From patchwork Sat Dec 21 09:37:04 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 13917751 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 3E4EF1EC4DE; Sat, 21 Dec 2024 09:41:04 +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=1734774068; cv=none; b=Kzmz47wiwDutiGXD/LHJGtdsi3/ms0jmtx6tW/dYiFxssYWGqxZFgykKwpZyCRZgrCzBU29w1RyzL9A81i+JPoWXrYKxbfpBu4hZ7SeFYpWU2UeCTuFnML41xxz8yzeA1kK/LNbInlkT3sIqcdspThZjba2q0qoWpNhRzOJBR3E= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734774068; c=relaxed/simple; bh=gaX55RseTRAcsjkSIrxid4DXTHF78Q1yGOJyqdVZBFw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=nDMeXyuFDm+yhH4jFP71+2H91aatwPYpHFHmzaqT03o4tY4IrNzZ3YPFQWsOyYXmKgz16M7+IgJdK78bifjXVhy0u387QG8LFXbRiy8CQRUteaKgvvQKLy1N1jIPYa48tsuunWZuBoQ7MCCRlS/P8fBTH8yOp4V4INGOzfIM3Dk= 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 [172.19.163.235]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4YFfRF2qzQz4f3jcv; Sat, 21 Dec 2024 17:40:41 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id F29551A0568; Sat, 21 Dec 2024 17:41:00 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP4 (Coremail) with SMTP id gCh0CgBHIoYqjWZnocfeFA--.21383S5; Sat, 21 Dec 2024 17:41:00 +0800 (CST) From: Yu Kuai To: axboe@kernel.dk, akpm@linux-foundation.org, ming.lei@redhat.com, yang.yang@vivo.com, yukuai3@huawei.com, bvanassche@acm.org Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: [PATCH RFC v3 1/7] lib/sbitmap: convert shallow_depth from one word to the whole sbitmap Date: Sat, 21 Dec 2024 17:37:04 +0800 Message-Id: <20241221093710.926309-2-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20241221093710.926309-1-yukuai1@huaweicloud.com> References: <20241221093710.926309-1-yukuai1@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: gCh0CgBHIoYqjWZnocfeFA--.21383S5 X-Coremail-Antispam: 1UD129KBjvJXoW3JrW8CryDAF1rGr45tF45Awb_yoW3GFy5pF 4xt3W7KryrtF1j9rn8t3yDZF1aqws8Gr9xJF4Sqw1FkryDJan3Xr1FkFy5XFyxZFWkAFWj kFWrXry8Gw1UXFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUm014x267AKxVW5JVWrJwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jr4l82xGYIkIc2 x26xkF7I0E14v26r4j6ryUM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kIc2 xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWU JVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67 kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY 6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0x vEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVj vjDU0xZFpf9x0JU2dgAUUUUU= X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ From: Yu Kuai Both kyber and mq-deadline record internal 'async_depth' to throttle asynchronous requests, and they both calculate shallow_dpeth based on sb->shift, with the respect that sb->shift is the available tags in one word. However, sb->shift is not the availbale tags in the last word, see __map_depth: if (index == sb->map_nr - 1) return sb->depth - (index << sb->shift); What's worse, bfq just calculate shallow_depth as allowed tags for the whole sbitmap. On the one hand, callers doesn't know if the last word in bitmap will be used; on the other hand, bfq can allow only 1 request for the whole sbitmap. Fix above problems by using shallow_depth to the whole sbitmap, also change kyber and mq-deadline to follow this. Signed-off-by: Yu Kuai --- block/kyber-iosched.c | 9 ++----- block/mq-deadline.c | 16 +----------- include/linux/sbitmap.h | 6 ++--- lib/sbitmap.c | 55 +++++++++++++++++++++-------------------- 4 files changed, 34 insertions(+), 52 deletions(-) diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c index 4155594aefc6..ccfefa6a3669 100644 --- a/block/kyber-iosched.c +++ b/block/kyber-iosched.c @@ -157,10 +157,7 @@ struct kyber_queue_data { */ struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS]; - /* - * Async request percentage, converted to per-word depth for - * sbitmap_get_shallow(). - */ + /* Number of allowed async requests. */ unsigned int async_depth; struct kyber_cpu_latency __percpu *cpu_latency; @@ -454,10 +451,8 @@ static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx) { struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data; struct blk_mq_tags *tags = hctx->sched_tags; - unsigned int shift = tags->bitmap_tags.sb.shift; - - kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U; + kqd->async_depth = hctx->queue->nr_requests * KYBER_ASYNC_PERCENT / 100U; sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth); } diff --git a/block/mq-deadline.c b/block/mq-deadline.c index 5528347b5fcf..853985bd13d4 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -487,20 +487,6 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) return rq; } -/* - * 'depth' is a number in the range 1..INT_MAX representing a number of - * requests. Scale it with a factor (1 << bt->sb.shift) / q->nr_requests since - * 1..