From nobody Thu Oct 9 01:11:32 2025 Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B52581388; Mon, 23 Jun 2025 07:47:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.191 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750664823; cv=none; b=mc4enlcAOb+wgeaFIj3kSjSIGyVoXLgI9fRo2EcwJWBdYdQ1FTQUKe8D5qxvF2FSsBDeVhYqYhXM3/5vGCAsPbCsOebStIxrZOm5VfrFRDLwO5ALqX0/iA6TP7QZto19/WJKhq0/tKDy/H2ySk3oNeujyLUYL+kBHLfPC4hNy1s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750664823; c=relaxed/simple; bh=jsK+9dugOTCQLSNIxqMiLiZ14gIE22FtPTOf9JWnmqM=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=EE7A2f/+bGO2BfbOVQx99wU8kV98UKoCOsRNr5rFpAdGt/2oYdgXvb5lPOJNff/JgmxhvLHJgf6ePG77Wk5EmVFvHMBhtL6PvsAQxTfCKvQkH4MHRiP9HUrgMQO0g5MMJj21q8aygczFUrDtgIM4hB/8QVQebfXbcR+RUMHgk64= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.191 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.17]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4bQg9H0Rcvz2BdVh; Mon, 23 Jun 2025 15:45:23 +0800 (CST) Received: from dggpemf500013.china.huawei.com (unknown [7.185.36.188]) by mail.maildlp.com (Postfix) with ESMTPS id 3AA441A0188; Mon, 23 Jun 2025 15:46:57 +0800 (CST) Received: from huawei.com (10.175.112.188) by dggpemf500013.china.huawei.com (7.185.36.188) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 23 Jun 2025 15:46:56 +0800 From: Baokun Li To: CC: , , , , , , , Subject: [PATCH v2 03/16] ext4: remove unnecessary s_md_lock on update s_mb_last_group Date: Mon, 23 Jun 2025 15:32:51 +0800 Message-ID: <20250623073304.3275702-4-libaokun1@huawei.com> X-Mailer: git-send-email 2.46.1 In-Reply-To: <20250623073304.3275702-1-libaokun1@huawei.com> References: <20250623073304.3275702-1-libaokun1@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To dggpemf500013.china.huawei.com (7.185.36.188) Content-Type: text/plain; charset="utf-8" After we optimized the block group lock, we found another lock contention issue when running will-it-scale/fallocate2 with multiple processes. The fallocate's block allocation and the truncate's block release were fighting over the s_md_lock. The problem is, this lock protects totally different things in those two processes: the list of freed data blocks (s_freed_data_list) when releasing, and where to start looking for new blocks (mb_last_group) when allocating. Now we only need to track s_mb_last_group and no longer need to track s_mb_last_start, so we don't need the s_md_lock lock to ensure that the two are consistent, and we can ensure that the s_mb_last_group read is up to date by using smp_store_release/smp_load_acquire. Besides, the s_mb_last_group data type only requires ext4_group_t (i.e., unsigned int), rendering unsigned long superfluous. Performance test data follows: Test: Running will-it-scale/fallocate2 on CPU-bound containers. Observation: Average fallocate operations per container per second. | Kunpeng 920 / 512GB -P80| AMD 9654 / 1536GB -P96 | Disk: 960GB SSD |-------------------------|-------------------------| | base | patched | base | patched | -------------------|-------|-----------------|-------|-----------------| mb_optimize_scan=3D0 | 4821 | 7612 (+57.8%) | 15371 | 21647 (+40.8%) | mb_optimize_scan=3D1 | 4784 | 7568 (+58.1%) | 6101 | 9117 (+49.4%) | Signed-off-by: Baokun Li --- fs/ext4/ext4.h | 2 +- fs/ext4/mballoc.c | 17 ++++++----------- 2 files changed, 7 insertions(+), 12 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index cfb60f8fbb63..93f03d8c3dca 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1630,7 +1630,7 @@ struct ext4_sb_info { unsigned int s_mb_group_prealloc; unsigned int s_max_dir_size_kb; /* where last allocation was done - for stream allocation */ - unsigned long s_mb_last_group; + ext4_group_t s_mb_last_group; unsigned int s_mb_prefetch; unsigned int s_mb_prefetch_limit; unsigned int s_mb_best_avail_max_trim_order; diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 5cdae3bda072..3f103919868b 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2168,11 +2168,9 @@ static void ext4_mb_use_best_found(struct ext4_alloc= ation_context *ac, ac->ac_buddy_folio =3D e4b->bd_buddy_folio; folio_get(ac->ac_buddy_folio); /* store last allocated for subsequent stream allocation */ - if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) { - spin_lock(&sbi->s_md_lock); - sbi->s_mb_last_group =3D ac->ac_f_ex.fe_group; - spin_unlock(&sbi->s_md_lock); - } + if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) + /* pairs with smp_load_acquire in ext4_mb_regular_allocator() */ + smp_store_release(&sbi->s_mb_last_group, ac->ac_f_ex.fe_group); /* * As we've just preallocated more space than * user requested originally, we store allocated @@ -2844,12 +2842,9 @@ ext4_mb_regular_allocator(struct ext4_allocation_con= text *ac) } =20 /* if stream allocation is enabled, use global goal */ - if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) { - /* TBD: may be hot point */ - spin_lock(&sbi->s_md_lock); - ac->ac_g_ex.fe_group =3D sbi->s_mb_last_group; - spin_unlock(&sbi->s_md_lock); - } + if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) + /* pairs with smp_store_release in ext4_mb_use_best_found() */ + ac->ac_g_ex.fe_group =3D smp_load_acquire(&sbi->s_mb_last_group); =20 /* * Let's just scan groups to find more-less suitable blocks We --=20 2.46.1