From patchwork Wed May 27 10:29:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 281837 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MIME_BASE64_TEXT,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D20A3C433DF for ; Wed, 27 May 2020 10:30:48 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 9D5C6208B8 for ; Wed, 27 May 2020 10:30:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QhYV+CQG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D5C6208B8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37364 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jdtKh-0008UM-MW for qemu-devel@archiver.kernel.org; Wed, 27 May 2020 06:30:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55838) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jdtJg-0006p3-2h for qemu-devel@nongnu.org; Wed, 27 May 2020 06:29:44 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:48924 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jdtJf-00011L-71 for qemu-devel@nongnu.org; Wed, 27 May 2020 06:29:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590575382; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QzfuoH281zyXLe3OPWvxcTWK2OHxNTXKDxKKnbkGlAs=; b=QhYV+CQGS/gWM4fLwn+UWjlentJyTZETkjY8SxzBvh4rOemeJ2vgL1aDEdoBaoS0CwjBI7 DDSz7iEsCzep9Rrh64rvSGgoAI4+bfJbgt/6LCrdmETai+jqqBwpb7v/j0+iPheey+QgVG +96tG4r4AlZXLAQ34nJjoMpc693Wpic= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-91-TD_f2IsLO8iujHOjnreCOA-1; Wed, 27 May 2020 06:29:41 -0400 X-MC-Unique: TD_f2IsLO8iujHOjnreCOA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 92FB680183C; Wed, 27 May 2020 10:29:39 +0000 (UTC) Received: from localhost (ovpn-114-250.ams2.redhat.com [10.36.114.250]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0ADF46C77F; Wed, 27 May 2020 10:29:33 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH v4 1/5] virtio-pci: add virtio_pci_optimal_num_queues() helper Date: Wed, 27 May 2020 11:29:21 +0100 Message-Id: <20200527102925.128013-2-stefanha@redhat.com> In-Reply-To: <20200527102925.128013-1-stefanha@redhat.com> References: <20200527102925.128013-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=207.211.31.81; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/27 00:45:05 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 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, MIME_BASE64_TEXT=1.741, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Pankaj Gupta , Eduardo Habkost , qemu-block@nongnu.org, "Michael S. Tsirkin" , cohuck@redhat.com, Max Reitz , Stefan Hajnoczi , Paolo Bonzini , Fam Zheng , Raphael Norwitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Multi-queue devices achieve the best performance when each vCPU has a dedicated queue. This ensures that virtqueue used notifications are handled on the same vCPU that submitted virtqueue buffers. When another vCPU handles the the notification an IPI will be necessary to wake the submission vCPU and this incurs a performance overhead. Provide a helper function that virtio-pci devices will use in later patches to automatically select the optimal number of queues. Signed-off-by: Stefan Hajnoczi --- hw/virtio/virtio-pci.h | 9 +++++++++ hw/virtio/virtio-pci.c | 7 +++++++ 2 files changed, 16 insertions(+) diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h index e2eaaa9182..91096f0291 100644 --- a/hw/virtio/virtio-pci.h +++ b/hw/virtio/virtio-pci.h @@ -243,4 +243,13 @@ typedef struct VirtioPCIDeviceTypeInfo { /* Register virtio-pci type(s). @t must be static. */ void virtio_pci_types_register(const VirtioPCIDeviceTypeInfo *t); +/** + * virtio_pci_optimal_num_queues: + * @fixed_queues: number of queues that are always present + * + * Returns: The optimal number of queues for a multi-queue device, excluding + * @fixed_queues. + */ +unsigned virtio_pci_optimal_num_queues(unsigned fixed_queues); + #endif diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c index d028c17c24..0c4f0100ca 100644 --- a/hw/virtio/virtio-pci.c +++ b/hw/virtio/virtio-pci.c @@ -19,6 +19,7 @@ #include "exec/memop.h" #include "standard-headers/linux/virtio_pci.h" +#include "hw/boards.h" #include "hw/virtio/virtio.h" #include "migration/qemu-file-types.h" #include "hw/pci/pci.h" @@ -2024,6 +2025,12 @@ void virtio_pci_types_register(const VirtioPCIDeviceTypeInfo *t) g_free(base_name); } +unsigned virtio_pci_optimal_num_queues(unsigned fixed_queues) +{ + /* 1:1 vq to vcpu mapping is ideal because it avoids IPIs */ + return MIN(current_machine->smp.cpus, VIRTIO_QUEUE_MAX - fixed_queues); +} + /* virtio-pci-bus */ static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,