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Subject[NET-NEXT PATCH 20/20] igb: Improve multiqueue AIM support
Date
From: Alexander Duyck <alexander.h.duyck@intel.com>

Improve multiqueue performance
Change itr_val to reflect ITR timer value instead of ints/sec
Cleaned up AIM algorithms in general

Based on work by Mitch Williams

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
---

drivers/net/igb/igb.h | 8 +-
drivers/net/igb/igb_ethtool.c | 17 +++-
drivers/net/igb/igb_main.c | 169 ++++++++++++++++++++++++-----------------
3 files changed, 113 insertions(+), 81 deletions(-)

diff --git a/drivers/net/igb/igb.h b/drivers/net/igb/igb.h
index c25ca17..56de7ec 100644
--- a/drivers/net/igb/igb.h
+++ b/drivers/net/igb/igb.h
@@ -47,7 +47,9 @@ struct igb_adapter;

#define IGB_MIN_DYN_ITR 3000
#define IGB_MAX_DYN_ITR 96000
-#define IGB_START_ITR 6000
+
+/* ((1000000000ns / (6000ints/s * 1024ns)) << 2 = 648 */
+#define IGB_START_ITR 648

#define IGB_DYN_ITR_PACKET_THRESHOLD 2
#define IGB_DYN_ITR_LENGTH_LOW 200
@@ -170,9 +172,10 @@ struct igb_ring {
};
/* RX */
struct {
- int no_itr_adjust;
struct igb_queue_stats rx_stats;
struct napi_struct napi;
+ int set_itr;
+ struct igb_ring *buddy;
#ifdef CONFIG_IGB_LRO
struct net_lro_mgr lro_mgr;
bool lro_used;
@@ -219,7 +222,6 @@ struct igb_adapter {
u32 itr_setting;
u16 tx_itr;
u16 rx_itr;
- int set_itr;

struct work_struct reset_task;
struct work_struct watchdog_task;
diff --git a/drivers/net/igb/igb_ethtool.c b/drivers/net/igb/igb_ethtool.c
index 7db1830..11aee13 100644
--- a/drivers/net/igb/igb_ethtool.c
+++ b/drivers/net/igb/igb_ethtool.c
@@ -1861,6 +1861,8 @@ static int igb_set_coalesce(struct net_device *netdev,
struct ethtool_coalesce *ec)
{
struct igb_adapter *adapter = netdev_priv(netdev);
+ struct e1000_hw *hw = &adapter->hw;
+ int i;

if ((ec->rx_coalesce_usecs > IGB_MAX_ITR_USECS) ||
((ec->rx_coalesce_usecs > 3) &&
@@ -1869,13 +1871,16 @@ static int igb_set_coalesce(struct net_device *netdev,
return -EINVAL;

/* convert to rate of irq's per second */
- if (ec->rx_coalesce_usecs <= 3)
+ if (ec->rx_coalesce_usecs && ec->rx_coalesce_usecs <= 3) {
adapter->itr_setting = ec->rx_coalesce_usecs;
- else
- adapter->itr_setting = (1000000 / ec->rx_coalesce_usecs);
+ adapter->itr = IGB_START_ITR;
+ } else {
+ adapter->itr_setting = ec->rx_coalesce_usecs << 2;
+ adapter->itr = adapter->itr_setting;
+ }

- if (netif_running(netdev))
- igb_reinit_locked(adapter);
+ for (i = 0; i < adapter->num_rx_queues; i++)
+ wr32(adapter->rx_ring[i].itr_register, adapter->itr);

return 0;
}
@@ -1888,7 +1893,7 @@ static int igb_get_coalesce(struct net_device *netdev,
if (adapter->itr_setting <= 3)
ec->rx_coalesce_usecs = adapter->itr_setting;
else
- ec->rx_coalesce_usecs = 1000000 / adapter->itr_setting;
+ ec->rx_coalesce_usecs = adapter->itr_setting >> 2;

return 0;
}
diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
index 2a5303c..aaed129 100644
--- a/drivers/net/igb/igb_main.c
+++ b/drivers/net/igb/igb_main.c
@@ -255,6 +255,8 @@ static int igb_alloc_queues(struct igb_adapter *adapter)
return -ENOMEM;
}

