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=unavailable 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 83ACFC433DF for ; Fri, 17 Jul 2020 15:54:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F31B204EA for ; Fri, 17 Jul 2020 15:54:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726399AbgGQPyB (ORCPT ); Fri, 17 Jul 2020 11:54:01 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:54463 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726344AbgGQPyA (ORCPT ); Fri, 17 Jul 2020 11:54:00 -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 06HFrxBQ029543 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 17 Jul 2020 11:53:59 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id CD1D2420478; Fri, 17 Jul 2020 11:53:58 -0400 (EDT) From: "Theodore Ts'o" To: Ext4 Developers List Cc: Alex Zhuravlev , Alex Zhuravlev , Andreas Dilger Subject: [PATCH 2/4] ext4: skip non-loaded groups at cr=0/1 when scanning for good groups Date: Fri, 17 Jul 2020 11:53:50 -0400 Message-Id: <20200717155352.1053040-3-tytso@mit.edu> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200717155352.1053040-1-tytso@mit.edu> References: <20200717155352.1053040-1-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 store 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. 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 --- fs/ext4/mballoc.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 8a1e6e03c088..172994349bf6 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2195,7 +2195,18 @@ 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 */ + if (cr < 2 && + !(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