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Subject[PATCH net-next 1/3] net: stmmac: Fix NAPI poll in TX path when in multi-queue
Date
Commit 8fce33317023 introduced the concept of NAPI per-channel and
independent cleaning of TX path.

This is currently breaking performance in some cases. The scenario
happens when all packets are being received in Queue 0 but the TX is
performed in Queue != 0.

Fix this by using different NAPI instances per each TX and RX queue, as
suggested by Florian.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Florian Fainelli <f.fainelli@gmail.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>
---
drivers/net/ethernet/stmicro/stmmac/stmmac.h | 5 +-
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 112 ++++++++++++----------
2 files changed, 64 insertions(+), 53 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 63e1064b27a2..e697ecd9b0a6 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -78,11 +78,10 @@ struct stmmac_rx_queue {
};

struct stmmac_channel {
- struct napi_struct napi ____cacheline_aligned_in_smp;
+ struct napi_struct rx_napi ____cacheline_aligned_in_smp;
+ struct napi_struct tx_napi ____cacheline_aligned_in_smp;
struct stmmac_priv *priv_data;
u32 index;
- int has_rx;
- int has_tx;
};

struct stmmac_tc_entry {
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 685d20472358..89a4dd75af76 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -155,7 +155,10 @@ static void stmmac_disable_all_queues(struct stmmac_priv *priv)
for (queue = 0; queue < maxq; queue++) {
struct stmmac_channel *ch = &priv->channel[queue];

- napi_disable(&ch->napi);
+ if (queue < rx_queues_cnt)
+ napi_disable(&ch->rx_napi);
+ if (queue < tx_queues_cnt)
+ napi_disable(&ch->tx_napi);
}
}

@@ -173,7 +176,10 @@ static void stmmac_enable_all_queues(struct stmmac_priv *priv)
for (queue = 0; queue < maxq; queue++) {
struct stmmac_channel *ch = &priv->channel[queue];

- napi_enable(&ch->napi);
+ if (queue < rx_queues_cnt)
+ napi_enable(&ch->rx_napi);
+ if (queue < tx_queues_cnt)
+ napi_enable(&ch->tx_napi);
}
}

@@ -1939,6 +1945,10 @@ static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue)
mod_timer(&priv->eee_ctrl_timer, STMMAC_LPI_T(eee_timer));
}

+ /* We still have pending packets, let's call for a new scheduling */
+ if (tx_q->dirty_tx != tx_q->cur_tx)
+ mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(10));
+
__netif_tx_unlock_bh(netdev_get_tx_queue(priv->dev, queue));

return count;
@@ -2029,23 +2039,15 @@ static int stmmac_napi_check(struct stmmac_priv *priv, u32 chan)
int status = stmmac_dma_interrupt_status(priv, priv->ioaddr,
&priv->xstats, chan);
struct stmmac_channel *ch = &priv->channel[chan];
- bool needs_work = false;
-
- if ((status & handle_rx) && ch->has_rx) {
- needs_work = true;
- } else {
- status &= ~handle_rx;
- }

- if ((status & handle_tx) && ch->has_tx) {
- needs_work = true;
- } else {
- status &= ~handle_tx;
+ if ((status & handle_rx) && (chan < priv->plat->rx_queues_to_use)) {
+ stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
+ napi_schedule_irqoff(&ch->rx_napi);
}

- if (needs_work && napi_schedule_prep(&ch->napi)) {
+ if ((status & handle_tx) && (chan < priv->plat->tx_queues_to_use)) {
stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
- __napi_schedule(&ch->napi);
+ napi_schedule_irqoff(&ch->tx_napi);
}

return status;
@@ -2241,8 +2243,14 @@ static void stmmac_tx_timer(struct timer_list *t)

ch = &priv->channel[tx_q->queue_index];

- if (likely(napi_schedule_prep(&ch->napi)))
- __napi_schedule(&ch->napi);
+ /*
+ * If NAPI is already running we can miss some events. Let's rearm
+ * the timer and try again.
+ */
+ if (likely(napi_schedule_prep(&ch->tx_napi)))
+ __napi_schedule(&ch->tx_napi);
+ else
+ mod_timer(&tx_q->txtimer, STMMAC_COAL_TIMER(10));
}

/**
@@ -3498,7 +3506,7 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
else
skb->ip_summed = CHECKSUM_UNNECESSARY;

