On Fri, Jun 3, 2022 at 2:03 AM Chen Lin <[email protected]> wrote:
>
> When rx_flag == MTK_RX_FLAGS_HWLRO,
> rx_data_len = MTK_MAX_LRO_RX_LENGTH(4096 * 3) > PAGE_SIZE.
> netdev_alloc_frag is for alloction of page fragment only.
> Reference to other drivers and Documentation/vm/page_frags.rst
>
> Branch to use alloc_pages when ring->frag_size > PAGE_SIZE.
>
> Signed-off-by: Chen Lin <[email protected]>
> ---
> drivers/net/ethernet/mediatek/mtk_eth_soc.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index b3b3c07..772d903 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -1467,7 +1467,16 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
> goto release_desc;
>
> /* alloc new buffer */
> - new_data = napi_alloc_frag(ring->frag_size);
> + if (ring->frag_size <= PAGE_SIZE) {
> + new_data = napi_alloc_frag(ring->frag_size);
> + } else {
> + struct page *page;
> + unsigned int order = get_order(ring->frag_size);
> +
> + page = alloc_pages(GFP_ATOMIC | __GFP_COMP |
> + __GFP_NOWARN, order);
> + new_data = page ? page_address(page) : NULL;
> + }
> if (unlikely(!new_data)) {
> netdev->stats.rx_dropped++;
> goto release_desc;
> @@ -1914,7 +1923,16 @@ static int mtk_rx_alloc(struct mtk_eth *eth, int ring_no, int rx_flag)
> return -ENOMEM;
>
> for (i = 0; i < rx_dma_size; i++) {
> - ring->data[i] = netdev_alloc_frag(ring->frag_size);
> + if (ring->frag_size <= PAGE_SIZE) {
> + ring->data[i] = netdev_alloc_frag(ring->frag_size);
> + } else {
> + struct page *page;
> + unsigned int order = get_order(ring->frag_size);
> +
> + page = alloc_pages(GFP_KERNEL | __GFP_COMP |
> + __GFP_NOWARN, order);
> + ring->data[i] = page ? page_address(page) : NULL;
> + }
> if (!ring->data[i])
> return -ENOMEM;
> }
Actually I looked closer at this driver. Is it able to receive frames
larger than 2K? If not there isn't any point in this change.
Based on commit 4fd59792097a ("net: ethernet: mediatek: support
setting MTU") it looks like it doesn't, so odds are this patch is not
necessary.
On Fri, Jun 3, 2022 at 8:25 AM Alexander Duyck
<[email protected]> wrote:
>
> On Fri, Jun 3, 2022 at 2:03 AM Chen Lin <[email protected]> wrote:
> >
> > When rx_flag == MTK_RX_FLAGS_HWLRO,
> > rx_data_len = MTK_MAX_LRO_RX_LENGTH(4096 * 3) > PAGE_SIZE.
> > netdev_alloc_frag is for alloction of page fragment only.
> > Reference to other drivers and Documentation/vm/page_frags.rst
> >
> > Branch to use alloc_pages when ring->frag_size > PAGE_SIZE.
> >
> > Signed-off-by: Chen Lin <[email protected]>
> > ---
> > drivers/net/ethernet/mediatek/mtk_eth_soc.c | 22 ++++++++++++++++++++--
> > 1 file changed, 20 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > index b3b3c07..772d903 100644
> > --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > @@ -1467,7 +1467,16 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
> > goto release_desc;
> >
> > /* alloc new buffer */
> > - new_data = napi_alloc_frag(ring->frag_size);
> > + if (ring->frag_size <= PAGE_SIZE) {
> > + new_data = napi_alloc_frag(ring->frag_size);
> > + } else {
> > + struct page *page;
> > + unsigned int order = get_order(ring->frag_size);
> > +
> > + page = alloc_pages(GFP_ATOMIC | __GFP_COMP |
> > + __GFP_NOWARN, order);
> > + new_data = page ? page_address(page) : NULL;
> > + }
> > if (unlikely(!new_data)) {
> > netdev->stats.rx_dropped++;
> > goto release_desc;
> > @@ -1914,7 +1923,16 @@ static int mtk_rx_alloc(struct mtk_eth *eth, int ring_no, int rx_flag)
> > return -ENOMEM;
> >
> > for (i = 0; i < rx_dma_size; i++) {
> > - ring->data[i] = netdev_alloc_frag(ring->frag_size);
> > + if (ring->frag_size <= PAGE_SIZE) {
> > + ring->data[i] = netdev_alloc_frag(ring->frag_size);
> > + } else {
> > + struct page *page;
> > + unsigned int order = get_order(ring->frag_size);
> > +
> > + page = alloc_pages(GFP_KERNEL | __GFP_COMP |
> > + __GFP_NOWARN, order);
> > + ring->data[i] = page ? page_address(page) : NULL;
> > + }
> > if (!ring->data[i])
> > return -ENOMEM;
> > }
>
> Actually I looked closer at this driver. Is it able to receive frames
> larger than 2K? If not there isn't any point in this change.
>
> Based on commit 4fd59792097a ("net: ethernet: mediatek: support
> setting MTU") it looks like it doesn't, so odds are this patch is not
> necessary.
I spoke too soon. I had overlooked the LRO part. With that being the
case you can probably optimize this code to do away with the get_order
piece entirely, at least during runtime. My main concern is that doing
that in the fast-path will be expensive so you would be much better
off doing something like
get_order(mtk_max_frag_size(MTK_RX_FLAGS_HWLRO)) which would be
converted into a constant at compile time since everything else would
be less than 1 page in size.
Also you could then replace alloc_pages with __get_free_pages which
would take care of the page_address call for you.