From: Stephen Hemminger <stephen@networkplumber.org>
To: Ofer Dagan <ofer.d@claroty.com>
Cc: users@dpdk.org
Subject: Re: Support jumbo packets with XDP
Date: Sun, 2 Feb 2025 09:32:55 -0800 [thread overview]
Message-ID: <20250202093255.19da8189@hermes.local> (raw)
In-Reply-To: <CAJZ4YbNsNpbLSGhOvo07U_iZexmVKDZoJhb9m0t-Sx74+5CLgQ@mail.gmail.com>
On Sun, 2 Feb 2025 08:53:42 +0200
Ofer Dagan <ofer.d@claroty.com> wrote:
> Hi all,
>
> We are trying to start using AF_XDP instead of libpcap (for use cases where
> dpdk drivers aren't a good fit for us). When using XDP, we can't set high
> MTU. How to still support jumbo packets in our application?
>
> Thanks,
> Ofer
What error are you seeing?
What version of DPDK, and what version of kernel are you building for.
The current version of AF_XDP Poll mode driver supports larger mtu sizes.
It is constrained because the receive buffer has to fit on a single page
and there is overhead for the various headers.
dev_info->min_mtu = RTE_ETHER_MIN_MTU;
#if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG)
dev_info->max_rx_pktlen = getpagesize() -
sizeof(struct rte_mempool_objhdr) -
sizeof(struct rte_mbuf) -
RTE_PKTMBUF_HEADROOM - XDP_PACKET_HEADROOM;
#else
dev_info->max_rx_pktlen = ETH_AF_XDP_FRAME_SIZE - XDP_PACKET_HEADROOM;
#endif
dev_info->max_mtu = dev_info->max_rx_pktlen - ETH_AF_XDP_ETH_OVERHEAD;
If you have a relatively recent kernel the UNALIGNED_CHUNK_FLAG should be set.
Stepping through the maths for that
max_rx_pktlen = 4096 - 24 - 128 - 128 - 256 = 3560
max_mtu = max_rx_pktlen - 14 - 4 = 3542
next prev parent reply other threads:[~2025-02-02 17:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-02 6:53 Ofer Dagan
2025-02-02 17:32 ` Stephen Hemminger [this message]
2025-02-03 7:16 ` [EXTERNAL] " Ofer Dagan
2025-02-04 2:43 ` Stephen Hemminger
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