From: Jakub Kicinski <kuba@kernel.org>
To: Lorenzo Bianconi <lorenzo@kernel.org>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
lorenzo.bianconi@redhat.com, davem@davemloft.net, ast@kernel.org,
daniel@iogearbox.net, shayagr@amazon.com,
john.fastabend@gmail.com, dsahern@kernel.org, brouer@redhat.com,
echaudro@redhat.com, jasowang@redhat.com,
alexander.duyck@gmail.com, saeed@kernel.org,
maciej.fijalkowski@intel.com, magnus.karlsson@intel.com,
tirthendu.sarkar@intel.com, toke@redhat.com
Subject: Re: [PATCH v14 bpf-next 10/18] bpf: add multi-buff support to the bpf_xdp_adjust_tail() API
Date: Thu, 16 Sep 2021 09:55:44 -0700 [thread overview]
Message-ID: <20210916095544.50978cd0@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <e07aa987d148c168f1ac95a315d45e24e58c54f5.1631289870.git.lorenzo@kernel.org>
On Fri, 10 Sep 2021 18:14:16 +0200 Lorenzo Bianconi wrote:
> From: Eelco Chaudron <echaudro@redhat.com>
>
> This change adds support for tail growing and shrinking for XDP multi-buff.
>
> When called on a multi-buffer packet with a grow request, it will always
> work on the last fragment of the packet. So the maximum grow size is the
> last fragments tailroom, i.e. no new buffer will be allocated.
>
> When shrinking, it will work from the last fragment, all the way down to
> the base buffer depending on the shrinking size. It's important to mention
> that once you shrink down the fragment(s) are freed, so you can not grow
> again to the original size.
>
> Acked-by: John Fastabend <john.fastabend@gmail.com>
> Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
> +static inline unsigned int xdp_get_frag_tailroom(const skb_frag_t *frag)
> +{
> + struct page *page = skb_frag_page(frag);
> +
> + return page_size(page) - skb_frag_size(frag) - skb_frag_off(frag);
> +}
How do we deal with NICs which can pack multiple skbs into a page frag?
skb_shared_info field to mark the end of last fragment? Just want to make
sure there is a path to supporting such designs.
> +static int bpf_xdp_mb_adjust_tail(struct xdp_buff *xdp, int offset)
> +{
> + struct skb_shared_info *sinfo;
> +
> + sinfo = xdp_get_shared_info_from_buff(xdp);
> + if (offset >= 0) {
> + skb_frag_t *frag = &sinfo->frags[sinfo->nr_frags - 1];
> + int size;
> +
> + if (unlikely(offset > xdp_get_frag_tailroom(frag)))
> + return -EINVAL;
> +
> + size = skb_frag_size(frag);
> + memset(skb_frag_address(frag) + size, 0, offset);
> + skb_frag_size_set(frag, size + offset);
> + sinfo->xdp_frags_size += offset;
> + } else {
> + int i, n_frags_free = 0, len_free = 0, tlen_free = 0;
> +
> + offset = abs(offset);
> + if (unlikely(offset > ((int)(xdp->data_end - xdp->data) +
> + sinfo->xdp_frags_size - ETH_HLEN)))
> + return -EINVAL;
> +
> + for (i = sinfo->nr_frags - 1; i >= 0 && offset > 0; i--) {
> + skb_frag_t *frag = &sinfo->frags[i];
> + int size = skb_frag_size(frag);
> + int shrink = min_t(int, offset, size);
> +
> + len_free += shrink;
> + offset -= shrink;
> +
> + if (unlikely(size == shrink)) {
> + struct page *page = skb_frag_page(frag);
> +
> + __xdp_return(page_address(page), &xdp->rxq->mem,
> + false, NULL);
> + tlen_free += page_size(page);
> + n_frags_free++;
> + } else {
> + skb_frag_size_set(frag, size - shrink);
> + break;
> + }
> + }
> + sinfo->nr_frags -= n_frags_free;
> + sinfo->xdp_frags_size -= len_free;
> + sinfo->xdp_frags_truesize -= tlen_free;
> +
> + if (unlikely(offset > 0)) {
> + xdp_buff_clear_mb(xdp);
> + xdp->data_end -= offset;
> + }
> + }
> +
> + return 0;
> +}
nit: most of this function is indented, situation is ripe for splitting
it into two
