From: David Miller <davem@davemloft.net>
To: haiyangz@microsoft.com
Cc: sashal@kernel.org, linux-hyperv@vger.kernel.org,
netdev@vger.kernel.org, kys@microsoft.com,
sthemmin@microsoft.com, olaf@aepfle.de, vkuznets@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2,net-next, 1/2] hv_netvsc: Add XDP support
Date: Tue, 21 Jan 2020 11:04:54 +0100 (CET) [thread overview]
Message-ID: <20200121.110454.2077433904156411260.davem@davemloft.net> (raw)
In-Reply-To: <1579558957-62496-2-git-send-email-haiyangz@microsoft.com>
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.
next prev parent reply other threads:[~2020-01-21 10:04 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 [this message]
2020-01-21 13:56 ` Haiyang Zhang
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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