From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 49686CA0FED for ; Wed, 10 Sep 2025 18:11:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uwPGC-0006c6-S7; Wed, 10 Sep 2025 14:09:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uwPDp-0004mi-Fm for qemu-devel@nongnu.org; Wed, 10 Sep 2025 14:07:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uwPDm-00057Z-Tc for qemu-devel@nongnu.org; Wed, 10 Sep 2025 14:07:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757527625; 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=m7ShvVxcohLryooGwoHjde/Zqt4sTaKcWehk8sb96Oo=; b=Ak05ZdTSwk/0fE7kHctvD7J64zSqOD5h64ppvy4JkZYy8vyBjfLLalpQ03Qa8AMKXmhZoj 0PacsUhFDeh7n0kSo1HFh4pCNAThKQwcAF7No4sRdhqBwyUEbCYhTJZ0JWhxpwyeoDJ6dG QkXQUqL81mUyrMJLyuCESpU4X9ZumbM= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-122-iNFkpZrvP42qcidO9zzaaw-1; Wed, 10 Sep 2025 14:07:02 -0400 X-MC-Unique: iNFkpZrvP42qcidO9zzaaw-1 X-Mimecast-MFC-AGG-ID: iNFkpZrvP42qcidO9zzaaw_1757527620 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B5AC9180047F; Wed, 10 Sep 2025 18:07:00 +0000 (UTC) Received: from localhost (unknown [10.2.17.66]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 325B91956095; Wed, 10 Sep 2025 18:06:59 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Aarushi Mehta , Fam Zheng , Stefano Garzarella , Hanna Czenczek , eblake@redhat.com, Stefan Hajnoczi , Kevin Wolf , qemu-block@nongnu.org, hibriansong@gmail.com, Stefan Weil , Paolo Bonzini Subject: [PATCH v4 12/12] block/io_uring: use non-vectored read/write when possible Date: Wed, 10 Sep 2025 13:57:03 -0400 Message-ID: <20250910175703.374499-13-stefanha@redhat.com> In-Reply-To: <20250910175703.374499-1-stefanha@redhat.com> References: <20250910175703.374499-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org The io_uring_prep_readv2/writev2() man pages recommend using the non-vectored read/write operations when possible for performance reasons. I didn't measure a significant difference but it doesn't hurt to have this optimization in place. Suggested-by: Eric Blake Signed-off-by: Stefan Hajnoczi --- block/io_uring.c | 29 ++++++++++++++++++++++++----- 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/block/io_uring.c b/block/io_uring.c index dd930ee57e..bbefbddcc0 100644 --- a/block/io_uring.c +++ b/block/io_uring.c @@ -49,12 +49,24 @@ static void luring_prep_sqe(struct io_uring_sqe *sqe, void *opaque) #ifdef HAVE_IO_URING_PREP_WRITEV2 { int luring_flags = (flags & BDRV_REQ_FUA) ? RWF_DSYNC : 0; - io_uring_prep_writev2(sqe, fd, qiov->iov, - qiov->niov, offset, luring_flags); + if (luring_flags != 0 || qiov->niov > 1) { + io_uring_prep_writev2(sqe, fd, qiov->iov, + qiov->niov, offset, luring_flags); + } else { + /* The man page says non-vectored is faster than vectored */ + struct iovec *iov = qiov->iov; + io_uring_prep_write(sqe, fd, iov->iov_base, iov->iov_len, offset); + } } #else assert(flags == 0); - io_uring_prep_writev(sqe, fd, qiov->iov, qiov->niov, offset); + if (qiov->niov > 1) { + io_uring_prep_writev(sqe, fd, qiov->iov, qiov->niov, offset); + } else { + /* The man page says non-vectored is faster than vectored */ + struct iovec *iov = qiov->iov; + io_uring_prep_write(sqe, fd, iov->iov_base, iov->iov_len, offset); + } #endif break; case QEMU_AIO_ZONE_APPEND: @@ -65,8 +77,15 @@ static void luring_prep_sqe(struct io_uring_sqe *sqe, void *opaque) if (req->resubmit_qiov.iov != NULL) { qiov = &req->resubmit_qiov; } - io_uring_prep_readv(sqe, fd, qiov->iov, qiov->niov, - offset + req->total_read); + if (qiov->niov > 1) { + io_uring_prep_readv(sqe, fd, qiov->iov, qiov->niov, + offset + req->total_read); + } else { + /* The man page says non-vectored is faster than vectored */ + struct iovec *iov = qiov->iov; + io_uring_prep_read(sqe, fd, iov->iov_base, iov->iov_len, + offset + req->total_read); + } break; } case QEMU_AIO_FLUSH: -- 2.51.0