From: Haiyang Zhang <haiyangz@microsoft.com>
To: David Miller <davem@davemloft.net>
Cc: "sashal@kernel.org" <sashal@kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
KY Srinivasan <kys@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
"olaf@aepfle.de" <olaf@aepfle.de>, vkuznets <vkuznets@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH V2,net-next, 1/2] hv_netvsc: Add XDP support
Date: Tue, 21 Jan 2020 13:56:54 +0000 [thread overview]
Message-ID: <MN2PR21MB1375A2A91EDBD8E63CBDA2F4CA0D0@MN2PR21MB1375.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20200121.110454.2077433904156411260.davem@davemloft.net>
> -----Original Message-----
> From: linux-hyperv-owner@vger.kernel.org <linux-hyperv-
> owner@vger.kernel.org> On Behalf Of David Miller
> Sent: Tuesday, January 21, 2020 5:05 AM
> To: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: sashal@kernel.org; linux-hyperv@vger.kernel.org; netdev@vger.kernel.org;
> KY Srinivasan <kys@microsoft.com>; Stephen Hemminger
> <sthemmin@microsoft.com>; olaf@aepfle.de; vkuznets
> <vkuznets@redhat.com>; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH V2,net-next, 1/2] hv_netvsc: Add XDP support
>
> From: Haiyang Zhang <haiyangz@microsoft.com>
> Date: Mon, 20 Jan 2020 14:22:36 -0800
>
> > +u32 netvsc_run_xdp(struct net_device *ndev, struct netvsc_channel *nvchan,
> > + struct xdp_buff *xdp)
> > +{
> > + struct page *page = NULL;
> > + void *data = nvchan->rsc.data[0];
> > + u32 len = nvchan->rsc.len[0];
> > + struct bpf_prog *prog;
> > + u32 act = XDP_PASS;
>
> Please use reverse christmas tree ordering of local variables.
>
> > + xdp->data_hard_start = page_address(page);
> > + xdp->data = xdp->data_hard_start + NETVSC_XDP_HDRM;
> > + xdp_set_data_meta_invalid(xdp);
> > + xdp->data_end = xdp->data + len;
> > + xdp->rxq = &nvchan->xdp_rxq;
> > + xdp->handle = 0;
> > +
> > + memcpy(xdp->data, data, len);
>
> Why can't the program run directly on nvchan->rsc.data[0]?
>
> This data copy defeats the whole performance gain of using XDP.
Sure I will update this, and the var order.
Thanks
- Haiyang
next prev parent reply other threads:[~2020-01-21 13:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-20 22:22 [PATCH V2,net-next, 0/2] hv_netvsc: Add XDP support Haiyang Zhang
2020-01-20 22:22 ` [PATCH V2,net-next, 1/2] " Haiyang Zhang
2020-01-21 10:04 ` David Miller
2020-01-21 13:56 ` Haiyang Zhang [this message]
2020-01-21 18:53 ` Haiyang Zhang
2020-01-21 21:28 ` David Miller
2020-01-22 2:12 ` Haiyang Zhang
2020-01-20 22:22 ` [PATCH V2,net-next, 2/2] hv_netvsc: Update document for " Haiyang Zhang
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