linux-kernel - RE: [Intel-wired-lan] [PATCH v4 net-next 8/9] ixgbe: don't reserve excessive XDP_PACKET

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Message-ID: <MW3PR11MB45546CBEB4E1427EA5CD65C99C519@MW3PR11MB4554.namprd11.prod.outlook.com>
Date:   Tue, 11 Jan 2022 11:51:46 +0000
From:   "Penigalapati, Sandeep" <sandeep.penigalapati@...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 8/9] ixgbe: 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 8/9] ixgbe: 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, ixgbe_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: d0bcacd0a130 ("ixgbe: 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/ixgbe/ixgbe_xsk.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@...el.com>