> On 2023/4/23 2:54, Lorenzo Bianconi wrote:
> > struct veth_priv {
> > @@ -727,17 +729,20 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
> > goto drop;
> >
> > /* Allocate skb head */
> > - page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
> > + page = page_pool_dev_alloc_pages(rq->page_pool);
> > if (!page)
> > goto drop;
> >
> > nskb = build_skb(page_address(page), PAGE_SIZE);
>
> If page pool is used with PP_FLAG_PAGE_FRAG, maybe there is some additional
> improvement for the MTU 1500B case, it seem a 4K page is able to hold two skb.
> And we can reduce the memory usage too, which is a significant saving if page
> size is 64K.
please correct if I am wrong but I think the 1500B MTU case does not fit in the
half-page buffer size since we need to take into account VETH_XDP_HEADROOM.
In particular:
- VETH_BUF_SIZE = 2048
- VETH_XDP_HEADROOM = 256 + 2 = 258
- max_headsize = SKB_WITH_OVERHEAD(VETH_BUF_SIZE - VETH_XDP_HEADROOM) = 1470
Even in this case we will need the consume a full page. In fact, performances
are a little bit worse:
MTU 1500: tcp throughput ~ 8.3Gbps
Do you agree or am I missing something?
Regards,
Lorenzo
>
>
> > if (!nskb) {
> > - put_page(page);
> > + page_pool_put_full_page(rq->page_pool, page, true);
> > goto drop;
> > }
> >
> > skb_reserve(nskb, VETH_XDP_HEADROOM);
> > + skb_copy_header(nskb, skb);
> > + skb_mark_for_recycle(nskb);
> > +
> > size = min_t(u32, skb->len, max_head_size);
> > if (skb_copy_bits(skb, 0, nskb->data, size)) {
> > consume_skb(nskb);
> > @@ -745,7 +750,6 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
> > }
> > skb_put(nskb, size);
> >
> > - skb_copy_header(nskb, skb);
> > head_off = skb_headroom(nskb) - skb_headroom(skb);
> > skb_headers_offset_update(nskb, head_off);
> >
> > @@ -754,7 +758,7 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
> > len = skb->len - off;
> >
> > for (i = 0; i < MAX_SKB_FRAGS && off < skb->len; i++) {
> > - page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
> > + page = page_pool_dev_alloc_pages(rq->page_pool);
> > if (!page) {
> > consume_skb(nskb);
> > goto drop;
> > @@ -1002,11 +1006,37 @@ static int veth_poll(struct napi_struct *napi, int budget)
> > return done;
> > }
> >
> > +static int veth_create_page_pool(struct veth_rq *rq)
> > +{
> > + struct page_pool_params pp_params = {
> > + .order = 0,
> > + .pool_size = VETH_RING_SIZE,
>
> It seems better to allocate different poo_size according to
> the mtu, so that the best proformance is achiced using the
> least memory?
>
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