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From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: linhaifeng <haifeng.lin@huawei.com>
Cc: dev@dpdk.org, Maxime Coquelin <maxime.coquelin@redhat.com>
Subject: Re: [dpdk-dev] [PATCH 0/6] vhost: add Tx zero copy support
Date: Mon, 10 Oct 2016 16:03:39 +0800	[thread overview]
Message-ID: <20161010080339.GC1597@yliu-dev.sh.intel.com> (raw)
In-Reply-To: <57FA2014.1020904@huawei.com>

On Sun, Oct 09, 2016 at 06:46:44PM +0800, linhaifeng wrote:
> 在 2016/8/23 16:10, Yuanhan Liu 写道:
> > The basic idea of Tx zero copy is, instead of copying data from the
> > desc buf, here we let the mbuf reference the desc buf addr directly.
> 
> Is there problem when push vlan to the mbuf which reference the desc buf addr directly?

Yes, you can't do that when zero copy is enabled, due to following code
piece:

    +               if (unlikely(dev->dequeue_zero_copy && (hpa = gpa_to_hpa(dev,
    +                                       desc->addr + desc_offset, cpy_len)))) {
    +                       cur->data_len = cpy_len;
==> +                       cur->data_off = 0;
    +                       cur->buf_addr = (void *)(uintptr_t)desc_addr;
    +                       cur->buf_physaddr = hpa;

The marked line basically makes the mbuf has no headroom to use.

	--yliu

> We know if guest use virtio_net(kernel) maybe skb has no headroom.

