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Message-Id: <20211007162534.1502578-3-jeroendb@google.com>
Date: Thu, 7 Oct 2021 09:25:30 -0700
From: Jeroen de Borst <jeroendb@...gle.com>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org,
Tao Liu <xliutaox@...gle.com>,
Catherine Sullivan <csully@...gle.com>
Subject: [PATCH net-next 3/7] gve: Do lazy cleanup in TX path
From: Tao Liu <xliutaox@...gle.com>
When TX queue is full, attemt to process enough TX completions
to avoid stalling the queue.
Fixes: f5cedc84a30d2 ("gve: Add transmit and receive support")
Signed-off-by: Tao Liu <xliutaox@...gle.com>
Signed-off-by: Catherine Sullivan <csully@...gle.com>
---
drivers/net/ethernet/google/gve/gve.h | 9 +-
drivers/net/ethernet/google/gve/gve_ethtool.c | 3 +-
drivers/net/ethernet/google/gve/gve_main.c | 6 +-
drivers/net/ethernet/google/gve/gve_tx.c | 94 +++++++++++--------
4 files changed, 62 insertions(+), 50 deletions(-)
diff --git a/drivers/net/ethernet/google/gve/gve.h b/drivers/net/ethernet/google/gve/gve.h
index 59c525800e5d..003b30b91c6d 100644
--- a/drivers/net/ethernet/google/gve/gve.h
+++ b/drivers/net/ethernet/google/gve/gve.h
@@ -341,8 +341,8 @@ struct gve_tx_ring {
union {
/* GQI fields */
struct {
- /* NIC tail pointer */
- __be32 last_nic_done;
+ /* Spinlock for when cleanup in progress */
+ spinlock_t clean_lock;
};
/* DQO fields. */
@@ -821,8 +821,9 @@ netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev);
bool gve_tx_poll(struct gve_notify_block *block, int budget);
int gve_tx_alloc_rings(struct gve_priv *priv);
void gve_tx_free_rings_gqi(struct gve_priv *priv);
-__be32 gve_tx_load_event_counter(struct gve_priv *priv,
- struct gve_tx_ring *tx);
+u32 gve_tx_load_event_counter(struct gve_priv *priv,
+ struct gve_tx_ring *tx);
+bool gve_tx_clean_pending(struct gve_priv *priv, struct gve_tx_ring *tx);
/* rx handling */
void gve_rx_write_doorbell(struct gve_priv *priv, struct gve_rx_ring *rx);
int gve_rx_poll(struct gve_notify_block *block, int budget);
diff --git a/drivers/net/ethernet/google/gve/gve_ethtool.c b/drivers/net/ethernet/google/gve/gve_ethtool.c
index 716e6240305d..618a3e1d858e 100644
--- a/drivers/net/ethernet/google/gve/gve_ethtool.c
+++ b/drivers/net/ethernet/google/gve/gve_ethtool.c
@@ -330,8 +330,7 @@ gve_get_ethtool_stats(struct net_device *netdev,
data[i++] = tmp_tx_bytes;
data[i++] = tx->wake_queue;
data[i++] = tx->stop_queue;
- data[i++] = be32_to_cpu(gve_tx_load_event_counter(priv,
- tx));
+ data[i++] = gve_tx_load_event_counter(priv, tx);
data[i++] = tx->dma_mapping_error;
/* stats from NIC */
if (skip_nic_stats) {
diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 388262c61b8d..74e35a87ec38 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -201,13 +201,13 @@ static int gve_napi_poll(struct napi_struct *napi, int budget)
irq_doorbell = gve_irq_doorbell(priv, block);
iowrite32be(GVE_IRQ_ACK | GVE_IRQ_EVENT, irq_doorbell);
- /* Double check we have no extra work.
- * Ensure unmask synchronizes with checking for work.
+ /* Ensure IRQ ACK is visible before we check pending work.
+ * If queue had issued updates, it would be truly visible.
*/
mb();
if (block->tx)
- reschedule |= gve_tx_poll(block, -1);
+ reschedule |= gve_tx_clean_pending(priv, block->tx);
if (block->rx)
reschedule |= gve_rx_work_pending(block->rx);
diff --git a/drivers/net/ethernet/google/gve/gve_tx.c b/drivers/net/ethernet/google/gve/gve_tx.c
index 9922ce46a635..a9cb241fedf4 100644
--- a/drivers/net/ethernet/google/gve/gve_tx.c
+++ b/drivers/net/ethernet/google/gve/gve_tx.c
@@ -144,7 +144,7 @@ static void gve_tx_free_ring(struct gve_priv *priv, int idx)
gve_tx_remove_from_block(priv, idx);
slots = tx->mask + 1;
- gve_clean_tx_done(priv, tx, tx->req, false);
+ gve_clean_tx_done(priv, tx, priv->tx_desc_cnt, false);
netdev_tx_reset_queue(tx->netdev_txq);
dma_free_coherent(hdev, sizeof(*tx->q_resources),
@@ -176,6 +176,7 @@ static int gve_tx_alloc_ring(struct gve_priv *priv, int idx)
/* Make sure everything is zeroed to start */
memset(tx, 0, sizeof(*tx));
+ spin_lock_init(&tx->clean_lock);
tx->q_num = idx;
tx->mask = slots - 1;
@@ -328,10 +329,16 @@ static inline bool gve_can_tx(struct gve_tx_ring *tx, int bytes_required)
return (gve_tx_avail(tx) >= MAX_TX_DESC_NEEDED && can_alloc);
}
+static_assert(NAPI_POLL_WEIGHT >= MAX_TX_DESC_NEEDED);
+
/* Stops the queue if the skb cannot be transmitted. */
-static int gve_maybe_stop_tx(struct gve_tx_ring *tx, struct sk_buff *skb)
+static int gve_maybe_stop_tx(struct gve_priv *priv, struct gve_tx_ring *tx,
+ struct sk_buff *skb)
{
int bytes_required = 0;
+ u32 nic_done;
+ u32 to_do;
+ int ret;
if (!tx->raw_addressing)
bytes_required = gve_skb_fifo_bytes_required(tx, skb);
@@ -339,29 +346,28 @@ static int gve_maybe_stop_tx(struct gve_tx_ring *tx, struct sk_buff *skb)
if (likely(gve_can_tx(tx, bytes_required)))
return 0;
- /* No space, so stop the queue */
- tx->stop_queue++;
- netif_tx_stop_queue(tx->netdev_txq);
- smp_mb(); /* sync with restarting queue in gve_clean_tx_done() */
-
- /* Now check for resources again, in case gve_clean_tx_done() freed
- * resources after we checked and we stopped the queue after
- * gve_clean_tx_done() checked.
