From nobody Thu Oct 9 01:13:38 2025 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (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 DFC241F6667; Mon, 23 Jun 2025 07:47:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750664823; cv=none; b=kq/2A9mQHKjbZLP1llrfxru6VATpX8POQMAFywdUtndcuTxA9D8RyswZO4ppjdDpFyY5QqmGqx7LICNfLQhlwddG2zbBd1Bvg9zCBCE8U4+c56P8j4f1HE/FqOg13RDzO3IDWITEIquXhwrKny6pJg1BRzJ2sCh8k0eaRgI+7Vo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750664823; c=relaxed/simple; bh=sYtqUFt4brvDA+yF4dcv6k3g1PaR0DyYG66HfGgJ7PQ=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UuW4p3KOhL2MRSlJzjrTcz8K4IDeJM/aYz5AAAQXfuRcRaIh6vjD4j/scx+d7QG7fJa6G5aFTsrL9/Y2bfkI59UYMu5+jHZrO/6UwFMtHIynf9a1LZHu/X1v/N7ud2wi5sBSeb91+WNnaVK1fHptKzoDoTT87JGeIwUDVnmZTcs= 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=45.249.212.190 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 [172.19.162.112]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4bQg9H39fFz2TSJG; 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 1A0501401F2; Mon, 23 Jun 2025 15:46:58 +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 15:46:57 +0800 From: Baokun Li To: CC: , , , , , , , Subject: [PATCH v2 04/16] ext4: utilize multiple global goals to reduce contention Date: Mon, 23 Jun 2025 15:32:52 +0800 Message-ID: <20250623073304.3275702-5-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-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To dggpemf500013.china.huawei.com (7.185.36.188) When allocating data blocks, if the first try (goal allocation) fails and stream allocation is on, it tries a global goal starting from the last group we used (s_mb_last_group). This helps cluster large files together to reduce free space fragmentation, and the data block contiguity also accelerates write-back to disk. However, when multiple processes allocate blocks,=C2=A0having just one glob= al goal means they all fight over the same group. This drastically lowers the chances of extents merging and leads to much worse file fragmentation. To mitigate this multi-process contention, we now employ multiple global goals, with the number of goals being the CPU count rounded up to the nearest power of 2. To ensure a consistent goal for each inode, we select the corresponding goal by taking the inode number modulo the total number of goals. 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 | 7612 | 19699 (+158%) | 21647 | 53093 (+145%) | mb_optimize_scan=3D1 | 7568 | 9862 (+30.3%) | 9117 | 14401 (+57.9%) | Signed-off-by: Baokun Li --- fs/ext4/ext4.h | 2 +- fs/ext4/mballoc.c | 31 ++++++++++++++++++++++++------- fs/ext4/mballoc.h | 9 +++++++++ 3 files changed, 34 insertions(+), 8 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 93f03d8c3dca..c3f16aba7b79 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 */ - ext4_group_t s_mb_last_group; + ext4_group_t *s_mb_last_groups; 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 3f103919868b..216b332a5054 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2168,9 +2168,12 @@ 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) - /* pairs with smp_load_acquire in ext4_mb_regular_allocator() */ - smp_store_release(&sbi->s_mb_last_group, ac->ac_f_ex.fe_group); + if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) { + int hash =3D ac->ac_inode->i_ino % MB_LAST_GROUPS; + /* Pairs with smp_load_acquire in ext4_mb_regular_allocator() */ + smp_store_release(&sbi->s_mb_last_groups[hash], + ac->ac_f_ex.fe_group); + } /* * As we've just preallocated more space than * user requested originally, we store allocated @@ -2842,9 +2845,12 @@ 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) - /* 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); + if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) { + int hash =3D ac->ac_inode->i_ino % MB_LAST_GROUPS; + /* 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_groups[hash]); + } =20 /* * Let's just scan groups to find more-less suitable blocks We @@ -3715,10 +3721,17 @@ int ext4_mb_init(struct super_block *sb) sbi->s_mb_group_prealloc, EXT4_NUM_B2C(sbi, sbi->s_stripe)); } =20 + sbi->s_mb_last_groups =3D kcalloc(MB_LAST_GROUPS, sizeof(ext4_group_t), + GFP_KERNEL); + if (sbi->s_mb_last_groups =3D=3D NULL) { + ret =3D -ENOMEM; + goto out; + } + sbi->s_locality_groups =3D alloc_percpu(struct ext4_locality_group); if (sbi->s_locality_groups =3D=3D NULL) { ret =3D -ENOMEM; - goto out; + goto out_free_last_groups; } for_each_possible_cpu(i) { struct ext4_locality_group *lg; @@ -3743,6 +3756,9 @@ int ext4_mb_init(struct super_block *sb) out_free_locality_groups: free_percpu(sbi->s_locality_groups); sbi->s_locality_groups =3D NULL; +out_free_last_groups: + kvfree(sbi->s_mb_last_groups); + sbi->s_mb_last_groups =3D NULL; out: kfree(sbi->s_mb_avg_fragment_size); kfree(sbi->s_mb_avg_fragment_size_locks); @@ -3847,6 +3863,7 @@ void ext4_mb_release(struct super_block *sb) } =20 free_percpu(sbi->s_locality_groups); + kvfree(sbi->s_mb_last_groups); } =20 static inline int ext4_issue_discard(struct super_block *sb, diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h index f8280de3e882..38c37901728d 100644 --- a/fs/ext4/mballoc.h +++ b/fs/ext4/mballoc.h @@ -97,6 +97,15 @@ */ #define MB_NUM_ORDERS(sb) ((sb)->s_blocksize_bits + 2) =20 +/* + * Number of mb last groups + */ +#ifdef CONFIG_SMP +#define MB_LAST_GROUPS roundup_pow_of_two(nr_cpu_ids) +#else +#define MB_LAST_GROUPS 1 +#endif + struct ext4_free_data { /* this links the free block information from sb_info */ struct list_head efd_list; --=20 2.46.1