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igc: 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, igc_construct_skb_zc() currently allocates and reserves
additional `xdp->data_meta - xdp->data_hard_start`, which is about
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 (+ meta) to
__napi_alloc_skb() and don't reserve anything. This will give
enough headroom for stack processing.
Also, net_prefetch() xdp->data_meta and align the copy size to
speed-up memcpy() a little and better match igc_construct_skb().

Fixes: fc9df2a0b5 ("igc: Enable RX via AF_XDP zero-copy")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Nechama Kraus <nechamax.kraus@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
This commit is contained in:
Alexander Lobakin 2021-12-08 15:06:59 +01:00 committed by Tony Nguyen
parent 45a34ca680
commit f9e61d365b
1 changed files with 7 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/net/ethernet/intel/igc/igc_main.c
View File

@ -2446,19 +2446,20 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
static struct sk_buff *igc_construct_skb_zc(struct igc_ring *ring,
struct xdp_buff *xdp)
{
unsigned int totalsize = xdp->data_end - xdp->data_meta;
unsigned int metasize = xdp->data - xdp->data_meta;
unsigned int datasize = xdp->data_end - xdp->data;
unsigned int totalsize = metasize + datasize;
struct sk_buff *skb;
skb = __napi_alloc_skb(&ring->q_vector->napi,
xdp->data_end - xdp->data_hard_start,
net_prefetch(xdp->data_meta);
skb = __napi_alloc_skb(&ring->q_vector->napi, totalsize,
GFP_ATOMIC | __GFP_NOWARN);
if (unlikely(!skb))
return NULL;
skb_reserve(skb, xdp->data_meta - xdp->data_hard_start);
memcpy(__skb_put(skb, totalsize), xdp->data_meta, totalsize);
memcpy(__skb_put(skb, totalsize), xdp->data_meta,
ALIGN(totalsize, sizeof(long)));
if (metasize) {
skb_metadata_set(skb, metasize);
__skb_pull(skb, metasize);