From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3C43E1170E for ; Mon, 11 Sep 2023 14:06:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B61CCC433C7; Mon, 11 Sep 2023 14:06:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1694441183; bh=mx6wC7BpBDDcFtQSn0S+OyEHLJTBU1q/E4Q/FEOJJPY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tZhZKQkqWr+emCXO4h9mtSmG8wqb3uslxX7FiX071wCQ5Ytida1XL7ZTwb0ubMci4 VQ9F+p0BYTM8buTLbp4VximYV7JzuUXUQHrKEwdUvima3V7rZiWYS13zyqutz4MnlH gCA9nwsTC9EX1Bl4h9rxgzgqVxsQHzt5M8OV514U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zhiguo Niu , Bart Van Assche , Jens Axboe , Sasha Levin Subject: [PATCH 6.5 324/739] block/mq-deadline: use correct way to throttling write requests Date: Mon, 11 Sep 2023 15:42:03 +0200 Message-ID: <20230911134700.152468033@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230911134650.921299741@linuxfoundation.org> References: <20230911134650.921299741@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhiguo Niu [ Upstream commit d47f9717e5cfd0dd8c0ba2ecfa47c38d140f1bb6 ] The original formula was inaccurate: dd->async_depth = max(1UL, 3 * q->nr_requests / 4); For write requests, when we assign a tags from sched_tags, data->shallow_depth will be passed to sbitmap_find_bit, see the following code: nr = sbitmap_find_bit_in_word(&sb->map[index], min_t (unsigned int, __map_depth(sb, index), depth), alloc_hint, wrap); The smaller of data->shallow_depth and __map_depth(sb, index) will be used as the maximum range when allocating bits. For a mmc device (one hw queue, deadline I/O scheduler): q->nr_requests = sched_tags = 128, so according to the previous calculation method, dd->async_depth = data->shallow_depth = 96, and the platform is 64bits with 8 cpus, sched_tags.bitmap_tags.sb.shift=5, sb.maps[]=32/32/32/32, 32 is smaller than 96, whether it is a read or a write I/O, tags can be allocated to the maximum range each time, which has not throttling effect. In addition, refer to the methods of bfg/kyber I/O scheduler, limit ratiois are calculated base on sched_tags.bitmap_tags.sb.shift. This patch can throttle write requests really. Fixes: 07757588e507 ("block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests") Signed-off-by: Zhiguo Niu Reviewed-by: Bart Van Assche Link: https://lore.kernel.org/r/1691061162-22898-1-git-send-email-zhiguo.niu@unisoc.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/mq-deadline.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block/mq-deadline.c b/block/mq-deadline.c index 02a916ba62ee7..f958e79277b8b 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -646,8 +646,9 @@ static void dd_depth_updated(struct blk_mq_hw_ctx *hctx) struct request_queue *q = hctx->queue; struct deadline_data *dd = q->elevator->elevator_data; struct blk_mq_tags *tags = hctx->sched_tags; + unsigned int shift = tags->bitmap_tags.sb.shift; - dd->async_depth = max(1UL, 3 * q->nr_requests / 4); + dd->async_depth = max(1U, 3 * (1U << shift) / 4); sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, dd->async_depth); } -- 2.40.1