Devmem TX charges each frag the net_iov size, PAGE_SIZE today: zerocopy_fill_skb_from_devmem() adds PAGE_SIZE to skb->truesize per frag and __zerocopy_sg_from_iter() charges it to sk_wmem_queued. TCP uncharges in bytes as acked data is trimmed from the skb (tcp_trim_head()) and uncharges the rest when the skb is freed. A frag shorter than a page leaves the difference charged until then, which is small with PAGE_SIZE net_iovs. TX net_iovs are about to grow up to 2MB, while frags stay bounded by the skb and many frags share a net_iov. Charging the net_iov size would charge up to 2MB per frag: a 64KB skb with two frags would charge 4MB and fill the default 4MB send buffer on its own. Charge the frag length instead, which also matches what TCP uncharges. Signed-off-by: Stanislav Fomichev Reviewed-by: Mina Almasry Reviewed-by: Dragos Tatulea --- net/core/datagram.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/datagram.c b/net/core/datagram.c index ecc30a6f8302..489d92fe6dae 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -737,7 +737,7 @@ zerocopy_fill_skb_from_devmem(struct sk_buff *skb, struct iov_iter *from, netmem_inc_ref(net_iov_to_netmem(niov)); skb_add_rx_frag_netmem(skb, i, net_iov_to_netmem(niov), off, - size, PAGE_SIZE); + size, size); iov_iter_advance(from, size); length -= size; i++; -- 2.53.0-Meta