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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 284F9C433E3 for ; Fri, 31 Jul 2020 19:08:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 140EE21744 for ; Fri, 31 Jul 2020 19:08:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729910AbgGaTId (ORCPT ); Fri, 31 Jul 2020 15:08:33 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:59743 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728713AbgGaTId (ORCPT ); Fri, 31 Jul 2020 15:08:33 -0400 Received: from callcc.thunk.org (pool-96-230-252-158.bstnma.fios.verizon.net [96.230.252.158]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 06VJ8SdU009106 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 31 Jul 2020 15:08:29 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 5C343420478; Fri, 31 Jul 2020 15:08:28 -0400 (EDT) From: "Theodore Ts'o" To: Ext4 Developers List Cc: Alex Zhuravlev , Andreas Dilger , Artem Blagodarenko Subject: [PATCH 2/4] ext4: skip non-loaded groups at cr=0/1 when scanning for good groups Date: Fri, 31 Jul 2020 15:08:03 -0400 Message-Id: <20200731190805.181253-3-tytso@mit.edu> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200731190805.181253-1-tytso@mit.edu> References: <20200731190805.181253-1-tytso@mit.edu> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org From: Alex Zhuravlev cr=0 is supposed to be an optimization to save CPU cycles, but if buddy data (in memory) is not initialized then all this makes no sense as we have to do sync IO taking a lot of cycles. Also, at cr=0 mballoc doesn't choose any avaibale chunk. cr=1 also skips groups using heuristic based on avg. fragment size. It's more useful to skip such groups and switch to cr=2 where groups will be scanned for available chunks. However, we always read the first block group in a flex_bg so metadata blocks will get read into the first flex_bg if possible. Using sparse image and dm-slow virtual device of 120TB was simulated, then the image was formatted and filled using debugfs to mark ~85% of available space as busy. mount process w/o the patch couldn't complete in half an hour (according to vmstat it would take ~10-11 hours). With the patch applied mount took ~20 seconds. Lustre-bug-id: https://jira.whamcloud.com/browse/LU-12988 Signed-off-by: Alex Zhuravlev Reviewed-by: Andreas Dilger Reviewed-by: Artem Blagodarenko --- fs/ext4/mballoc.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index fcc702f1ff15..b1ef35a9e9f1 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2177,6 +2177,7 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac, { struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group); struct super_block *sb = ac->ac_sb; + struct ext4_sb_info *sbi = EXT4_SB(sb); bool should_lock = ac->ac_flags & EXT4_MB_STRICT_CHECK; ext4_grpblk_t free; int ret = 0; @@ -2195,7 +2196,26 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac, /* We only do this if the grp has never been initialized */ if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) { - ret = ext4_mb_init_group(ac->ac_sb, group, GFP_NOFS); + struct ext4_group_desc *gdp = + ext4_get_group_desc(sb, group, NULL); + int ret; + + /* cr=0/1 is a very optimistic search to find large + * good chunks almost for free. If buddy data is not + * ready, then this optimization makes no sense. But + * we never skip the first block group in a flex_bg, + * since this gets used for metadata block allocation, + * and we want to make sure we locate metadata blocks + * in the first block group in the flex_bg if + * possible. + */ + if (cr < 2 && + (!sbi->s_log_groups_per_flex || + ((group & ((1 << sbi->s_log_groups_per_flex) - 1)) != 0)) && + !(ext4_has_group_desc_csum(sb) && + (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)))) + return 0; + ret = ext4_mb_init_group(sb, group, GFP_NOFS); if (ret) return ret; } -- 2.24.1