next prev parent reply other threads:[~2021-09-16 17:44 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-10 16:14 [PATCH v14 bpf-next 00/18] mvneta: introduce XDP multi-buffer support Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 01/18] net: skbuff: add size metadata to skb_shared_info for xdp Lorenzo Bianconi
2021-09-10 16:18 ` Jesper Dangaard Brouer
2021-09-10 16:14 ` [PATCH v14 bpf-next 02/18] xdp: introduce flags field in xdp_buff/xdp_frame Lorenzo Bianconi
2021-09-10 16:19 ` Jesper Dangaard Brouer
2021-09-10 16:14 ` [PATCH v14 bpf-next 03/18] net: mvneta: update mb bit before passing the xdp buffer to eBPF layer Lorenzo Bianconi
2021-09-20 8:25 ` Shay Agroskin
2021-09-20 8:37 ` Lorenzo Bianconi
2021-09-20 8:45 ` Shay Agroskin
2021-09-20 9:00 ` Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 04/18] net: mvneta: simplify mvneta_swbm_add_rx_fragment management Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 05/18] net: xdp: add xdp_update_skb_shared_info utility routine Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 06/18] net: marvell: rely on " Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 07/18] xdp: add multi-buff support to xdp_return_{buff/frame} Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 08/18] net: mvneta: add multi buffer support to XDP_TX Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 09/18] net: mvneta: enable jumbo frames for XDP Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 10/18] bpf: add multi-buff support to the bpf_xdp_adjust_tail() API Lorenzo Bianconi
2021-09-16 16:55 ` Jakub Kicinski [this message]
2021-09-17 10:02 ` Lorenzo Bianconi
2021-09-17 13:03 ` Jakub Kicinski
2021-09-10 16:14 ` [PATCH v14 bpf-next 11/18] bpf: introduce bpf_xdp_get_buff_len helper Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 12/18] bpf: add multi-buffer support to xdp copy helpers Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 13/18] bpf: move user_size out of bpf_test_init Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 14/18] bpf: introduce multibuff support to bpf_prog_test_run_xdp() Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 15/18] bpf: test_run: add xdp_shared_info pointer in bpf_test_finish signature Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 16/18] bpf: update xdp_adjust_tail selftest to include multi-buffer Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 17/18] net: xdp: introduce bpf_xdp_adjust_data helper Lorenzo Bianconi
2021-09-10 16:14 ` [PATCH v14 bpf-next 18/18] bpf: add bpf_xdp_adjust_data selftest Lorenzo Bianconi
2021-09-16 16:55 ` [PATCH v14 bpf-next 00/18] mvneta: introduce XDP multi-buffer support Jakub Kicinski
2021-09-17 14:51 ` Lorenzo Bianconi
2021-09-17 18:33 ` Jakub Kicinski
2021-09-17 18:43 ` Alexei Starovoitov
2021-09-17 19:00 ` Jakub Kicinski
2021-09-17 19:10 ` Alexei Starovoitov
2021-09-17 22:07 ` John Fastabend
2021-09-18 11:53 ` Toke Høiland-Jørgensen
2021-09-20 18:02 ` Jakub Kicinski
2021-09-20 21:01 ` Toke Høiland-Jørgensen
2021-09-20 21:25 ` Jakub Kicinski
2021-09-20 22:44 ` Toke Høiland-Jørgensen
2021-09-21 10:03 ` Eelco Chaudron
2021-09-28 11:48 ` Magnus Karlsson
2021-09-29 10:36 ` Lorenz Bauer
2021-09-29 12:25 ` Toke Høiland-Jørgensen
2021-09-29 12:32 ` Lorenz Bauer
2021-09-29 17:48 ` Jakub Kicinski
2021-09-29 17:46 ` Jakub Kicinski
2021-09-29 10:41 ` Lorenz Bauer
2021-09-29 12:10 ` Toke Høiland-Jørgensen
2021-09-29 12:38 ` Lorenz Bauer
2021-09-29 18:54 ` Alexei Starovoitov
2021-09-29 19:22 ` Jakub Kicinski
2021-09-29 20:39 ` Toke Høiland-Jørgensen
2021-10-01 9:03 ` Lorenzo Bianconi
2021-10-01 18:35 ` Jakub Kicinski
2021-10-06 9:32 ` Lorenzo Bianconi
2021-10-06 10:08 ` Eelco Chaudron
2021-10-06 12:15 ` Lorenzo Bianconi
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