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Tsirkin" X-Patchwork-Id: 13720205 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 A62D2C31D97 for ; Tue, 2 Jul 2024 20:15:04 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sOjsy-0001GR-Tr; Tue, 02 Jul 2024 16:13:56 -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 1sOjst-0001BT-W1 for qemu-devel@nongnu.org; Tue, 02 Jul 2024 16:13:53 -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 1sOjsr-0007Ny-SB for qemu-devel@nongnu.org; Tue, 02 Jul 2024 16:13:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719951229; 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: in-reply-to:in-reply-to:references:references; bh=uKK/AiLdjMfeKEPpHLdhaqq0Kf5J8WlC0WD4BsUonqY=; b=B4X4LbqVczTcOtHkSjr8iudPPUc23EBFiY7h6X/c+ZogiaBhBtqMKoEGPUHVuU/ToM0wOB 6ndXbQYB1YdSJg87Ks2QAofFqe8VXjwGCxOWc2bfvEqc7PD20k4RHjNCl3SCGWs3ILBhFC btRF3iUjF+LIFM1uiZz0wSnUmYzmHCU= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-647-n3fiUGhWP7StvdVXB-8pWQ-1; Tue, 02 Jul 2024 16:13:47 -0400 X-MC-Unique: n3fiUGhWP7StvdVXB-8pWQ-1 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-4257dd7d462so19977335e9.2 for ; Tue, 02 Jul 2024 13:13:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719951225; x=1720556025; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=uKK/AiLdjMfeKEPpHLdhaqq0Kf5J8WlC0WD4BsUonqY=; b=aXJ3Fn+YU1kWtGQuNwDeGwHOJZhH06Ut+vIKiQJuOfFTmNyJ7vcak5xJR6m8ux3FxD coxhSrtlJs77WXqTeH2bq5OO5x8L6b8g2RPqP6DmH38Iiaf0ufo+kifVm2aWJZc12nye kzR0hfjDlp7R8onng9WgTyb2h/YL/R02GQRwLBYuQSky58L0+Dge9fD92sHD0VK8FQ8U q1cEGvsyUU6EjRY4EwhrrZz9ztEvpoNjmBr/rLjCahRnYR3zN+WlhJHbTlaNAL1S01T3 3KSeRKLgmpCqNlQ6VSbG9Q7W0I9wxj5YfIzpvTPj4sstxg1z+xd54rmkp6PTvgNCgJ6G XaWQ== X-Gm-Message-State: AOJu0Yx5Bqo6U+ZLnOrhf2wl54/OUQH7eXcmuRFOII7yL3rQwY8TwM8y PwAqP34oHx6ofDkuQ8vRBXoE59Rm4Iil5S1Sg6hf2BvFqqTCbb6nwjEezi6YZ3F4DP0uEydsmTA rwRZcQx0gFWwThr992aywSbpny2WUQNVPpNezEhmUrnnKGRZFZQMDdg0foDjbIkJUWPty+2knSM IDApCBlliSoOC+t1HjpDK7dyM1VVs7Rw== X-Received: by 2002:a05:600c:2d42:b0:424:a5b4:6dd3 with SMTP id 5b1f17b1804b1-4257a0763fbmr71494085e9.36.1719951225664; Tue, 02 Jul 2024 13:13:45 -0700 (PDT) X-Google-Smtp-Source: AGHT+IG2t9q1rqluDoZRLWPLfWpEITd7C0LSIRz+RPZvSqkqcCfWG97bumt7kdF+UqubgLwlEsyqRQ== X-Received: by 2002:a05:600c:2d42:b0:424:a5b4:6dd3 with SMTP id 5b1f17b1804b1-4257a0763fbmr71493835e9.36.1719951225037; Tue, 02 Jul 2024 13:13:45 -0700 (PDT) Received: from redhat.com ([2a02:14f:1f5:eadd:8c31:db01:9d01:7604]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4256af54ecasm207528015e9.12.2024.07.02.13.13.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Jul 2024 13:13:44 -0700 (PDT) Date: Tue, 2 Jul 2024 16:13:40 -0400 From: "Michael S. Tsirkin" To: qemu-devel@nongnu.org Cc: Peter Maydell , Si-Wei Liu , Joao Martins , Jason Wang Subject: [PULL v2 02/91] vhost: Perform memory section dirty scans once per iteration Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=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: Si-Wei Liu On setups with one or more virtio-net devices with vhost on, dirty tracking iteration increases cost the bigger the number amount of queues are set up e.g. on idle guests migration the following is observed with virtio-net with vhost=on: 48 queues -> 78.11% [.] vhost_dev_sync_region.isra.13 8 queues -> 40.50% [.] vhost_dev_sync_region.isra.13 1 queue -> 6.89% [.] vhost_dev_sync_region.isra.13 2 devices, 1 queue -> 18.60% [.] vhost_dev_sync_region.isra.14 With high memory rates the symptom is lack of convergence as soon as it has a vhost device with a sufficiently high number of queues, the sufficient number of vhost devices. On every migration iteration (every 100msecs) it will redundantly query the *shared log* the number of queues configured with vhost that exist in the guest. For the virtqueue data, this is necessary, but not for the memory sections which are the same. So essentially we end up scanning the dirty log too often. To fix that, select a vhost device responsible for scanning the log with regards to memory sections dirty tracking. It is selected when we enable the logger (during migration) and cleared when we disable the logger. If the vhost logger device goes away for some reason, the logger will be re-selected from the rest of vhost devices. After making mem-section logger a singleton instance, constant cost of 7%-9% (like the 1 queue report) will be seen, no matter how many queues or how many vhost devices are configured: 48 queues -> 8.71% [.] vhost_dev_sync_region.isra.13 2 devices, 8 queues -> 7.97% [.] vhost_dev_sync_region.isra.14 Co-developed-by: Joao Martins Signed-off-by: Joao Martins Signed-off-by: Si-Wei Liu Message-Id: <1710448055-11709-2-git-send-email-si-wei.liu@oracle.