(1 << bt->sb.shift) is the range expected by sbitmap_get_shallow(). - * Values larger than q->nr_requests have the same effect as q->nr_requests. - */ -static int dd_to_word_depth(struct blk_mq_hw_ctx *hctx, unsigned int qdepth) -{ - struct sbitmap_queue *bt = &hctx->sched_tags->bitmap_tags; - const unsigned int nrr = hctx->queue->nr_requests; - - return ((qdepth << bt->sb.shift) + nrr - 1) / nrr; -} - /* * Called by __blk_mq_alloc_request(). The shallow_depth value set by this * function is used by __blk_mq_get_tag(). @@ -517,7 +503,7 @@ static void dd_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) * Throttle asynchronous requests and writes such that these requests * do not block the allocation of synchronous requests. */ - data->shallow_depth = dd_to_word_depth(data->hctx, dd->async_depth); + data->shallow_depth = dd->async_depth; } /* Called by blk_mq_update_nr_requests(). */ diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index 189140bf11fc..4adf4b364fcd 100644 --- a/include/linux/sbitmap.h +++ b/include/linux/sbitmap.h @@ -213,12 +213,12 @@ int sbitmap_get(struct sbitmap *sb); * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap, * limiting the depth used from each word. * @sb: Bitmap to allocate from. - * @shallow_depth: The maximum number of bits to allocate from a single word. + * @shallow_depth: The maximum number of bits to allocate from the bitmap. * * This rather specific operation allows for having multiple users with * different allocation limits. E.g., there can be a high-priority class that * uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow() - * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority + * with a @shallow_depth of (sb->depth >> 1). Then, the low-priority * class can only allocate half of the total bits in the bitmap, preventing it * from starving out the high-priority class. * @@ -478,7 +478,7 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags, * sbitmap_queue, limiting the depth used from each word, with preemption * already disabled. * @sbq: Bitmap queue to allocate from. - * @shallow_depth: The maximum number of bits to allocate from a single word. + * @shallow_depth: The maximum number of bits to allocate from the queue. * See sbitmap_get_shallow(). * * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after diff --git a/lib/sbitmap.c b/lib/sbitmap.c index d3412984170c..f2e90ac6b56e 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -208,8 +208,27 @@ static int sbitmap_find_bit_in_word(struct sbitmap_word *map, return nr; } +static unsigned int __map_depth_with_shallow(const struct sbitmap *sb, + int index, + unsigned int shallow_depth) +{ + unsigned int lower_bound = 0; + + if (shallow_depth >= sb->depth) + return __map_depth(sb, index); + + if (index > 0) + lower_bound += (index - 1) << sb->shift; + + if (shallow_depth <= lower_bound) + return 0; + + return min_t(unsigned int, __map_depth(sb, index), + shallow_depth - lower_bound); +} + static int sbitmap_find_bit(struct sbitmap *sb, - unsigned int depth, + unsigned int shallow_depth, unsigned int index, unsigned int alloc_hint, bool wrap) @@ -218,12 +237,12 @@ static int sbitmap_find_bit(struct sbitmap *sb, int nr = -1; for (i = 0; i < sb->map_nr; i++) { - nr = sbitmap_find_bit_in_word(&sb->map[index], - min_t(unsigned int, - __map_depth(sb, index), - depth), - alloc_hint, wrap); + unsigned int depth = __map_depth_with_shallow(sb, index, + shallow_depth); + if (depth) + nr = sbitmap_find_bit_in_word(&sb->map[index], depth, + alloc_hint, wrap); if (nr != -1) { nr += index << sb->shift; break; @@ -406,27 +425,9 @@ EXPORT_SYMBOL_GPL(sbitmap_bitmap_show); static unsigned int sbq_calc_wake_batch(struct sbitmap_queue *sbq, unsigned int depth) { - unsigned int wake_batch; - unsigned int shallow_depth; - - /* - * Each full word of the bitmap has bits_per_word bits, and there might - * be a partial word. There are depth / bits_per_word full words and - * depth % bits_per_word bits left over. In bitwise arithmetic: - * - * bits_per_word = 1 << shift - * depth / bits_per_word = depth >> shift - * depth % bits_per_word = depth & ((1 << shift) - 1) - * - * Each word can be limited to sbq->min_shallow_depth bits. - */ - shallow_depth = min(1U << sbq->sb.shift, sbq->min_shallow_depth); - depth = ((depth >> sbq->sb.shift) * shallow_depth + - min(depth & ((1U << sbq->sb.shift) - 1), shallow_depth)); - wake_batch = clamp_t(unsigned int, depth / SBQ_WAIT_QUEUES, 1, - SBQ_WAKE_BATCH); - - return wake_batch; + return clamp_t(unsigned int, + min(depth, sbq->min_shallow_depth) / SBQ_WAIT_QUEUES, + 1, SBQ_WAKE_BATCH); } int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,