| Message ID | 158824568241.2172139.9308631605958332864.stgit@firesoul |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [net-next,v2,01/33] xdp: add frame size to xdp_buff | expand |
> -----Original Message----- > From: Jesper Dangaard Brouer <brouer@redhat.com> > Sent: Thursday, April 30, 2020 7:21 AM > To: sameehj@amazon.com > Cc: Wei Liu <wei.liu@kernel.org>; KY Srinivasan <kys@microsoft.com>; > Haiyang Zhang <haiyangz@microsoft.com>; Stephen Hemminger > <sthemmin@microsoft.com>; Jesper Dangaard Brouer > <brouer@redhat.com>; netdev@vger.kernel.org; bpf@vger.kernel.org; > zorik@amazon.com; akiyano@amazon.com; gtzalik@amazon.com; Toke > Høiland-Jørgensen <toke@redhat.com>; Daniel Borkmann > <borkmann@iogearbox.net>; Alexei Starovoitov > <alexei.starovoitov@gmail.com>; John Fastabend > <john.fastabend@gmail.com>; Alexander Duyck > <alexander.duyck@gmail.com>; Jeff Kirsher <jeffrey.t.kirsher@intel.com>; > David Ahern <dsahern@gmail.com>; Willem de Bruijn > <willemdebruijn.kernel@gmail.com>; Ilias Apalodimas > <ilias.apalodimas@linaro.org>; Lorenzo Bianconi <lorenzo@kernel.org>; > Saeed Mahameed <saeedm@mellanox.com>; > steffen.klassert@secunet.com > Subject: [PATCH net-next v2 12/33] hv_netvsc: add XDP frame size to driver > > The hyperv NIC drivers XDP implementation is rather disappointing as it will > be a slowdown to enable XDP on this driver, given it will allocate a new page > for each packet and copy over the payload, before invoking the XDP BPF- > prog. This needs correction. As I said previously -- This statement is not accurate -- The data path of netvsc driver does memory allocation and copy even without XDP, so it's not "a slowdown to enable XDP". Thanks, - Haiyang
On Thu, 30 Apr 2020 14:20:20 +0000 Haiyang Zhang <haiyangz@microsoft.com> wrote: > > -----Original Message----- > > From: Jesper Dangaard Brouer <brouer@redhat.com> > > > > The hyperv NIC drivers XDP implementation is rather disappointing as it will > > be a slowdown to enable XDP on this driver, given it will allocate a new page > > for each packet and copy over the payload, before invoking the XDP BPF- > > prog. > > This needs correction. As I said previously -- > This statement is not accurate -- The data path of netvsc driver does memory > allocation and copy even without XDP, so it's not "a slowdown to enable XDP". Okay, I have changed the paragraph text to: The hyperv NIC driver does memory allocation and copy even without XDP. In XDP mode it will allocate a new page for each packet and copy over the payload, before invoking the XDP BPF-prog.
diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c index b86611041db6..1e0c024b0a93 100644 --- a/drivers/net/hyperv/netvsc_bpf.c +++ b/drivers/net/hyperv/netvsc_bpf.c @@ -49,6 +49,7 @@ u32 netvsc_run_xdp(struct net_device *ndev, struct netvsc_channel *nvchan, xdp_set_data_meta_invalid(xdp); xdp->data_end = xdp->data + len; xdp->rxq = &nvchan->xdp_rxq; + xdp->frame_sz = PAGE_SIZE; xdp->handle = 0; memcpy(xdp->data, data, len); diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c index d8e86bdbfba1..651344fea0a5 100644 --- a/drivers/net/hyperv/netvsc_drv.c +++ b/drivers/net/hyperv/netvsc_drv.c @@ -794,7 +794,7 @@ static struct sk_buff *netvsc_alloc_recv_skb(struct net_device *net, if (xbuf) { unsigned int hdroom = xdp->data - xdp->data_hard_start; unsigned int xlen = xdp->data_end - xdp->data; - unsigned int frag_size = netvsc_xdp_fraglen(hdroom + xlen); + unsigned int frag_size = xdp->frame_sz; skb = build_skb(xbuf, frag_size);
The hyperv NIC drivers XDP implementation is rather disappointing as it will be a slowdown to enable XDP on this driver, given it will allocate a new page for each packet and copy over the payload, before invoking the XDP BPF-prog. The positive thing it that its easy to determine the xdp.frame_sz. The XDP implementation for hv_netvsc transparently passes xdp_prog to the associated VF NIC. Many of the Azure VMs are using SRIOV, so majority of the data are actually processed directly on the VF driver's XDP path. So the overhead of the synthetic data path (hv_netvsc) is minimal. Then XDP is enabled on this driver, XDP_PASS and XDP_TX will create the SKB via build_skb (based on the newly allocated page). Now using XDP frame_sz this will provide more skb_tailroom, which netstack can use for SKB coalescing (e.g tcp_try_coalesce -> skb_try_coalesce). Cc: Wei Liu <wei.liu@kernel.org> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> --- drivers/net/hyperv/netvsc_bpf.c | 1 + drivers/net/hyperv/netvsc_drv.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-)