  reply	other threads:[~2016-10-10  8:02 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-23  8:10 Yuanhan Liu
2016-08-23  8:10 ` [dpdk-dev] [PATCH 1/6] vhost: simplify memory regions handling Yuanhan Liu
2016-08-23  9:17   ` Maxime Coquelin
2016-08-24  7:26   ` Xu, Qian Q
2016-08-24  7:40     ` Yuanhan Liu
2016-08-24  7:36       ` Xu, Qian Q
2016-08-23  8:10 ` [dpdk-dev] [PATCH 2/6] vhost: get guest/host physical address mappings Yuanhan Liu
2016-08-23  9:58   ` Maxime Coquelin
2016-08-23 12:32     ` Yuanhan Liu
2016-08-23 13:25       ` Maxime Coquelin
2016-08-23 13:49         ` Yuanhan Liu
2016-08-23 14:05           ` Maxime Coquelin
2016-08-23  8:10 ` [dpdk-dev] [PATCH 3/6] vhost: introduce last avail idx for Tx Yuanhan Liu
2016-08-23 12:27   ` Maxime Coquelin
2016-08-23  8:10 ` [dpdk-dev] [PATCH 4/6] vhost: add Tx zero copy Yuanhan Liu
2016-08-23 14:04   ` Maxime Coquelin
2016-08-23 14:31     ` Yuanhan Liu
2016-08-23 15:40       ` Maxime Coquelin
2016-08-23  8:10 ` [dpdk-dev] [PATCH 5/6] vhost: add a flag to enable " Yuanhan Liu
2016-09-06  9:00   ` Xu, Qian Q
2016-09-06  9:42     ` Xu, Qian Q
2016-09-06 10:02       ` Yuanhan Liu
2016-09-07  2:43         ` Xu, Qian Q
2016-09-06  9:55     ` Yuanhan Liu
2016-09-07 16:00       ` Thomas Monjalon
2016-09-08  7:21         ` Yuanhan Liu
2016-09-08  7:57           ` Thomas Monjalon
2016-08-23  8:10 ` [dpdk-dev] [PATCH 6/6] examples/vhost: add an option " Yuanhan Liu
2016-08-23  9:31   ` Thomas Monjalon
2016-08-23 12:33     ` Yuanhan Liu
2016-08-23 14:14   ` Maxime Coquelin
2016-08-23 14:45     ` Yuanhan Liu
2016-08-23 14:18 ` [dpdk-dev] [PATCH 0/6] vhost: add Tx zero copy support Maxime Coquelin
2016-08-23 14:42   ` Yuanhan Liu
2016-08-23 14:53     ` Yuanhan Liu
2016-08-23 16:41       ` Maxime Coquelin
2016-08-29  8:32 ` Xu, Qian Q
2016-08-29  8:57   ` Xu, Qian Q
2016-09-23  4:11     ` Yuanhan Liu
2016-10-09 15:20   ` Yuanhan Liu
2016-09-23  4:13 ` [dpdk-dev] [PATCH v2 0/7] vhost: add dequeue " Yuanhan Liu
2016-09-23  4:13   ` [dpdk-dev] [PATCH v2 1/7] vhost: simplify memory regions handling Yuanhan Liu
2016-09-23  4:13   ` [dpdk-dev] [PATCH v2 2/7] vhost: get guest/host physical address mappings Yuanhan Liu
2016-09-26 20:17     ` Maxime Coquelin
2016-09-23  4:13   ` [dpdk-dev] [PATCH v2 3/7] vhost: introduce last avail idx for dequeue Yuanhan Liu
2016-09-23  4:13   ` [dpdk-dev] [PATCH v2 4/7] vhost: add dequeue zero copy Yuanhan Liu
2016-09-26 20:45     ` Maxime Coquelin
2016-10-06 14:37     ` Xu, Qian Q
2016-10-09  2:03       ` Yuanhan Liu
2016-10-10 10:12         ` Xu, Qian Q
2016-10-10 10:14           ` Maxime Coquelin
2016-10-10 10:22             ` Xu, Qian Q
2016-10-10 10:40               ` Xu, Qian Q
2016-10-10 11:48               ` Maxime Coquelin
2016-09-23  4:13   ` [dpdk-dev] [PATCH v2 5/7] vhost: add a flag to enable " Yuanhan Liu
2016-09-26 20:57     ` Maxime Coquelin
2016-09-23  4:13   ` [dpdk-dev] [PATCH v2 6/7] examples/vhost: add an option " Yuanhan Liu
2016-09-26 21:05     ` Maxime Coquelin
2016-09-23  4:13   ` [dpdk-dev] [PATCH v2 7/7] net/vhost: " Yuanhan Liu
2016-09-26 21:05     ` Maxime Coquelin
2016-10-09  7:27   ` [dpdk-dev] [PATCH v3 0/7] vhost: add dequeue zero copy support Yuanhan Liu
2016-10-09  7:27     ` [dpdk-dev] [PATCH v3 1/7] vhost: simplify memory regions handling Yuanhan Liu
2016-10-09  7:27     ` [dpdk-dev] [PATCH v3 2/7] vhost: get guest/host physical address mappings Yuanhan Liu
2016-11-29  3:10       ` linhaifeng
2016-11-29 13:14       ` linhaifeng
2016-10-09  7:27     ` [dpdk-dev] [PATCH v3 3/7] vhost: introduce last avail idx for dequeue Yuanhan Liu
2016-10-09  7:27     ` [dpdk-dev] [PATCH v3 4/7] vhost: add dequeue zero copy Yuanhan Liu
2016-10-09  7:27     ` [dpdk-dev] [PATCH v3 5/7] vhost: add a flag to enable " Yuanhan Liu
2016-10-09  7:27     ` [dpdk-dev] [PATCH v3 6/7] examples/vhost: add an option " Yuanhan Liu
2016-10-09  7:28     ` [dpdk-dev] [PATCH v3 7/7] net/vhost: " Yuanhan Liu
2016-10-11 13:04     ` [dpdk-dev] [PATCH v3 0/7] vhost: add dequeue zero copy support Xu, Qian Q
2016-10-12  7:48     ` Yuanhan Liu
2016-10-09 10:46 ` [dpdk-dev] [PATCH 0/6] vhost: add Tx " linhaifeng
2016-10-10  8:03   ` Yuanhan Liu [this message]
2016-10-14  7:30     ` linhaifeng

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