- napi_gro_receive(&ch->napi, skb);
+ napi_gro_receive(&ch->rx_napi, skb);

priv->dev->stats.rx_packets++;
priv->dev->stats.rx_bytes += frame_len;
@@ -3513,41 +3521,41 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
return count;
}

-/**
- * stmmac_poll - stmmac poll method (NAPI)
- * @napi : pointer to the napi structure.
- * @budget : maximum number of packets that the current CPU can receive from
- * all interfaces.
- * Description :
- * To look at the incoming frames and clear the tx resources.
- */
-static int stmmac_napi_poll(struct napi_struct *napi, int budget)
+static int stmmac_napi_poll_rx(struct napi_struct *napi, int budget)
{
struct stmmac_channel *ch =
- container_of(napi, struct stmmac_channel, napi);
+ container_of(napi, struct stmmac_channel, rx_napi);
struct stmmac_priv *priv = ch->priv_data;
- int work_done, rx_done = 0, tx_done = 0;
u32 chan = ch->index;
+ int work_done;

priv->xstats.napi_poll++;

- if (ch->has_tx)
- tx_done = stmmac_tx_clean(priv, budget, chan);
- if (ch->has_rx)
- rx_done = stmmac_rx(priv, budget, chan);
+ work_done = stmmac_rx(priv, budget, chan);
+ if (work_done < budget && napi_complete_done(napi, work_done))
+ stmmac_enable_dma_irq(priv, priv->ioaddr, chan);
+ return work_done;
+}

- work_done = max(rx_done, tx_done);
- work_done = min(work_done, budget);
+static int stmmac_napi_poll_tx(struct napi_struct *napi, int budget)
+{
+ struct stmmac_channel *ch =
+ container_of(napi, struct stmmac_channel, tx_napi);
+ struct stmmac_priv *priv = ch->priv_data;
+ struct stmmac_tx_queue *tx_q;
+ u32 chan = ch->index;
+ int work_done;

- if (work_done < budget && napi_complete_done(napi, work_done)) {
- int stat;
+ priv->xstats.napi_poll++;

+ work_done = stmmac_tx_clean(priv, budget, chan);
+ if (work_done < budget && napi_complete_done(napi, work_done))
stmmac_enable_dma_irq(priv, priv->ioaddr, chan);
- stat = stmmac_dma_interrupt_status(priv, priv->ioaddr,
- &priv->xstats, chan);
- if (stat && napi_reschedule(napi))
- stmmac_disable_dma_irq(priv, priv->ioaddr, chan);
- }
+
+ /* Force transmission restart */
+ tx_q = &priv->tx_queue[chan];
+ stmmac_enable_dma_transmission(priv, priv->ioaddr);
+ stmmac_set_tx_tail_ptr(priv, priv->ioaddr, tx_q->tx_tail_addr, chan);

return work_done;
}
@@ -4323,13 +4331,14 @@ int stmmac_dvr_probe(struct device *device,
ch->priv_data = priv;
ch->index = queue;

- if (queue < priv->plat->rx_queues_to_use)
- ch->has_rx = true;
- if (queue < priv->plat->tx_queues_to_use)
- ch->has_tx = true;
-
- netif_napi_add(ndev, &ch->napi, stmmac_napi_poll,
- NAPI_POLL_WEIGHT);
+ if (queue < priv->plat->rx_queues_to_use) {
+ netif_napi_add(ndev, &ch->rx_napi, stmmac_napi_poll_rx,
+ NAPI_POLL_WEIGHT);
+ }
+ if (queue < priv->plat->tx_queues_to_use) {
+ netif_napi_add(ndev, &ch->tx_napi, stmmac_napi_poll_tx,
+ NAPI_POLL_WEIGHT);
+ }
}

mutex_init(&priv->lock);
@@ -4385,7 +4394,10 @@ int stmmac_dvr_probe(struct device *device,
for (queue = 0; queue < maxq; queue++) {
struct stmmac_channel *ch = &priv->channel[queue];

- netif_napi_del(&ch->napi);
+ if (queue < priv->plat->rx_queues_to_use)
+ netif_napi_del(&ch->rx_napi);
+ if (queue < priv->plat->tx_queues_to_use)
+ netif_napi_del(&ch->tx_napi);
}
error_hw_init:
destroy_workqueue(priv->wq);
--
2.7.4
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