From nobody Sun Feb 8 09:10:41 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB178EB64D7 for ; Wed, 28 Jun 2023 12:48:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230373AbjF1MsI (ORCPT ); Wed, 28 Jun 2023 08:48:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230121AbjF1MrZ (ORCPT ); Wed, 28 Jun 2023 08:47:25 -0400 Received: from out-44.mta1.migadu.com (out-44.mta1.migadu.com [IPv6:2001:41d0:203:375::2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D7BF3580 for ; Wed, 28 Jun 2023 05:46:25 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1687956383; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=v+XqY897Bsd8trRe4zaYsQVNZ9l3mE6f4vuEKbcRGH4=; b=CSTLZSKNj6ys56vnYR2av9Ny99Lqz1lGsQthqeKYSIcQ6AA/1ibqgqVW9kWf815EDeArpi 9C1qTXEzPKb0JJNdsulSf4a5ulx+7FvHM42bKdtMAxak2qdoSqhvzC2EOfZVQn+aQOxbcQ CHFXZ5JpciTdAFydsQibQI+8YlT8oIk= From: chengming.zhou@linux.dev To: axboe@kernel.dk, tj@kernel.org Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, zhouchengming@bytedance.com, ming.lei@redhat.com, hch@lst.de Subject: [PATCH v3 3/3] blk-mq: fix start_time_ns and alloc_time_ns for pre-allocated rq Date: Wed, 28 Jun 2023 20:45:46 +0800 Message-Id: <20230628124546.1056698-4-chengming.zhou@linux.dev> In-Reply-To: <20230628124546.1056698-1-chengming.zhou@linux.dev> References: <20230628124546.1056698-1-chengming.zhou@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Chengming Zhou The iocost rely on rq start_time_ns and alloc_time_ns to tell saturation state of the block device. Most of the time request is allocated after rq_qos_throttle() and its alloc_time_ns or start_time_ns won't be affected. But for plug batched allocation introduced by the commit 47c122e35d7e ("block: pre-allocate requests if plug is started and is a batch"), we can rq_qos_throttle() after the allocation of the request. This is what the blk_mq_get_cached_request() does. In this case, the cached request alloc_time_ns or start_time_ns is much ahead if blocked in any qos ->throttle(). This patch fix it by setting alloc_time_ns and start_time_ns to now when the pre-allocated rq is actually used. And we skip setting the alloc_time_ns and start_time_ns during pre-allocation, so just pass 0 in __blk_mq_alloc_requests_batch(). Signed-off-by: Chengming Zhou --- block/blk-mq.c | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 8b981d0a868e..55a2e600f943 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -337,6 +337,24 @@ void blk_rq_init(struct request_queue *q, struct reque= st *rq) } EXPORT_SYMBOL(blk_rq_init); =20 +/* Set rq alloc and start time when pre-allocated rq is actually used */ +static inline void blk_mq_rq_time_init(struct request_queue *q, struct req= uest *rq) +{ + if (blk_mq_need_time_stamp(rq->rq_flags)) { + u64 now =3D ktime_get_ns(); + +#ifdef CONFIG_BLK_RQ_ALLOC_TIME + /* + * alloc time is only used by iocost for now, + * only possible when blk_mq_need_time_stamp(). + */ + if (blk_queue_rq_alloc_time(q)) + rq->alloc_time_ns =3D now; +#endif + rq->start_time_ns =3D now; + } +} + static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data, struct blk_mq_tags *tags, unsigned int tag, u64 alloc_time_ns, u64 start_time_ns) @@ -395,23 +413,18 @@ static struct request *blk_mq_rq_ctx_init(struct blk_= mq_alloc_data *data, } =20 static inline struct request * -__blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data, - u64 alloc_time_ns) +__blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data) { unsigned int tag, tag_offset; struct blk_mq_tags *tags; struct request *rq; unsigned long tag_mask; int i, nr =3D 0; - u64 start_time_ns =3D 0; =20 tag_mask =3D blk_mq_get_tags(data, data->nr_tags, &tag_offset); if (unlikely(!tag_mask)) return NULL; =20 - if (blk_mq_need_time_stamp(data->rq_flags)) - start_time_ns =3D ktime_get_ns(); - tags =3D blk_mq_tags_from_data(data); for (i =3D 0; tag_mask; i++) { if (!(tag_mask & (1UL << i))) @@ -419,7 +432,7 @@ __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data = *data, tag =3D tag_offset + i; prefetch(tags->static_rqs[tag]); tag_mask &=3D ~(1UL << i); - rq =3D blk_mq_rq_ctx_init(data, tags, tag, alloc_time_ns, start_time_ns); + rq =3D blk_mq_rq_ctx_init(data, tags, tag, 0, 0); rq_list_add(data->cached_rq, rq); nr++; } @@ -490,9 +503,11 @@ static struct request *__blk_mq_alloc_requests(struct = blk_mq_alloc_data *data) * Try batched alloc if we want more than 1 tag. */ if (data->nr_tags > 1) { - rq =3D __blk_mq_alloc_requests_batch(data, alloc_time_ns); - if (rq) + rq =3D __blk_mq_alloc_requests_batch(data); + if (rq) { + blk_mq_rq_time_init(q, rq); return rq; + } data->nr_tags =3D 1; } =20 @@ -575,6 +590,7 @@ static struct request *blk_mq_alloc_cached_request(stru= ct request_queue *q, return NULL; =20 plug->cached_rq =3D rq_list_next(rq); + blk_mq_rq_time_init(q, rq); } =20 rq->cmd_flags =3D opf; @@ -2896,6 +2912,7 @@ static inline struct request *blk_mq_get_cached_reque= st(struct request_queue *q, plug->cached_rq =3D rq_list_next(rq); rq_qos_throttle(q, *bio); =20 + blk_mq_rq_time_init(q, rq); rq->cmd_flags =3D (*bio)->bi_opf; INIT_LIST_HEAD(&rq->queuelist); return rq; --=20 2.39.2