From: "Michael S. Tsirkin" <mst@redhat.com>
To: John Fastabend <john.fastabend@gmail.com>
Cc: jasowang@redhat.com, john.r.fastabend@intel.com,
netdev@vger.kernel.org, alexei.starovoitov@gmail.com,
daniel@iogearbox.net
Subject: Re: [net PATCH v5 6/6] virtio_net: XDP support for adjust_head
Date: Mon, 23 Jan 2017 21:22:36 +0200 [thread overview]
Message-ID: <20170123205957-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20170117222259.20280.24625.stgit@john-Precision-Tower-5810>
On Tue, Jan 17, 2017 at 02:22:59PM -0800, John Fastabend wrote:
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 62dbf4b..3b129b4 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -41,6 +41,9 @@
> #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
> #define GOOD_COPY_LEN 128
>
> +/* Amount of XDP headroom to prepend to packets for use by xdp_adjust_head */
> +#define VIRTIO_XDP_HEADROOM 256
> +
> /* RX packet size EWMA. The average packet size is used to determine the packet
> * buffer size when refilling RX rings. As the entire RX ring may be refilled
> * at once, the weight is chosen so that the EWMA will be insensitive to short-
I wonder where does this number come from? This is quite a lot and
means that using XDP_PASS will slow down any sockets on top of it.
Which in turn means people will try to remove XDP when not in use,
causing resets. E.g. build_skb (which I have a patch to switch to) uses
a much more reasonable NET_SKB_PAD.
--
MST
next prev parent reply other threads:[~2017-01-23 19:22 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-17 22:19 [net PATCH v5 0/6] virtio_net XDP fixes and adjust_header support John Fastabend
2017-01-17 22:19 ` [net PATCH v5 1/6] virtio_net: use dev_kfree_skb for small buffer XDP receive John Fastabend
2017-01-18 15:48 ` Michael S. Tsirkin
2017-01-23 21:08 ` Michael S. Tsirkin
2017-01-23 21:57 ` John Fastabend
2017-01-24 19:43 ` David Miller
2017-01-24 20:08 ` Michael S. Tsirkin
2017-01-24 20:11 ` David Miller
2017-01-24 20:54 ` Michael S. Tsirkin
2017-01-25 2:57 ` Jason Wang
2017-01-25 3:23 ` Michael S. Tsirkin
2017-01-25 4:02 ` John Fastabend
2017-01-25 5:46 ` Jason Wang
2017-01-25 14:47 ` Michael S. Tsirkin
2017-01-25 14:45 ` Michael S. Tsirkin
2017-01-17 22:20 ` [net PATCH v5 2/6] virtio_net: wrap rtnl_lock in test for calling with lock already held John Fastabend
2017-01-17 22:21 ` [net PATCH v5 3/6] virtio_net: factor out xdp handler for readability John Fastabend
2017-01-18 15:48 ` Michael S. Tsirkin
2017-01-17 22:21 ` [net PATCH v5 4/6] virtio_net: remove duplicate queue pair binding in XDP John Fastabend
2017-01-18 15:49 ` Michael S. Tsirkin
2017-01-17 22:22 ` [net PATCH v5 5/6] virtio_net: refactor freeze/restore logic into virtnet reset logic John Fastabend
2017-01-18 15:50 ` Michael S. Tsirkin
2017-01-17 22:22 ` [net PATCH v5 6/6] virtio_net: XDP support for adjust_head John Fastabend
2017-01-18 3:35 ` Jason Wang
2017-01-18 15:15 ` Michael S. Tsirkin
2017-01-19 3:05 ` Jason Wang
2017-01-19 21:11 ` Michael S. Tsirkin
2017-01-20 3:26 ` Jason Wang
2017-01-20 3:39 ` John Fastabend
2017-01-20 3:38 ` John Fastabend
2017-01-20 16:59 ` David Laight
2017-01-20 17:48 ` Michael S. Tsirkin
2017-01-22 2:51 ` Jason Wang
2017-01-22 4:14 ` John Fastabend
2017-01-23 17:02 ` Michael S. Tsirkin
2017-01-23 19:22 ` Michael S. Tsirkin [this message]
2017-01-23 20:09 ` Michael S. Tsirkin
2017-01-23 22:12 ` John Fastabend
2017-01-23 22:28 ` Michael S. Tsirkin
2017-01-18 15:48 ` [net PATCH v5 0/6] virtio_net XDP fixes and adjust_header support Michael S. Tsirkin
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