+ adapter->rx_ring->buddy = adapter->tx_ring;
+
for (i = 0; i < adapter->num_tx_queues; i++) {
struct igb_ring *ring = &(adapter->tx_ring[i]);
ring->adapter = adapter;
@@ -375,7 +377,7 @@ static void igb_configure_msix(struct igb_adapter *adapter)
igb_assign_vector(adapter, IGB_N0_QUEUE, i, vector++);
adapter->eims_enable_mask |= tx_ring->eims_value;
if (tx_ring->itr_val)
- writel(1000000000 / (tx_ring->itr_val * 256),
+ writel(tx_ring->itr_val,
hw->hw_addr + tx_ring->itr_register);
else
writel(1, hw->hw_addr + tx_ring->itr_register);
@@ -383,10 +385,11 @@ static void igb_configure_msix(struct igb_adapter *adapter)

for (i = 0; i < adapter->num_rx_queues; i++) {
struct igb_ring *rx_ring = &adapter->rx_ring[i];
+ rx_ring->buddy = 0;
igb_assign_vector(adapter, i, IGB_N0_QUEUE, vector++);
adapter->eims_enable_mask |= rx_ring->eims_value;
if (rx_ring->itr_val)
- writel(1000000000 / (rx_ring->itr_val * 256),
+ writel(rx_ring->itr_val,
hw->hw_addr + rx_ring->itr_register);
else
writel(1, hw->hw_addr + rx_ring->itr_register);
@@ -449,7 +452,7 @@ static int igb_request_msix(struct igb_adapter *adapter)
if (err)
goto out;
ring->itr_register = E1000_EITR(0) + (vector << 2);
- ring->itr_val = adapter->itr;
+ ring->itr_val = 976; /* ~4000 ints/sec */
vector++;
}
for (i = 0; i < adapter->num_rx_queues; i++) {
@@ -1898,8 +1901,7 @@ static void igb_configure_rx(struct igb_adapter *adapter)
mdelay(10);

if (adapter->itr_setting > 3)
- wr32(E1000_ITR,
- 1000000000 / (adapter->itr * 256));
+ wr32(E1000_ITR, adapter->itr);

/* Setup the HW Rx Head and Tail Descriptor Pointers and
* the Base and Length of the Rx Descriptor Ring */
@@ -2463,38 +2465,60 @@ enum latency_range {
};


-static void igb_lower_rx_eitr(struct igb_adapter *adapter,
- struct igb_ring *rx_ring)
+/**
+ * igb_update_ring_itr - update the dynamic ITR value based on packet size
+ *
+ * Stores a new ITR value based on strictly on packet size. This
+ * algorithm is less sophisticated than that used in igb_update_itr,
+ * due to the difficulty of synchronizing statistics across multiple
+ * receive rings. The divisors and thresholds used by this fuction
+ * were determined based on theoretical maximum wire speed and testing
+ * data, in order to minimize response time while increasing bulk
+ * throughput.
+ * This functionality is controlled by the InterruptThrottleRate module
+ * parameter (see igb_param.c)
+ * NOTE: This function is called only when operating in a multiqueue
+ * receive environment.
+ * @rx_ring: pointer to ring
+ **/
+static void igb_update_ring_itr(struct igb_ring *rx_ring)
{
- struct e1000_hw *hw = &adapter->hw;
- int new_val;
+ int new_val = rx_ring->itr_val;
+ int avg_wire_size = 0;
+ struct igb_adapter *adapter = rx_ring->adapter;

- new_val = rx_ring->itr_val / 2;
- if (new_val < IGB_MIN_DYN_ITR)
- new_val = IGB_MIN_DYN_ITR;
+ if (!rx_ring->total_packets)
+ goto clear_counts; /* no packets, so don't do anything */

- if (new_val != rx_ring->itr_val) {
- rx_ring->itr_val = new_val;
- wr32(rx_ring->itr_register,
- 1000000000 / (new_val * 256));
+ /* For non-gigabit speeds, just fix the interrupt rate at 4000
+ * ints/sec - ITR timer value of 120 ticks.
+ */
+ if (adapter->link_speed != SPEED_1000) {
+ new_val = 120;
+ goto set_itr_val;
}
-}
+ avg_wire_size = rx_ring->total_bytes / rx_ring->total_packets;

-static void igb_raise_rx_eitr(struct igb_adapter *adapter,
- struct igb_ring *rx_ring)
-{
- struct e1000_hw *hw = &adapter->hw;
- int new_val;
+ /* Add 24 bytes to size to account for CRC, preamble, and gap */
+ avg_wire_size += 24;
+
+ /* Don't starve jumbo frames */
+ avg_wire_size = min(avg_wire_size, 3000);

