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 184ADC433F5 for ; Tue, 7 Dec 2021 01:17:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344778AbhLGBUw (ORCPT ); Mon, 6 Dec 2021 20:20:52 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:60582 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344156AbhLGBUu (ORCPT ); Mon, 6 Dec 2021 20:20:50 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id EC28E1FD5C for ; Tue, 7 Dec 2021 01:17:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1638839839; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Wj08J1JUEkAQtNBbJ0Q+HDExeM67BRcSPk8IGeqR1Rc=; b=QePYry1PgU+MVJSHy6Gdh8VjaHe/E30SQy9PltWjzqVdfWQSXH+ATWnlv05koOoD61L4vc j1KFuOgGwFsFFqjSxNkNn34XPGFWHkhjIPeZRmQa9NeqoTSAlyAQPsoUO5oK2+Vk2/Gqz9 +9LUCgV6f7yEIziXUz0lzQYO+NKWFHI= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3C56613A5C for ; Tue, 7 Dec 2021 01:17:19 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id aG3YAR+2rmE8LQAAMHmgww (envelope-from ) for ; Tue, 07 Dec 2021 01:17:19 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v2 5/5] btrfs: skip subtree scan if it's too high to avoid low stall in btrfs_commit_transaction() Date: Tue, 7 Dec 2021 09:16:55 +0800 Message-Id: <20211207011655.21579-6-wqu@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211207011655.21579-1-wqu@suse.com> References: <20211207011655.21579-1-wqu@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Btrfs qgroup has a long history of bringing performance penalty in btrfs_commit_transaction(). Although we tried our best to migrate such impact, there is still an unsolved call site, btrfs_drop_snapshot(). This function will find the highest shared tree block and modify its extent ownership to do a subvolume/snapshot dropping. Such change will affect the whole subtree, and cause tons of qgroup dirty extents and stall btrfs_commit_transaction(). To avoid such problem, here we introduce a new sysfs interface, /sys/fs/btrfs//qgroups/drop_subptree_threshold, to determine at whether and at which level we should skip qgroup accounting for subtree dropping. The default value is BTRFS_MAX_LEVEL, thus every subtree drop will go through qgroup accounting, to ensure qgroup numbers are kept as consistent as possible. While for performance sensitive users, they can change the values to more reasonable values like 3, to make any subtree, which is at or higher than level 3, to mark qgroup inconsistent and skip the accounting. The cost is obvious, the qgroup number is no longer consistent, but at least performance is more reasonable, and users have the control. Signed-off-by: Qu Wenruo --- fs/btrfs/ctree.h | 1 + fs/btrfs/disk-io.c | 1 + fs/btrfs/qgroup.c | 18 ++++++++++++++++++ fs/btrfs/sysfs.c | 39 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 59 insertions(+) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index dfee4b403da1..79512a0f6a5b 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -952,6 +952,7 @@ struct btrfs_fs_info { struct completion qgroup_rescan_completion; struct btrfs_work qgroup_rescan_work; bool qgroup_rescan_running; /* protected by qgroup_rescan_lock */ + u8 qgroup_drop_subtree_thres; /* filesystem state */ unsigned long fs_state; diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 5c598e124c25..a5167de302e8 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2385,6 +2385,7 @@ static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info) fs_info->qgroup_seq = 1; fs_info->qgroup_ulist = NULL; fs_info->qgroup_rescan_running = false; + fs_info->qgroup_drop_subtree_thres = BTRFS_MAX_LEVEL; mutex_init(&fs_info->qgroup_rescan_lock); } diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index 6977ce093993..0d89c0dfd67d 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1230,6 +1230,7 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) quota_root = fs_info->quota_root; fs_info->quota_root = NULL; fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_ON; + fs_info->qgroup_drop_subtree_thres = BTRFS_MAX_LEVEL; spin_unlock(&fs_info->qgroup_lock); btrfs_free_qgroup_config(fs_info); @@ -2258,6 +2259,7 @@ int btrfs_qgroup_trace_subtree(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info = trans->fs_info; int ret = 0; int level; + u8 drop_subptree_thres; struct extent_buffer *eb = root_eb; struct btrfs_path *path = NULL; @@ -2267,6 +2269,22 @@ int btrfs_qgroup_trace_subtree(struct btrfs_trans_handle *trans, if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) return 0; + spin_lock(&fs_info->qgroup_lock); + drop_subptree_thres = fs_info->qgroup_drop_subtree_thres; + spin_unlock(&fs_info->qgroup_lock); + /* + * This function only get called for snapshot drop, if we hit a high + * node here, it means we are going to change ownership for quite a lot + * of extents, which will greatly slow down btrfs_commit_transaction(). + * + * So here if we find a high tree here, we just skip the accounting and + * mark qgroup inconsistent. + */ + if (root_level >= drop_subptree_thres) { + qgroup_mark_inconsistent(fs_info); + return 0; + } + if (!extent_buffer_uptodate(root_eb)) { ret = btrfs_read_buffer(root_eb, root_gen, root_level, NULL); if (ret) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index e48904666703..7bc9906ecbfa 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -1857,6 +1857,44 @@ static ssize_t qgroup_inconsistent_show(struct kobject *qgroups_kobj, BTRFS_ATTR(qgroups, inconsistent, qgroup_inconsistent_show); +static ssize_t qgroup_drop_subtree_thres_show(struct kobject *qgroups_kobj, + struct kobj_attribute *a, + char *buf) +{ + struct btrfs_fs_info *fs_info = to_fs_info(qgroups_kobj->parent); + u8 result; + + spin_lock(&fs_info->qgroup_lock); + result = fs_info->qgroup_drop_subtree_thres; + spin_unlock(&fs_info->qgroup_lock); + + return scnprintf(buf, PAGE_SIZE, "%d\n", result); +} + +static ssize_t qgroup_drop_subtree_thres_store(struct kobject *qgroups_kobj, + struct kobj_attribute *a, + const char *buf, size_t len) +{ + struct btrfs_fs_info *fs_info = to_fs_info(qgroups_kobj->parent); + u8 new_thres; + int ret; + + ret = kstrtou8(buf, 10, &new_thres); + if (ret) + return -EINVAL; + + if (new_thres > BTRFS_MAX_LEVEL) + return -EINVAL; + + spin_lock(&fs_info->qgroup_lock); + fs_info->qgroup_drop_subtree_thres = new_thres; + spin_unlock(&fs_info->qgroup_lock); + return len; +} + +BTRFS_ATTR_RW(qgroups, drop_subtree_threshold, qgroup_drop_subtree_thres_show, + qgroup_drop_subtree_thres_store); + /* * Qgroups global info * @@ -1865,6 +1903,7 @@ BTRFS_ATTR(qgroups, inconsistent, qgroup_inconsistent_show); static struct attribute *qgroups_attrs[] = { BTRFS_ATTR_PTR(qgroups, enabled), BTRFS_ATTR_PTR(qgroups, inconsistent), + BTRFS_ATTR_PTR(qgroups, drop_subtree_threshold), NULL }; ATTRIBUTE_GROUPS(qgroups); -- 2.34.1