From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (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 4F5A027450; Thu, 31 Jul 2025 02:39:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753929546; cv=none; b=qD4sPfgUIPubAfVwmrVZ2s6DhaGDzOEAJQ/Zpi6Sd2pLAiUAFYOgAswjzNw81yDJ0eukYd51RCusulrVdHWNYUYt8a89S5ceA0VEAWOq2j9O/ZYzf4PzSUwxNwpFQw7FVzv6a64MF2w3gl2H6kDIV0XInBlpviB15kO51DklDVo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753929546; c=relaxed/simple; bh=8V2vkQ4Paur/1HgNG/DwdwcZ95DNfzZ/MLpTsqpSrbY=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=c5FYljHzrHKPQ8U1HkKnT0rlRKbkZz+NvQQAz0bbpurU7CYs5x8R6Y2wn6vpa1E1G8qWwHEq71n6tHRgLvcNA5XRE3XZ0rom17bhbENO9ipl28nhYao2rCnXHLmeM+6YOMa6Bf+q28QZGtXkw/R3YBEkt+efmvvfEFvRevcq3aY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4bstZF4tRdzKHLtS; Thu, 31 Jul 2025 10:39:01 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 97BF51A1A77; Thu, 31 Jul 2025 10:39:00 +0800 (CST) Received: from [10.174.179.143] (unknown [10.174.179.143]) by APP4 (Coremail) with SMTP id gCh0CgCnIxRC14poXD46CA--.37766S3; Thu, 31 Jul 2025 10:39:00 +0800 (CST) Subject: Re: [PATCH v2 1/2] lib/sbitmap: convert shallow_depth from one word to the whole sbitmap To: yukuai@kernel.org, Jan Kara , Yu Kuai Cc: axboe@kernel.dk, akpm@linux-foundation.org, yang.yang@vivo.com, dlemoal@kernel.org, ming.lei@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, johnny.chenyi@huawei.com, Omar Sandoval , "yukuai (C)" References: <20250729031906.3615228-1-yukuai1@huaweicloud.com> <20250729031906.3615228-2-yukuai1@huaweicloud.com> <8edcdef6-8749-aa45-e7d2-ada677645d76@huaweicloud.com> <223acbc1-60d4-4687-8eea-5306aa44ae24@kernel.org> From: Yu Kuai Message-ID: Date: Thu, 31 Jul 2025 10:38:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <223acbc1-60d4-4687-8eea-5306aa44ae24@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:gCh0CgCnIxRC14poXD46CA--.37766S3 X-Coremail-Antispam: 1UD129KBjvJXoW7AF15Wr18AFyfJFW7Aw1rXrb_yoW8XF4Dpr 4UKw12k348tr1jkw1Yqa1DXF15uw13GwsxGF45Xw1xCrZ8Ja10qFyYqFy5ZF9rurW8Zayj vFWfXry7Gw1UXaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUBF14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E 2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJV W8JwACjcxG0xvEwIxGrwACjI8F5VA0II8E6IAqYI8I648v4I1lFIxGxcIEc7CjxVA2Y2ka 0xkIwI1lc7I2V7IY0VAS07AlzVAYIcxG8wCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x 0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E 7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcV C0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF 04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7 CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUd-B_UUUUU= X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ Hi, 在 2025/07/31 2:24, Yu Kuai 写道: > hi, Jan! > > 在 2025/7/30 21:03, Jan Kara 写道: >> I think having two APIs will be even more confusing than the current >> state. >> But as I wrote I think you can have API to specify shallow depth in total >> size and in sbitmap_queue_get_shallow() do: >> >> shallow_per_word = (shallow_depth << sb->shift) / sb->depth; In order to consider the last word, I think we should use __map_depth() here. >> rounding_index = shallow_depth - shallow_per_word * sb->depth; And then it's not possible to calculate this rounding index easily. How about following, although the reminder handling is not perfect. static unsigned int __map_depth_with_shallow(const struct sbitmap *sb, int index, unsigned int shallow_depth) { unsigned int word_depth = __map_depth(sb, index); unsigned int shallow_word_depth = word_depth * shallow_depth; unsigned reminder = do_div(shallow_word_depth, sb->depth); if (reminder && !(index & 0x1)) shallow_word_depth++; return shallow_word_depth; } >> >> and allow depth shallow_per_word + 1 if current index < rounding_index >> and >> exactly shallow_per_word if current index >= rounding_index. This will >> still evenly distribute shallow depth among words and I don't think the >> additional overhead of the several arithmetic operations will be visible. > Yes, you're right, I did not get your idea before. Thanks for the > explanation > and the suggestion :） Will follow this idea in the next version. > > Thanks > > . >