lkml.org 
[lkml]   [2019]   [Jul]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    SubjectRE: [PATCH net-next 3/3] net: stmmac: Introducing support for Page Pool
    Date
    From: Jon Hunter <jonathanh@nvidia.com>
    Date: Jul/25/2019, 14:20:07 (UTC+00:00)

    >
    > On 03/07/2019 11:37, Jose Abreu wrote:
    > > Mapping and unmapping DMA region is an high bottleneck in stmmac driver,
    > > specially in the RX path.
    > >
    > > This commit introduces support for Page Pool API and uses it in all RX
    > > queues. With this change, we get more stable troughput and some increase
    > > of banwidth with iperf:
    > > - MAC1000 - 950 Mbps
    > > - XGMAC: 9.22 Gbps
    > >
    > > Signed-off-by: Jose Abreu <joabreu@synopsys.com>
    > > Cc: Joao Pinto <jpinto@synopsys.com>
    > > Cc: David S. Miller <davem@davemloft.net>
    > > Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
    > > Cc: Alexandre Torgue <alexandre.torgue@st.com>
    > > Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
    > > Cc: Maxime Ripard <maxime.ripard@bootlin.com>
    > > Cc: Chen-Yu Tsai <wens@csie.org>
    > > ---
    > > drivers/net/ethernet/stmicro/stmmac/Kconfig | 1 +
    > > drivers/net/ethernet/stmicro/stmmac/stmmac.h | 10 +-
    > > drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 196 ++++++----------------
    > > 3 files changed, 63 insertions(+), 144 deletions(-)
    >
    > ...
    >
    > > @@ -3306,49 +3295,22 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue)
    > > else
    > > p = rx_q->dma_rx + entry;
    > >
    > > - if (likely(!rx_q->rx_skbuff[entry])) {
    > > - struct sk_buff *skb;
    > > -
    > > - skb = netdev_alloc_skb_ip_align(priv->dev, bfsize);
    > > - if (unlikely(!skb)) {
    > > - /* so for a while no zero-copy! */
    > > - rx_q->rx_zeroc_thresh = STMMAC_RX_THRESH;
    > > - if (unlikely(net_ratelimit()))
    > > - dev_err(priv->device,
    > > - "fail to alloc skb entry %d\n",
    > > - entry);
    > > - break;
    > > - }
    > > -
    > > - rx_q->rx_skbuff[entry] = skb;
    > > - rx_q->rx_skbuff_dma[entry] =
    > > - dma_map_single(priv->device, skb->data, bfsize,
    > > - DMA_FROM_DEVICE);
    > > - if (dma_mapping_error(priv->device,
    > > - rx_q->rx_skbuff_dma[entry])) {
    > > - netdev_err(priv->dev, "Rx DMA map failed\n");
    > > - dev_kfree_skb(skb);
    > > + if (!buf->page) {
    > > + buf->page = page_pool_dev_alloc_pages(rx_q->page_pool);
    > > + if (!buf->page)
    > > break;
    > > - }
    > > -
    > > - stmmac_set_desc_addr(priv, p, rx_q->rx_skbuff_dma[entry]);
    > > - stmmac_refill_desc3(priv, rx_q, p);
    > > -
    > > - if (rx_q->rx_zeroc_thresh > 0)
    > > - rx_q->rx_zeroc_thresh--;
    > > -
    > > - netif_dbg(priv, rx_status, priv->dev,
    > > - "refill entry #%d\n", entry);
    > > }
    > > - dma_wmb();
    > > +
    > > + buf->addr = buf->page->dma_addr;
    > > + stmmac_set_desc_addr(priv, p, buf->addr);
    > > + stmmac_refill_desc3(priv, rx_q, p);
    > >
    > > rx_q->rx_count_frames++;
    > > rx_q->rx_count_frames %= priv->rx_coal_frames;
    > > use_rx_wd = priv->use_riwt && rx_q->rx_count_frames;
    > >
    > > - stmmac_set_rx_owner(priv, p, use_rx_wd);
    > > -
    > > dma_wmb();
    > > + stmmac_set_rx_owner(priv, p, use_rx_wd);
    > >
    > > entry = STMMAC_GET_ENTRY(entry, DMA_RX_SIZE);
    > > }
    >
    > I was looking at this change in a bit closer detail and one thing that
    > stuck out to me was the above where the barrier had been moved from
    > after the stmmac_set_rx_owner() call to before.
    >
    > So I moved this back and I no longer saw the crash. However, then I
    > recalled I had the patch to enable the debug prints for the buffer
    > address applied but after reverting that, the crash occurred again.
    >
    > In other words, what works for me is moving the above barrier and adding
    > the debug print, which appears to suggest that there is some
    > timing/coherency issue here. Anyway, maybe this is clue to what is going
    > on?
    >
    > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
    > index a7486c2f3221..2f016397231b 100644
    > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
    > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
    > @@ -3303,8 +3303,8 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue)
    > rx_q->rx_count_frames %= priv->rx_coal_frames;
    > use_rx_wd = priv->use_riwt && rx_q->rx_count_frames;
    >
    > - dma_wmb();
    > stmmac_set_rx_owner(priv, p, use_rx_wd);
    > + dma_wmb();
    >
    > entry = STMMAC_GET_ENTRY(entry, DMA_RX_SIZE);
    > }
    > @@ -3438,6 +3438,10 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
    > dma_sync_single_for_device(priv->device, buf->addr,
    > frame_len, DMA_FROM_DEVICE);
    >
    > + pr_info("%s: paddr=0x%llx, vaddr=0x%llx, len=%d", __func__,
    > + buf->addr, page_address(buf->page),
    > + frame_len);
    > +
    > if (netif_msg_pktdata(priv)) {
    > netdev_dbg(priv->dev, "frame received (%dbytes)",
    > frame_len);
    >
    > Cheers
    > Jon
    >
    > --
    > nvpublic

    Well, I wasn't expecting that :/

    Per documentation of barriers I think we should set descriptor fields
    and then barrier and finally ownership to HW so that remaining fields
    are coherent before owner is set.

    Anyway, can you also add a dma_rmb() after the call to
    stmmac_rx_status() ?

    ---
    Thanks,
    Jose Miguel Abreu
    \
     
     \ /
      Last update: 2019-07-25 15:27    [W:4.363 / U:0.480 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site