- new_val = rx_ring->itr_val * 2;
- if (new_val > IGB_MAX_DYN_ITR)
- new_val = IGB_MAX_DYN_ITR;
+ /* Give a little boost to mid-size frames */
+ if ((avg_wire_size > 300) && (avg_wire_size < 1200))
+ new_val = avg_wire_size / 3;
+ else
+ new_val = avg_wire_size / 2;

+set_itr_val:
if (new_val != rx_ring->itr_val) {
rx_ring->itr_val = new_val;
- wr32(rx_ring->itr_register,
- 1000000000 / (new_val * 256));
+ rx_ring->set_itr = 1;
}
+clear_counts:
+ rx_ring->total_bytes = 0;
+ rx_ring->total_packets = 0;
}

/**
@@ -2561,8 +2585,7 @@ update_itr_done:
return retval;
}

-static void igb_set_itr(struct igb_adapter *adapter, u16 itr_register,
- int rx_only)
+static void igb_set_itr(struct igb_adapter *adapter)
{
u16 current_itr;
u32 new_itr = adapter->itr;
@@ -2578,26 +2601,23 @@ static void igb_set_itr(struct igb_adapter *adapter, u16 itr_register,
adapter->rx_itr,
adapter->rx_ring->total_packets,
adapter->rx_ring->total_bytes);
- /* conservative mode (itr 3) eliminates the lowest_latency setting */
- if (adapter->itr_setting == 3 && adapter->rx_itr == lowest_latency)
- adapter->rx_itr = low_latency;

- if (!rx_only) {
+ if (adapter->rx_ring->buddy) {
adapter->tx_itr = igb_update_itr(adapter,
adapter->tx_itr,
adapter->tx_ring->total_packets,
adapter->tx_ring->total_bytes);
- /* conservative mode (itr 3) eliminates the
- * lowest_latency setting */
- if (adapter->itr_setting == 3 &&
- adapter->tx_itr == lowest_latency)
- adapter->tx_itr = low_latency;

current_itr = max(adapter->rx_itr, adapter->tx_itr);
} else {
current_itr = adapter->rx_itr;
}

+ /* conservative mode (itr 3) eliminates the lowest_latency setting */
+ if (adapter->itr_setting == 3 &&
+ current_itr == lowest_latency)
+ current_itr = low_latency;
+
switch (current_itr) {
/* counts and packets in update_itr are dependent on these numbers */
case lowest_latency:
@@ -2614,6 +2634,13 @@ static void igb_set_itr(struct igb_adapter *adapter, u16 itr_register,
}

set_itr_now:
+ adapter->rx_ring->total_bytes = 0;
+ adapter->rx_ring->total_packets = 0;
+ if (adapter->rx_ring->buddy) {
+ adapter->rx_ring->buddy->total_bytes = 0;
+ adapter->rx_ring->buddy->total_packets = 0;
+ }
+
if (new_itr != adapter->itr) {
/* this attempts to bias the interrupt rate towards Bulk
* by adding intermediate steps when interrupt rate is
@@ -2628,7 +2655,8 @@ set_itr_now:
* ends up being correct.
*/
adapter->itr = new_itr;
- adapter->set_itr = 1;
+ adapter->rx_ring->itr_val = 1000000000 / (new_itr * 256);
+ adapter->rx_ring->set_itr = 1;
}

return;
@@ -2979,6 +3007,7 @@ static int igb_xmit_frame_ring_adv(struct sk_buff *skb,
/* this is a hard error */
return NETDEV_TX_BUSY;
}
+ skb_orphan(skb);

if (adapter->vlgrp && vlan_tx_tag_present(skb)) {
tx_flags |= IGB_TX_FLAGS_VLAN;
@@ -3312,8 +3341,6 @@ static irqreturn_t igb_msix_tx(int irq, void *data)
struct igb_adapter *adapter = tx_ring->adapter;
struct e1000_hw *hw = &adapter->hw;

- if (!tx_ring->itr_val)
- wr32(E1000_EIMC, tx_ring->eims_value);
#ifdef CONFIG_DCA
if (adapter->flags & IGB_FLAG_DCA_ENABLED)
igb_update_tx_dca(tx_ring);
@@ -3332,21 +3359,36 @@ static irqreturn_t igb_msix_tx(int irq, void *data)
return IRQ_HANDLED;
}

