From: Shahaf Shuler <shahafs@mellanox.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
Ilya Maximets <i.maximets@samsung.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
Maxime Coquelin <maxime.coquelin@redhat.com>,
Xiao Wang <xiao.w.wang@intel.com>,
"jfreimann@redhat.com" <jfreimann@redhat.com>,
Tiwei Bie <tiwei.bie@intel.com>,
Zhihong Wang <zhihong.wang@intel.com>,
Jason Wang <jasowang@redhat.com>,
"xiaolong.ye@intel.com" <xiaolong.ye@intel.com>,
"alejandro.lucero@netronome.com" <alejandro.lucero@netronome.com>,
Daniel Marcovitch <danielm@mellanox.com>
Subject: Re: [dpdk-dev] [PATCH v2] net/virtio: add platform memory ordering feature support
Date: Thu, 10 Jan 2019 20:36:45 +0000 [thread overview]
Message-ID: <DB7PR05MB4426023DA7130006F6084E1FC3840@DB7PR05MB4426.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <20190109104855-mutt-send-email-mst@kernel.org>
Wednesday, January 9, 2019 5:50 PM, Michael S. Tsirkin:
> alejandro.lucero@netronome.com; Daniel Marcovitch
> <danielm@mellanox.com>
> Subject: Re: [dpdk-dev] [PATCH v2] net/virtio: add platform memory
> ordering feature support
>
> On Wed, Jan 09, 2019 at 05:34:38PM +0300, Ilya Maximets wrote:
> > virtio_mb() is really heavy. I'd like to avoid it somehow, but I don't
> > know how to do this yet.
>
> Linux driver doesn't avoid it either.
I understand v3 was merged but still would like to continue the discuss and make sure all is clear and agreed.
Form patch [1] description it is very clear why we need the rte_smp_mb() barrier.
However I am not sure why this barrier is interoperate into rte_mb in case of vDPA. In vDPA case, both read of the user ring and write of the avail index are for local cached memory.
The only write which is to uncachable memory (device memory) is the notify itself.
As I mentioned, there is a need to have a store fence before doing the notify, but from different reasons. So vDPA use case and need Is a bit different than what presented in [1].
[1]
https://patches.dpdk.org/patch/49545/
>
> --
> MST
next prev parent reply other threads:[~2019-01-10 20:36 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20181214153817eucas1p19a41cdd791879252e1f3a5d77c427845@eucas1p1.samsung.com>
2018-12-14 15:38 ` [dpdk-dev] [PATCH] " Ilya Maximets
2018-12-14 17:00 ` Michael S. Tsirkin
2018-12-14 17:23 ` Ilya Maximets
[not found] ` <CGME20181226163717eucas1p15276eb45e35abe2c9cf3e7c1e0050823@eucas1p1.samsung.com>
2018-12-26 16:37 ` [dpdk-dev] [PATCH v2] " Ilya Maximets
2018-12-27 10:07 ` Shahaf Shuler
2019-01-09 14:34 ` Ilya Maximets
2019-01-09 15:50 ` Michael S. Tsirkin
2019-01-10 20:36 ` Shahaf Shuler [this message]
2019-01-15 6:33 ` Shahaf Shuler
2019-01-15 8:29 ` Ilya Maximets
2019-01-15 8:55 ` Shahaf Shuler
2019-01-15 10:23 ` Ilya Maximets
2019-02-12 17:50 ` Michael S. Tsirkin
[not found] ` <CGME20190109145021eucas1p1bfe194ffafaaaa5df62243c92b2ed6cd@eucas1p1.samsung.com>
2019-01-09 14:50 ` [dpdk-dev] [PATCH v3 0/3] Missing barriers and VIRTIO_F_ORDER_PLATFORM Ilya Maximets
[not found] ` <CGME20190109145027eucas1p2437215de0df4c691eb84d4e84bfc71e5@eucas1p2.samsung.com>
2019-01-09 14:50 ` [dpdk-dev] [PATCH v3 1/3] net/virtio: add missing barrier before reading the flags Ilya Maximets
2019-01-10 14:31 ` Maxime Coquelin
[not found] ` <CGME20190109145034eucas1p2183e275e316b87917b96fa184fc7d7cb@eucas1p2.samsung.com>
2019-01-09 14:50 ` [dpdk-dev] [PATCH v3 2/3] net/virtio: update memory ordering comment for vq notify Ilya Maximets
2019-01-10 8:19 ` Gavin Hu (Arm Technology China)
2019-01-10 9:18 ` Maxime Coquelin
2019-01-10 9:55 ` Ilya Maximets
2019-01-10 14:56 ` Michael S. Tsirkin
2019-01-10 14:31 ` Maxime Coquelin
[not found] ` <CGME20190109145040eucas1p2d9afc678ef94986544bde07b77373e6f@eucas1p2.samsung.com>
2019-01-09 14:50 ` [dpdk-dev] [PATCH v3 3/3] net/virtio: add platform memory ordering feature support Ilya Maximets
2019-01-10 14:31 ` Maxime Coquelin
2019-01-09 14:55 ` [dpdk-dev] [PATCH v3 0/3] Missing barriers and VIRTIO_F_ORDER_PLATFORM Michael S. Tsirkin
2019-01-09 15:24 ` Ilya Maximets
2019-01-09 16:53 ` Ferruh Yigit
2019-01-10 15:19 ` Maxime Coquelin
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