From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 1206B4269E; Tue, 3 Oct 2023 14:49:38 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id A09A14026C; Tue, 3 Oct 2023 14:49:37 +0200 (CEST) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by mails.dpdk.org (Postfix) with ESMTP id 368A44026B for ; Tue, 3 Oct 2023 14:49:36 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696337375; 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=Irds6B0dKZpCTGHIzU7Og3YqwmgTf7Y4pxHqpPONMbE=; b=bWXOdhau36yCEWgkI/x4WbORbElKnqftCgPi4ueUtiBBgmOCCALRuDA/g6+myuLh3j2sr/ KCDF0x77+KXFQO3X5N/6y7cicJsbrwKv7t87ulLlMCbH6dLrJUYz2e1j0n19HKt3AIAf9X N7PrwZeYpXb9RZC3/aGiR+qcwYkNPvo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-564-kssSr9uIMRWPBOWM84b7yw-1; Tue, 03 Oct 2023 08:49:32 -0400 X-MC-Unique: kssSr9uIMRWPBOWM84b7yw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 66902101AA6F; Tue, 3 Oct 2023 12:49:32 +0000 (UTC) Received: from [10.39.208.36] (unknown [10.39.208.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5FD3240C6EA8; Tue, 3 Oct 2023 12:49:31 +0000 (UTC) Message-ID: Date: Tue, 3 Oct 2023 14:49:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v3] vhost: add IRQ suppression To: Eelco Chaudron Cc: dev@dpdk.org, david.marchand@redhat.com, chenbo.xia@outlook.com References: <20230929103809.765417-1-maxime.coquelin@redhat.com> From: Maxime Coquelin In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi Eelco, On 10/3/23 14:36, Eelco Chaudron wrote: > > > On 29 Sep 2023, at 12:38, Maxime Coquelin wrote: > >> Guest notifications offloading, which has been introduced >> in v23.07, aims at offloading syscalls out of the datapath. >> >> This patch optimizes the offloading by not offloading the >> guest notification for a given virtqueue if one is already >> being offloaded by the application. >> >> With a single VDUSE device, we can already see few >> notifications being suppressed when doing throughput >> testing with Iperf3. We can expect to see much more being >> suppressed when the offloading thread is under pressure. >> >> Signed-off-by: Maxime Coquelin > > Thanks for adding this Maxime. I did some tests with OVS and my old determinism patchset, and it works perfectly. > > I have two small nits, but this change looks good to me. > > Acked-by: Eelco Chaudron > >> --- >> >> v3: s/0/false/ (David) >> >> lib/vhost/vhost.c | 4 ++++ >> lib/vhost/vhost.h | 27 +++++++++++++++++++++------ >> 2 files changed, 25 insertions(+), 6 deletions(-) >> >> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c >> index c03bb9c6eb..7fde412ef3 100644 >> --- a/lib/vhost/vhost.c >> +++ b/lib/vhost/vhost.c >> @@ -49,6 +49,8 @@ static const struct vhost_vq_stats_name_off vhost_vq_stat_strings[] = { >> stats.guest_notifications_offloaded)}, >> {"guest_notifications_error", offsetof(struct vhost_virtqueue, >> stats.guest_notifications_error)}, >> + {"guest_notifications_suppressed", offsetof(struct vhost_virtqueue, >> + stats.guest_notifications_suppressed)}, >> {"iotlb_hits", offsetof(struct vhost_virtqueue, stats.iotlb_hits)}, >> {"iotlb_misses", offsetof(struct vhost_virtqueue, stats.iotlb_misses)}, >> {"inflight_submitted", offsetof(struct vhost_virtqueue, stats.inflight_submitted)}, >> @@ -1517,6 +1519,8 @@ rte_vhost_notify_guest(int vid, uint16_t queue_id) >> >> rte_rwlock_read_lock(&vq->access_lock); >> >> + __atomic_store_n(&vq->irq_pending, false, __ATOMIC_RELEASE); >> + >> if (dev->backend_ops->inject_irq(dev, vq)) { >> if (dev->flags & VIRTIO_DEV_STATS_ENABLED) >> __atomic_fetch_add(&vq->stats.guest_notifications_error, >> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h >> index 9723429b1c..5fc9035a1f 100644 >> --- a/lib/vhost/vhost.h >> +++ b/lib/vhost/vhost.h >> @@ -156,6 +156,7 @@ struct virtqueue_stats { >> uint64_t iotlb_misses; >> uint64_t inflight_submitted; >> uint64_t inflight_completed; >> + uint64_t guest_notifications_suppressed; >> /* Counters below are atomic, and should be incremented as such. */ >> uint64_t guest_notifications; >> uint64_t guest_notifications_offloaded; >> @@ -346,6 +347,8 @@ struct vhost_virtqueue { >> >> struct vhost_vring_addr ring_addrs; >> struct virtqueue_stats stats; >> + >> + bool irq_pending; > > nit: Other elements in this structure have the names aligned, not sure if this should be done for this item also. Ha yes, you're right. I'll fix it while applying. > >> } __rte_cache_aligned; >> >> /* Virtio device status as per Virtio specification */ >> @@ -908,12 +911,24 @@ vhost_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old) >> static __rte_always_inline void >> vhost_vring_inject_irq(struct virtio_net *dev, struct vhost_virtqueue *vq) >> { >> - if (dev->notify_ops->guest_notify && >> - dev->notify_ops->guest_notify(dev->vid, vq->index)) { >> - if (dev->flags & VIRTIO_DEV_STATS_ENABLED) >> - __atomic_fetch_add(&vq->stats.guest_notifications_offloaded, >> - 1, __ATOMIC_RELAXED); >> - return; >> + bool expected = false; >> + >> + if (dev->notify_ops->guest_notify) { >> + if (__atomic_compare_exchange_n(&vq->irq_pending, &expected, true, 0, >> + __ATOMIC_RELEASE, __ATOMIC_RELAXED)) { >> + if (dev->notify_ops->guest_notify(dev->vid, vq->index)) { >> + if (dev->flags & VIRTIO_DEV_STATS_ENABLED) >> + __atomic_fetch_add(&vq->stats.guest_notifications_offloaded, >> + 1, __ATOMIC_RELAXED); >> + return; >> + } >> + >> + /* Offloading failed, fallback to direct IRQ injection */ > > nit: Some comments end with a dot and some do not, not sure what is the preference in DPDK. I'm not sure either! I'm personally fine either way. >> + __atomic_store_n(&vq->irq_pending, false, __ATOMIC_RELEASE); >> + } else { >> + vq->stats.guest_notifications_suppressed++; >> + return; >> + } >> } >> >> if (dev->backend_ops->inject_irq(dev, vq)) { >> -- >> 2.41.0 > Thanks, Maxime