+static void igb_write_itr(struct igb_ring *ring)
+{
+ struct e1000_hw *hw = &ring->adapter->hw;
+ if ((ring->adapter->itr_setting & 3) && ring->set_itr) {
+ switch (hw->mac.type) {
+ case e1000_82576:
+ wr32(ring->itr_register,
+ ring->itr_val |
+ 0x80000000);
+ break;
+ default:
+ wr32(ring->itr_register,
+ ring->itr_val |
+ (ring->itr_val << 16));
+ break;
+ }
+ ring->set_itr = 0;
+ }
+}
+
static irqreturn_t igb_msix_rx(int irq, void *data)
{
struct igb_ring *rx_ring = data;
struct igb_adapter *adapter = rx_ring->adapter;
- struct e1000_hw *hw = &adapter->hw;

/* Write the ITR value calculated at the end of the
* previous interrupt.
*/

- if (adapter->set_itr) {
- wr32(rx_ring->itr_register,
- 1000000000 / (rx_ring->itr_val * 256));
- adapter->set_itr = 0;
- }
+ igb_write_itr(rx_ring);

if (netif_rx_schedule_prep(adapter->netdev, &rx_ring->napi))
__netif_rx_schedule(adapter->netdev, &rx_ring->napi);
@@ -3493,13 +3535,7 @@ static irqreturn_t igb_intr_msi(int irq, void *data)
/* read ICR disables interrupts using IAM */
u32 icr = rd32(E1000_ICR);

- /* Write the ITR value calculated at the end of the
- * previous interrupt.
- */
- if (adapter->set_itr) {
- wr32(E1000_ITR, 1000000000 / (adapter->itr * 256));
- adapter->set_itr = 0;
- }
+ igb_write_itr(adapter->rx_ring);

if (icr & (E1000_ICR_RXSEQ | E1000_ICR_LSC)) {
hw->mac.get_link_status = 1;
@@ -3529,13 +3565,7 @@ static irqreturn_t igb_intr(int irq, void *data)
if (!icr)
return IRQ_NONE; /* Not our interrupt */

- /* Write the ITR value calculated at the end of the
- * previous interrupt.
- */
- if (adapter->set_itr) {
- wr32(E1000_ITR, 1000000000 / (adapter->itr * 256));
- adapter->set_itr = 0;
- }
+ igb_write_itr(adapter->rx_ring);

/* IMS will not auto-mask if INT_ASSERTED is not set, and if it is
* not set, then the adapter didn't send an interrupt */
@@ -3585,7 +3615,7 @@ static int igb_poll(struct napi_struct *napi, int budget)
if ((tx_clean_complete && (work_done < budget)) ||
!netif_running(netdev)) {
if (adapter->itr_setting & 3)
- igb_set_itr(adapter, E1000_ITR, false);
+ igb_set_itr(adapter);
netif_rx_complete(netdev, napi);
if (!test_bit(__IGB_DOWN, &adapter->state))
igb_irq_enable(adapter);
@@ -3619,15 +3649,11 @@ static int igb_clean_rx_ring_msix(struct napi_struct *napi, int budget)
quit_polling:
netif_rx_complete(netdev, napi);

- wr32(E1000_EIMS, rx_ring->eims_value);
- if ((adapter->itr_setting & 3) && !rx_ring->no_itr_adjust &&
- (rx_ring->total_packets > IGB_DYN_ITR_PACKET_THRESHOLD)) {
- int mean_size = rx_ring->total_bytes /
- rx_ring->total_packets;
- if (mean_size < IGB_DYN_ITR_LENGTH_LOW)
- igb_raise_rx_eitr(adapter, rx_ring);
- else if (mean_size > IGB_DYN_ITR_LENGTH_HIGH)
- igb_lower_rx_eitr(adapter, rx_ring);
+ if (adapter->itr_setting & 3) {
+ if (adapter->num_rx_queues == 1)
+ igb_set_itr(adapter);
+ else
+ igb_update_ring_itr(rx_ring);
}

if (!test_bit(__IGB_DOWN, &adapter->state))
@@ -3972,7 +3998,6 @@ send_up:
dev_kfree_skb_irq(skb);
goto next_desc;
}
- rx_ring->no_itr_adjust |= (staterr & E1000_RXD_STAT_DYNINT);

total_bytes += skb->len;
total_packets++;


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