Messages in this thread | | | From | Alexander Lobakin <> | Subject | Re: [PATCH 3/5] net: ethernet: mtk_eth_soc: work around issue with sending small fragments | Date | Thu, 24 Nov 2022 18:54:10 +0100 |
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From: Felix Fietkau <nbd@nbd.name> Date: Wed, 23 Nov 2022 10:57:52 +0100
> When frames are sent with very small fragments, the DMA engine appears to > lock up and transmit attempts time out. Fix this by detecting the presence > of small fragments and use skb_gso_segment + skb_linearize to deal with > them
Nit: all of your commit messages don't have a trailing dot (.), not sure if it's important, but my eye is missing it definitely :D
skb_gso_segment() and skb_linearize() are slow as hell. I think you can do it differently. I guess only the first (head) and the last frag can be so small, right?
So, if a frag from shinfo->frags is less than 16, get a new frag of the minimum acceptable size via netdev_alloc_frag(), copy the data to it and pad the rest with zeroes. Then increase skb->len and skb->data_len, skb_frag_unref() the current, "invalid" frag and replace the pointer to the new frag. I didn't miss anything I believe... Zero padding the tail is usual thing for NICs. skb frag substitution is less common, but should be legit.
If skb_headlen() is less than 16, try doing pskb_may_pull() + __skb_pull() at first. The argument would be `16 - headlen`. If pskb_may_pull() returns false, then yeah, you have no choice other than segmenting and linearizing ._.
> > Signed-off-by: Felix Fietkau <nbd@nbd.name> > --- > drivers/net/ethernet/mediatek/mtk_eth_soc.c | 36 +++++++++++++++++++-- > 1 file changed, 34 insertions(+), 2 deletions(-)
[...]
> if (unlikely(atomic_read(&ring->free_count) <= ring->thresh)) > netif_tx_stop_all_queues(dev); > -- > 2.38.1
Thanks, Olek
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