- *
- * gve_maybe_stop_tx() gve_clean_tx_done()
- * nsegs/can_alloc test failed
- * gve_tx_free_fifo()
- * if (tx queue stopped)
- * netif_tx_queue_wake()
- * netif_tx_stop_queue()
- * Need to check again for space here!
- */
- if (likely(!gve_can_tx(tx, bytes_required)))
- return -EBUSY;
+ ret = -EBUSY;
+ spin_lock(&tx->clean_lock);
+ nic_done = gve_tx_load_event_counter(priv, tx);
+ to_do = nic_done - tx->done;
- netif_tx_start_queue(tx->netdev_txq);
- tx->wake_queue++;
- return 0;
+ /* Only try to clean if there is hope for TX */
+ if (to_do + gve_tx_avail(tx) >= MAX_TX_DESC_NEEDED) {
+ if (to_do > 0) {
+ to_do = min_t(u32, to_do, NAPI_POLL_WEIGHT);
+ gve_clean_tx_done(priv, tx, to_do, false);
+ }
+ if (likely(gve_can_tx(tx, bytes_required)))
+ ret = 0;
+ }
+ if (ret) {
+ /* No space, so stop the queue */
+ tx->stop_queue++;
+ netif_tx_stop_queue(tx->netdev_txq);
+ }
+ spin_unlock(&tx->clean_lock);
+
+ return ret;
}
static void gve_tx_fill_pkt_desc(union gve_tx_desc *pkt_desc,
@@ -576,7 +582,7 @@ netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev)
WARN(skb_get_queue_mapping(skb) >= priv->tx_cfg.num_queues,
"skb queue index out of range");
tx = &priv->tx[skb_get_queue_mapping(skb)];
- if (unlikely(gve_maybe_stop_tx(tx, skb))) {
+ if (unlikely(gve_maybe_stop_tx(priv, tx, skb))) {
/* We need to ring the txq doorbell -- we have stopped the Tx
* queue for want of resources, but prior calls to gve_tx()
* may have added descriptors without ringing the doorbell.
@@ -672,19 +678,19 @@ static int gve_clean_tx_done(struct gve_priv *priv, struct gve_tx_ring *tx,
return pkts;
}
-__be32 gve_tx_load_event_counter(struct gve_priv *priv,
- struct gve_tx_ring *tx)
+u32 gve_tx_load_event_counter(struct gve_priv *priv,
+ struct gve_tx_ring *tx)
{
- u32 counter_index = be32_to_cpu((tx->q_resources->counter_index));
+ u32 counter_index = be32_to_cpu(tx->q_resources->counter_index);
+ __be32 counter = READ_ONCE(priv->counter_array[counter_index]);
- return READ_ONCE(priv->counter_array[counter_index]);
+ return be32_to_cpu(counter);
}
bool gve_tx_poll(struct gve_notify_block *block, int budget)
{
struct gve_priv *priv = block->priv;
struct gve_tx_ring *tx = block->tx;
- bool repoll = false;
u32 nic_done;
u32 to_do;
@@ -692,17 +698,23 @@ bool gve_tx_poll(struct gve_notify_block *block, int budget)
if (budget == 0)
budget = INT_MAX;
+ /* In TX path, it may try to clean completed pkts in order to xmit,
+ * to avoid cleaning conflict, use spin_lock(), it yields better
+ * concurrency between xmit/clean than netif's lock.
+ */
+ spin_lock(&tx->clean_lock);
/* Find out how much work there is to be done */
- tx->last_nic_done = gve_tx_load_event_counter(priv, tx);
- nic_done = be32_to_cpu(tx->last_nic_done);
- if (budget > 0) {
- /* Do as much work as we have that the budget will
- * allow
- */
- to_do = min_t(u32, (nic_done - tx->done), budget);
- gve_clean_tx_done(priv, tx, to_do, true);
- }
+ nic_done = gve_tx_load_event_counter(priv, tx);
+ to_do = min_t(u32, (nic_done - tx->done), budget);
+ gve_clean_tx_done(priv, tx, to_do, true);
+ spin_unlock(&tx->clean_lock);
/* If we still have work we want to repoll */
- repoll |= (nic_done != tx->done);
- return repoll;
+ return nic_done != tx->done;
+}
+
+bool gve_tx_clean_pending(struct gve_priv *priv, struct gve_tx_ring *tx)
+{
+ u32 nic_done = gve_tx_load_event_counter(priv, tx);
+
+ return nic_done != tx->done;
}
--
2.33.0.800.g4c38ced690-goog
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