netdev - RE: [Intel-wired-lan] [PATCH v4 net-next 1/9] i40e: don't reserve excessive XDP_PACKET

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Message-ID: <DM6PR11MB329239287A3AC0FFC21A3DEEF1239@DM6PR11MB3292.namprd11.prod.outlook.com>
Date:   Sat, 29 Jan 2022 08:55:15 +0000
From:   "Bhandare, KiranX" <kiranx.bhandare@...el.com>
To:     "Lobakin, Alexandr" <alexandr.lobakin@...el.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC:     Song Liu <songliubraving@...com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        "Andrii Nakryiko" <andrii@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Jakub Kicinski" <kuba@...nel.org>, KP Singh <kpsingh@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [Intel-wired-lan] [PATCH v4 net-next 1/9] i40e: don't reserve
 excessive XDP_PACKET_HEADROOM on XSK Rx to skb


> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of
> Alexander Lobakin
> Sent: Wednesday, December 8, 2021 7:37 PM
> To: intel-wired-lan@...ts.osuosl.org
> Cc: Song Liu <songliubraving@...com>; Jesper Dangaard Brouer
> <hawk@...nel.org>; Daniel Borkmann <daniel@...earbox.net>; Yonghong
> Song <yhs@...com>; Martin KaFai Lau <kafai@...com>; John Fastabend
> <john.fastabend@...il.com>; Alexei Starovoitov <ast@...nel.org>; Andrii
> Nakryiko <andrii@...nel.org>; Björn Töpel <bjorn@...nel.org>;
> netdev@...r.kernel.org; Jakub Kicinski <kuba@...nel.org>; KP Singh
> <kpsingh@...nel.org>; bpf@...r.kernel.org; David S. Miller
> <davem@...emloft.net>; linux-kernel@...r.kernel.org
> Subject: [Intel-wired-lan] [PATCH v4 net-next 1/9] i40e: don't reserve
> excessive XDP_PACKET_HEADROOM on XSK Rx to skb
> 
> {__,}napi_alloc_skb() allocates and reserves additional NET_SKB_PAD
> + NET_IP_ALIGN for any skb.
> OTOH, i40e_construct_skb_zc() currently allocates and reserves additional
> `xdp->data - xdp->data_hard_start`, which is XDP_PACKET_HEADROOM for
> XSK frames.
> There's no need for that at all as the frame is post-XDP and will go only to the
> networking stack core.
> Pass the size of the actual data only to __napi_alloc_skb() and don't reserve
> anything. This will give enough headroom for stack processing.
> 
> Fixes: 0a714186d3c0 ("i40e: add AF_XDP zero-copy Rx support")
> Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_xsk.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 

Tested-by: Kiran Bhandare <kiranx.bhandare@...el.com>  A Contingent Worker at Intel