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Acked-by: Jason Wang --- include/hw/virtio/vhost.h | 1 + hw/virtio/vhost.c | 67 +++++++++++++++++++++++++++++++++++---- 2 files changed, 62 insertions(+), 6 deletions(-) diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h index 02477788df..d75faf46e9 100644 --- a/include/hw/virtio/vhost.h +++ b/include/hw/virtio/vhost.h @@ -129,6 +129,7 @@ struct vhost_dev { void *opaque; struct vhost_log *log; QLIST_ENTRY(vhost_dev) entry; + QLIST_ENTRY(vhost_dev) logdev_entry; QLIST_HEAD(, vhost_iommu) iommu_list; IOMMUNotifier n; const VhostDevConfigOps *config_ops; diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index a1e8b79e1a..06fc71746e 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -45,6 +45,7 @@ static struct vhost_log *vhost_log[VHOST_BACKEND_TYPE_MAX]; static struct vhost_log *vhost_log_shm[VHOST_BACKEND_TYPE_MAX]; +static QLIST_HEAD(, vhost_dev) vhost_log_devs[VHOST_BACKEND_TYPE_MAX]; /* Memslots used by backends that support private memslots (without an fd). */ static unsigned int used_memslots; @@ -149,6 +150,47 @@ bool vhost_dev_has_iommu(struct vhost_dev *dev) } } +static inline bool vhost_dev_should_log(struct vhost_dev *dev) +{ + assert(dev->vhost_ops); + assert(dev->vhost_ops->backend_type > VHOST_BACKEND_TYPE_NONE); + assert(dev->vhost_ops->backend_type < VHOST_BACKEND_TYPE_MAX); + + return dev == QLIST_FIRST(&vhost_log_devs[dev->vhost_ops->backend_type]); +} + +static inline void vhost_dev_elect_mem_logger(struct vhost_dev *hdev, bool add) +{ + VhostBackendType backend_type; + + assert(hdev->vhost_ops); + + backend_type = hdev->vhost_ops->backend_type; + assert(backend_type > VHOST_BACKEND_TYPE_NONE); + assert(backend_type < VHOST_BACKEND_TYPE_MAX); + + if (add && !QLIST_IS_INSERTED(hdev, logdev_entry)) { + if (QLIST_EMPTY(&vhost_log_devs[backend_type])) { + QLIST_INSERT_HEAD(&vhost_log_devs[backend_type], + hdev, logdev_entry); + } else { + /* + * The first vhost_device in the list is selected as the shared + * logger to scan memory sections. Put new entry next to the head + * to avoid inadvertent change to the underlying logger device. + * This is done in order to get better cache locality and to avoid + * performance churn on the hot path for log scanning. Even when + * new devices come and go quickly, it wouldn't end up changing + * the active leading logger device at all. + */ + QLIST_INSERT_AFTER(QLIST_FIRST(&vhost_log_devs[backend_type]), + hdev, logdev_entry); + } + } else if (!add && QLIST_IS_INSERTED(hdev, logdev_entry)) { + QLIST_REMOVE(hdev, logdev_entry); + } +} + static int vhost_sync_dirty_bitmap(struct vhost_dev *dev, MemoryRegionSection *section, hwaddr first, @@ -166,12 +208,14 @@ static int vhost_sync_dirty_bitmap(struct vhost_dev *dev, start_addr = MAX(first, start_addr); end_addr = MIN(last, end_addr); - for (i = 0; i < dev->mem->nregions; ++i) { - struct vhost_memory_region *reg = dev->mem->regions + i; - vhost_dev_sync_region(dev, section, start_addr, end_addr, - reg->guest_phys_addr, - range_get_last(reg->guest_phys_addr, - reg->memory_size)); + if (vhost_dev_should_log(dev)) { + for (i = 0; i < dev->mem->nregions; ++i) { + struct vhost_memory_region *reg = dev->mem->regions + i; + vhost_dev_sync_region(dev, section, start_addr, end_addr, + reg->guest_phys_addr, + range_get_last(reg->guest_phys_addr, + reg->memory_size)); + } } for (i = 0; i < dev->nvqs; ++i) { struct vhost_virtqueue *vq = dev->vqs + i; @@ -383,6 +427,7 @@ static void vhost_log_put(struct vhost_dev *dev, bool sync) g_free(log); } + vhost_dev_elect_mem_logger(dev, false); dev->log = NULL; dev->log_size = 0; } @@ -998,6 +1043,15 @@ static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log) goto err_vq; } } + + /* + * At log start we select our vhost_device logger that will scan the + * memory sections and skip for the others. This is possible because + * the log is shared amongst all vhost devices for a given type of + * backend. + */ + vhost_dev_elect_mem_logger(dev, enable_log); + return 0; err_vq: for (; i >= 0; --i) { @@ -2075,6 +2129,7 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings) VHOST_OPS_DEBUG(r, "vhost_set_log_base failed"); goto fail_log; } + vhost_dev_elect_mem_logger(hdev, true); } if (vrings) { r = vhost_dev_set_vring_enable(hdev, true);