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 DFE60CCFA05 for ; Tue, 4 Nov 2025 17:57:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vGLGi-0002cz-PL; Tue, 04 Nov 2025 12:56:33 -0500 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 1vGLFE-0001C9-1l for qemu-devel@nongnu.org; Tue, 04 Nov 2025 12:55:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vGLF9-0006oY-QT for qemu-devel@nongnu.org; Tue, 04 Nov 2025 12:54:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762278895; 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=VTY5t+mi42Og4AXvn+4mUT3pJyYT+KoDFmfS0kG2Pro=; b=gbqDMIGMjhCo0mFQ+pYmOVeVGFJEemIc/77sDL1s6Yc+el+c2H/RSpaiEu0JSOiL0jr1Tp uQTCfAye9965W8P3G0RYnx5ZVCgUdedFd3XpC2fj4U72v/mHK1VdMnCpjMAII1peQXJ0N4 Wdq1MHCm95wr6e8fRoQFWLkeNln0IR0= 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-441-Jec2Fq_dNr-kFQmDE-8CRw-1; Tue, 04 Nov 2025 12:54:52 -0500 X-MC-Unique: Jec2Fq_dNr-kFQmDE-8CRw-1 X-Mimecast-MFC-AGG-ID: Jec2Fq_dNr-kFQmDE-8CRw_1762278891 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 A249A1800378; Tue, 4 Nov 2025 17:54:51 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.45.226.47]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 5F3F91800451; Tue, 4 Nov 2025 17:54:50 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 15/27] block/io_uring: use non-vectored read/write when possible Date: Tue, 4 Nov 2025 18:54:03 +0100 Message-ID: <20251104175415.525388-16-kwolf@redhat.com> In-Reply-To: <20251104175415.525388-1-kwolf@redhat.com> References: <20251104175415.525388-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.788, 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_H3=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=ham 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 From: Stefan Hajnoczi 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 Message-ID: <20251104022933.618123-16-stefanha@redhat.com> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- block/io_uring.c | 34 ++++++++++++++++++++++++++-------- 1 file changed, 26 insertions(+), 8 deletions(-) diff --git a/block/io_uring.c b/block/io_uring.c index dd930ee57e..f1514cf024 100644 --- a/block/io_uring.c +++ b/block/io_uring.c @@ -46,17 +46,28 @@ static void luring_prep_sqe(struct io_uring_sqe *sqe, void *opaque) switch (req->type) { case QEMU_AIO_WRITE: -#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) { +#ifdef HAVE_IO_URING_PREP_WRITEV2 + io_uring_prep_writev2(sqe, fd, qiov->iov, + qiov->niov, offset, luring_flags); #else - assert(flags == 0); - io_uring_prep_writev(sqe, fd, qiov->iov, qiov->niov, offset); + /* + * FUA should only be enabled with HAVE_IO_URING_PREP_WRITEV2, see + * luring_has_fua(). + */ + assert(luring_flags == 0); + + io_uring_prep_writev(sqe, fd, qiov->iov, qiov->niov, offset); #endif + } 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); + } break; + } case QEMU_AIO_ZONE_APPEND: io_uring_prep_writev(sqe, fd, qiov->iov, qiov->niov, offset); break; @@ -65,8 +76,15 @@ 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: -- 2.51.1