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 C827DC87FCA for ; Thu, 24 Jul 2025 20:48:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uf2r3-0008CG-8X; Thu, 24 Jul 2025 16:47:53 -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 1uf2qa-0006vn-Bo for qemu-devel@nongnu.org; Thu, 24 Jul 2025 16:47:27 -0400 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 1uf2qX-0007W1-F1 for qemu-devel@nongnu.org; Thu, 24 Jul 2025 16:47:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753390036; 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=yw5wu0Bvtn1lGx974paDUSobpem7+N41X/8z4DQO0zY=; b=hlelHWjR4MqBx82LFrhMPT6m0Iw2dnfOC+vfLDQO9XUMobgfSlXs3PgJY32YftevNv0EU6 f2Thd/8koaqKRG4CIt/eBK01E4ohMvDWrMzNGEdws8ko7rXheB4GeB7QsyDMYmOa9Cbx7f d7wapr+qNmdcaxyoifJktXS4xWxOmSo= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-507-zpkpmTvyPo6-XBMwd0zDPQ-1; Thu, 24 Jul 2025 16:47:12 -0400 X-MC-Unique: zpkpmTvyPo6-XBMwd0zDPQ-1 X-Mimecast-MFC-AGG-ID: zpkpmTvyPo6-XBMwd0zDPQ_1753390031 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5B9191955BC5; Thu, 24 Jul 2025 20:47:10 +0000 (UTC) Received: from localhost (unknown [10.2.16.247]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 624451800298; Thu, 24 Jul 2025 20:47:09 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , Brian Song , qemu-block@nongnu.org, Bernd Schubert , Kevin Wolf , h0lyalg0rithm@git.sr.ht, Fam Zheng Subject: [RFC 2/3] aio-posix: enable IORING_SETUP_SINGLE_ISSUER Date: Thu, 24 Jul 2025 16:47:01 -0400 Message-ID: <20250724204702.576637-3-stefanha@redhat.com> In-Reply-To: <20250724204702.576637-1-stefanha@redhat.com> References: <20250724204702.576637-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.45, 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_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 IORING_SETUP_SINGLE_ISSUER enables optimizations in the host Linux kernel's io_uring code when the io_uring context is only used from a single thread. This is true is QEMU because io_uring SQEs are submitted from the same thread that processes the CQEs. Signed-off-by: Stefan Hajnoczi --- util/fdmon-io_uring.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/util/fdmon-io_uring.c b/util/fdmon-io_uring.c index 28b93c8ab9..4798439097 100644 --- a/util/fdmon-io_uring.c +++ b/util/fdmon-io_uring.c @@ -456,13 +456,30 @@ static const FDMonOps fdmon_io_uring_ops = { .add_sqe = fdmon_io_uring_add_sqe, }; +static inline bool is_creating_iothread(void) +{ + return qemu_get_thread_id() != getpid(); +} + void fdmon_io_uring_setup(AioContext *ctx, Error **errp) { int ret; + /* TODO only enable these flags if they are available in the host's kernel headers */ + unsigned flags = 0; ctx->io_uring_fd_tag = NULL; - ret = io_uring_queue_init(FDMON_IO_URING_ENTRIES, &ctx->fdmon_io_uring, 0); + /* + * The main thread's AioContexts are created from the main loop thread but + * may be accessed from multiple threads (e.g. vCPUs or the migration + * thread). IOThread AioContexts are only accessed from the IOThread + * itself. + */ + if (is_creating_iothread()) { + flags = IORING_SETUP_SINGLE_ISSUER; + } + + ret = io_uring_queue_init(FDMON_IO_URING_ENTRIES, &ctx->fdmon_io_uring, flags); if (ret != 0) { error_setg_errno(errp, -ret, "Failed to initialize io_uring"); return; -- 2.50.1