From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) (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 3542E23DE; Sat, 19 Jul 2025 00:37:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752885478; cv=none; b=GBkOZVrASg6XwU5onC/JOA4HYzD7oqT84mLi+XWlO3VnJ10pmnVW/PRfdzPH68K6ciuRjA4eAnSUnBeN/IpDoddw2WjIODBygkh8444zNzWuBq+Ku+wMNYHc+bL6MNuC95dg46xjsCZE/Me9dHJdK1heH629xff7ToMcLaA0hSo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752885478; c=relaxed/simple; bh=iHuRoaqiqgLMa15x4TcvHU/rCSRoHuJ3bjn6cbUe/7E=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=mem0AVRld8UK3zC9hw8QFM87WRt5zsIIt5REPRNRj7z0HJYkSgKuxz+wbJBZMG5OhcXr4q7ZcYGhIUJsb8pt+fRCWADUTajyV7rhAM8T7UIOhUfyLU734U7uTTxLXYInG1ceibydSI1vb0bfdESq4RWGQWdYmP0NWgT7VYnp0I4= 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=45.249.212.187 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 [172.19.163.252]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4bkSLL2PFcz14Lx6; Sat, 19 Jul 2025 08:32:58 +0800 (CST) Received: from dggpemf500013.china.huawei.com (unknown [7.185.36.188]) by mail.maildlp.com (Postfix) with ESMTPS id 4E1F3180B3F; Sat, 19 Jul 2025 08:37:46 +0800 (CST) Received: from [127.0.0.1] (10.174.177.71) 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; Sat, 19 Jul 2025 08:37:45 +0800 Message-ID: Date: Sat, 19 Jul 2025 08:37:44 +0800 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 01/17] ext4: add ext4_try_lock_group() to skip busy groups To: Ojaswin Mujoo CC: , , , , , , , , References: <20250714130327.1830534-1-libaokun1@huawei.com> <20250714130327.1830534-2-libaokun1@huawei.com> Content-Language: en-US From: Baokun Li In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To dggpemf500013.china.huawei.com (7.185.36.188) On 2025/7/17 18:09, Ojaswin Mujoo wrote: > On Mon, Jul 14, 2025 at 09:03:11PM +0800, Baokun Li wrote: >> When ext4 allocates blocks, we used to just go through the block groups >> one by one to find a good one. But when there are tons of block groups >> (like hundreds of thousands or even millions) and not many have free space >> (meaning they're mostly full), it takes a really long time to check them >> all, and performance gets bad. So, we added the "mb_optimize_scan" mount >> option (which is on by default now). It keeps track of some group lists, >> so when we need a free block, we can just grab a likely group from the >> right list. This saves time and makes block allocation much faster. >> >> But when multiple processes or containers are doing similar things, like >> constantly allocating 8k blocks, they all try to use the same block group >> in the same list. Even just two processes doing this can cut the IOPS in >> half. For example, one container might do 300,000 IOPS, but if you run two >> at the same time, the total is only 150,000. >> >> Since we can already look at block groups in a non-linear way, the first >> and last groups in the same list are basically the same for finding a block >> right now. Therefore, add an ext4_try_lock_group() helper function to skip >> the current group when it is locked by another process, thereby avoiding >> contention with other processes. This helps ext4 make better use of having >> multiple block groups. >> >> Also, to make sure we don't skip all the groups that have free space >> when allocating blocks, we won't try to skip busy groups anymore when >> ac_criteria is CR_ANY_FREE. >> >> Performance test data follows: >> >> Test: Running will-it-scale/fallocate2 on CPU-bound containers. >> Observation: Average fallocate operations per container per second. >> >> |CPU: Kunpeng 920 | P80 | >> |Memory: 512GB |-------------------------| >> |960GB SSD (0.5GB/s)| base | patched | >> |-------------------|-------|-----------------| >> |mb_optimize_scan=0 | 2667 | 4821 (+80.7%) | >> |mb_optimize_scan=1 | 2643 | 4784 (+81.0%) | >> >> |CPU: AMD 9654 * 2 | P96 | >> |Memory: 1536GB |-------------------------| >> |960GB SSD (1GB/s) | base | patched | >> |-------------------|-------|-----------------| >> |mb_optimize_scan=0 | 3450 | 15371 (+345%) | >> |mb_optimize_scan=1 | 3209 | 6101 (+90.0%) | >> >> Signed-off-by: Baokun Li >> Reviewed-by: Jan Kara > Hey Baokun, I reviewed some of the patches in v2 but i think that was > very last moment so I'll add the comments in this series, dont mind the > copy paste :) > > The patch itself looks good, thanks for the changes. > > Feel free to add: > > Reviewed-by: Ojaswin Mujoo Sorry for missing your review, I've snowed under with work lately. Thanks for the review! Cheers, Baokun