFERENCED)) - dentry->d_flags |= DCACHE_REFERENCED; dentry_lru_add(dentry); dentry->d_lockref.count--; diff --git a/fs/inode.c b/fs/inode.c index 88110fd..9dfa8f1 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -405,6 +405,8 @@ static void inode_lru_list_add(struct inode *inode) { if (list_lru_add(&inode->i_sb->s_inode_lru, &inode->i_lru)) this_cpu_inc(nr_unused); + else + inode->i_state |= I_REFERENCED; } /* @@ -1492,7 +1494,6 @@ static void iput_final(struct inode *inode) drop = generic_drop_inode(inode); if (!drop && (sb->s_flags & MS_ACTIVE)) { - inode->i_state |= I_REFERENCED; inode_add_lru(inode); spin_unlock(&inode->i_lock); return;