From: Tiwei Bie <tiwei.bie@intel.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: dev@dpdk.org, yliu@fridaylinux.org, jfreiman@redhat.com,
mst@redhat.com, vkaplans@redhat.com, jasowang@redhat.com
Subject: Re: [dpdk-dev] [PATCH 03/21] vhost: protect virtio_net device struct
Date: Tue, 5 Sep 2017 12:45:17 +0800 [thread overview]
Message-ID: <20170905044516.GC31895@debian-ZGViaWFuCg> (raw)
In-Reply-To: <20170831095023.21037-4-maxime.coquelin@redhat.com>
On Thu, Aug 31, 2017 at 11:50:05AM +0200, Maxime Coquelin wrote:
> virtio_net device might be accessed while being reallocated
> in case of NUMA awareness. This case might be theoretical,
> but it will be needed anyway to protect vrings pages against
> invalidation.
>
> The virtio_net devs are now protected with a readers/writers
> lock, so that before reallocating the device, it is ensured
> that it is not being referenced by the processing threads.
>
[...]
>
> +struct virtio_net *
> +get_device(int vid)
> +{
> + struct virtio_net *dev;
> +
> + rte_rwlock_read_lock(&vhost_devices[vid].lock);
> +
> + dev = __get_device(vid);
> + if (unlikely(!dev))
> + rte_rwlock_read_unlock(&vhost_devices[vid].lock);
> +
> + return dev;
> +}
> +
> +void
> +put_device(int vid)
> +{
> + rte_rwlock_read_unlock(&vhost_devices[vid].lock);
> +}
> +
This patch introduced a per-device rwlock which needs to be acquired
unconditionally in the data path. So for each vhost device, the IO
threads of different queues will need to acquire/release this lock
during each enqueue and dequeue operation, which will cause cache
contention when multiple queues are enabled and handled by different
cores. With this patch alone, I saw ~7% performance drop when enabling
6 queues to do 64bytes iofwd loopback test. Is there any way to avoid
introducing this lock to the data path?
Best regards,
Tiwei Bie
next prev parent reply other threads:[~2017-09-05 4:44 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-31 9:50 [dpdk-dev] [PATCH 00/21] Vhost-user: Implement device IOTLB support Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 01/21] Revert "vhost: workaround MQ fails to startup" Maxime Coquelin
2017-09-07 11:54 ` Yuanhan Liu
2017-09-07 12:59 ` Maxime Coquelin
2017-09-24 10:41 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 02/21] vhost: make error handling consistent in rx path Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 03/21] vhost: protect virtio_net device struct Maxime Coquelin
2017-09-05 4:45 ` Tiwei Bie [this message]
2017-09-05 9:24 ` Maxime Coquelin
2017-09-05 10:07 ` Tiwei Bie
2017-09-05 11:00 ` Maxime Coquelin
2017-09-06 1:15 ` Tiwei Bie
2017-09-06 2:59 ` Stephen Hemminger
2017-09-06 7:50 ` Maxime Coquelin
2017-09-06 7:15 ` Maxime Coquelin
2017-09-06 7:30 ` Tiwei Bie
2017-09-06 20:02 ` Maxime Coquelin
2017-09-07 5:08 ` Tiwei Bie
2017-09-07 13:44 ` Yuanhan Liu
2017-09-07 14:01 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 04/21] vhost: prepare send_vhost_message() to slave requests Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 05/21] vhost: add support to slave requests channel Maxime Coquelin
2017-09-05 4:19 ` Tiwei Bie
2017-09-05 8:18 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 06/21] vhost: declare missing IOMMU-related definitions for old kernels Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 07/21] vhost: add iotlb helper functions Maxime Coquelin
2017-09-05 6:02 ` Tiwei Bie
2017-09-05 15:16 ` Maxime Coquelin
2017-09-08 8:08 ` Yuanhan Liu
2017-09-08 8:24 ` Maxime Coquelin
2017-09-08 8:36 ` Yuanhan Liu
2017-09-08 8:50 ` Maxime Coquelin
2017-09-08 9:21 ` Yuanhan Liu
2017-09-08 9:28 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 08/21] vhost: iotlb: add pending miss request list and helpers Maxime Coquelin
2017-09-05 7:11 ` Tiwei Bie
2017-09-05 15:18 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 09/21] vhost-user: add support to IOTLB miss slave requests Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 10/21] vhost: initialize vrings IOTLB caches Maxime Coquelin
2017-09-04 13:57 ` Remy Horton
2017-09-04 15:45 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 11/21] vhost-user: handle IOTLB update and invalidate requests Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 12/21] vhost: introduce guest IOVA to backend VA helper Maxime Coquelin
2017-09-05 4:14 ` Tiwei Bie
2017-09-05 7:05 ` Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 13/21] vhost: use the guest IOVA to host " Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 14/21] vhost: enable rings at the right time Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 15/21] vhost: don't dereference invalid dev pointer after its reallocation Maxime Coquelin
2017-09-04 13:58 ` Remy Horton
2017-08-31 9:50 ` [dpdk-dev] [PATCH 16/21] vhost: postpone rings addresses translation Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 17/21] vhost-user: translate ring addresses when IOMMU enabled Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 18/21] vhost-user: iommu: postpone device creation until ring are mapped Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 19/21] vhost: iommu: Invalidate vring in case of matching IOTLB invalidate Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 20/21] vhost: enable IOMMU support Maxime Coquelin
2017-08-31 9:50 ` [dpdk-dev] [PATCH 21/21] vhost: iotlb: reduce iotlb read lock usage Maxime Coquelin
2017-09-11 4:18 ` Yuanhan Liu
2017-09-11 7:34 ` Maxime Coquelin
2017-09-11 9:39 ` Yuanhan Liu
2017-09-04 13:58 ` [dpdk-dev] [PATCH 00/21] Vhost-user: Implement device IOTLB support Remy Horton
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