From nobody Sat Feb 7 18:46:41 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 BD743EB64DD for ; Thu, 29 Jun 2023 11:07:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232210AbjF2LHX (ORCPT ); Thu, 29 Jun 2023 07:07:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232138AbjF2LHQ (ORCPT ); Thu, 29 Jun 2023 07:07:16 -0400 Received: from out-55.mta1.migadu.com (out-55.mta1.migadu.com [IPv6:2001:41d0:203:375::37]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94B16E72 for ; Thu, 29 Jun 2023 04:07:15 -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=1688036833; 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=dNin81+NgdWvZKUgysygT1wpEuRFau3v3obyeOkX5fM=; b=wwqEmJdrPmGhPaPCNNeah4+ETGQTleAhQTC7xostmyZuZdJychdvBYIDsi+H4x6MrfHW8p c6P2ePqkoYs95JZypBggJd7pyt64ZMEfrqpnao0izFegeXWFKgAL8UwFUZRoOWGW+V21oL hto1QBQcoDWwYWAKXB5SN1k+aLYpCkk= From: chengming.zhou@linux.dev To: axboe@kernel.dk, ming.lei@redhat.com, hch@lst.de, tj@kernel.org Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Chengming Zhou Subject: [PATCH v2 1/4] blk-mq: use percpu csd to remote complete instead of per-rq csd Date: Thu, 29 Jun 2023 19:03:56 +0800 Message-Id: <20230629110359.1111832-2-chengming.zhou@linux.dev> In-Reply-To: <20230629110359.1111832-1-chengming.zhou@linux.dev> References: <20230629110359.1111832-1-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 If request need to be completed remotely, we insert it into percpu llist, and smp_call_function_single_async() if llist is empty previously. We don't need to use per-rq csd, percpu csd is enough. And the size of struct request is decreased by 24 bytes. This way is cleaner, and looks correct, given block softirq is guaranteed t= o be scheduled to consume the list if one new request is added to this percpu li= st, either smp_call_function_single_async() returns -EBUSY or 0. Signed-off-by: Chengming Zhou Reviewed-by: Ming Lei --- v2: - Change to use call_single_data_t, which avoid to use 2 cache lines for 1 csd, as suggested by Ming Lei. - Improve the commit log, the explanation is copied from Ming Lei. --- block/blk-mq.c | 12 ++++++++---- include/linux/blk-mq.h | 5 +---- 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index decb6ab2d508..e52200edd2b1 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -43,6 +43,7 @@ #include "blk-ioprio.h" =20 static DEFINE_PER_CPU(struct llist_head, blk_cpu_done); +static DEFINE_PER_CPU(call_single_data_t, blk_cpu_csd); =20 static void blk_mq_insert_request(struct request *rq, blk_insert_t flags); static void blk_mq_request_bypass_insert(struct request *rq, @@ -1156,13 +1157,13 @@ static void blk_mq_complete_send_ipi(struct request= *rq) { struct llist_head *list; unsigned int cpu; + call_single_data_t *csd; =20 cpu =3D rq->mq_ctx->cpu; list =3D &per_cpu(blk_cpu_done, cpu); - if (llist_add(&rq->ipi_list, list)) { - INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq); - smp_call_function_single_async(cpu, &rq->csd); - } + csd =3D &per_cpu(blk_cpu_csd, cpu); + if (llist_add(&rq->ipi_list, list)) + smp_call_function_single_async(cpu, csd); } =20 static void blk_mq_raise_softirq(struct request *rq) @@ -4796,6 +4797,9 @@ static int __init blk_mq_init(void) =20 for_each_possible_cpu(i) init_llist_head(&per_cpu(blk_cpu_done, i)); + for_each_possible_cpu(i) + INIT_CSD(&per_cpu(blk_cpu_csd, i), + __blk_mq_complete_request_remote, NULL); open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); =20 cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD, diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index f401067ac03a..070551197c0e 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -182,10 +182,7 @@ struct request { rq_end_io_fn *saved_end_io; } flush; =20 - union { - struct __call_single_data csd; - u64 fifo_time; - }; + u64 fifo_time; =20 /* * completion callback. --=20 2.39.2