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ixgbe: Cleanup q_vector interrupt throttle rate logic
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This patch is meant to help cleanup the interrupt throttle rate logic by
storing the interrupt throttle rate as a value in microseconds instead of
interrupts per second.  The advantage to this approach is that the value
can now be stored in an 16 bit field and doesn't require as much math to
flip the value back and forth since the hardware already used microseconds
when setting the rate.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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Emil Tantilov authored and Jeff Kirsher committed Sep 29, 2011
1 parent dd1ed3b commit d5bf4f6
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Showing 3 changed files with 96 additions and 159 deletions.
25 changes: 14 additions & 11 deletions drivers/net/ethernet/intel/ixgbe/ixgbe.h
Original file line number Diff line number Diff line change
Expand Up @@ -301,26 +301,29 @@ struct ixgbe_ring_container {
*/
struct ixgbe_q_vector {
struct ixgbe_adapter *adapter;
unsigned int v_idx; /* index of q_vector within array, also used for
* finding the bit in EICR and friends that
* represents the vector for this ring */
#ifdef CONFIG_IXGBE_DCA
int cpu; /* CPU for DCA */
#endif
struct napi_struct napi;
u16 v_idx; /* index of q_vector within array, also used for
* finding the bit in EICR and friends that
* represents the vector for this ring */
u16 itr; /* Interrupt throttle rate written to EITR */
struct ixgbe_ring_container rx, tx;
u32 eitr;

struct napi_struct napi;
cpumask_var_t affinity_mask;
char name[IFNAMSIZ + 9];
};

/* Helper macros to switch between ints/sec and what the register uses.
* And yes, it's the same math going both ways. The lowest value
* supported by all of the ixgbe hardware is 8.
/*
* microsecond values for various ITR rates shifted by 2 to fit itr register
* with the first 3 bits reserved 0
*/
#define EITR_INTS_PER_SEC_TO_REG(_eitr) \
((_eitr) ? (1000000000 / ((_eitr) * 256)) : 8)
#define EITR_REG_TO_INTS_PER_SEC EITR_INTS_PER_SEC_TO_REG
#define IXGBE_MIN_RSC_ITR 24
#define IXGBE_100K_ITR 40
#define IXGBE_20K_ITR 200
#define IXGBE_10K_ITR 400
#define IXGBE_8K_ITR 500

static inline u16 ixgbe_desc_unused(struct ixgbe_ring *ring)
{
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153 changes: 47 additions & 106 deletions drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
Original file line number Diff line number Diff line change
Expand Up @@ -2026,39 +2026,20 @@ static int ixgbe_get_coalesce(struct net_device *netdev,
ec->tx_max_coalesced_frames_irq = adapter->tx_work_limit;

/* only valid if in constant ITR mode */
switch (adapter->rx_itr_setting) {
case 0:
/* throttling disabled */
ec->rx_coalesce_usecs = 0;
break;
case 1:
/* dynamic ITR mode */
ec->rx_coalesce_usecs = 1;
break;
default:
/* fixed interrupt rate mode */
ec->rx_coalesce_usecs = 1000000/adapter->rx_eitr_param;
break;
}
if (adapter->rx_itr_setting <= 1)
ec->rx_coalesce_usecs = adapter->rx_itr_setting;
else
ec->rx_coalesce_usecs = adapter->rx_itr_setting >> 2;

/* if in mixed tx/rx queues per vector mode, report only rx settings */
if (adapter->q_vector[0]->tx.count && adapter->q_vector[0]->rx.count)
return 0;

/* only valid if in constant ITR mode */
switch (adapter->tx_itr_setting) {
case 0:
/* throttling disabled */
ec->tx_coalesce_usecs = 0;
break;
case 1:
/* dynamic ITR mode */
ec->tx_coalesce_usecs = 1;
break;
default:
ec->tx_coalesce_usecs = 1000000/adapter->tx_eitr_param;
break;
}
if (adapter->tx_itr_setting <= 1)
ec->tx_coalesce_usecs = adapter->tx_itr_setting;
else
ec->tx_coalesce_usecs = adapter->tx_itr_setting >> 2;

return 0;
}
Expand All @@ -2077,19 +2058,17 @@ static bool ixgbe_update_rsc(struct ixgbe_adapter *adapter,

/* if interrupt rate is too high then disable RSC */
if (ec->rx_coalesce_usecs != 1 &&
ec->rx_coalesce_usecs <= 1000000/IXGBE_MAX_RSC_INT_RATE) {
ec->rx_coalesce_usecs <= (IXGBE_MIN_RSC_ITR >> 2)) {
if (adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED) {
e_info(probe, "rx-usecs set too low, "
"disabling RSC\n");
e_info(probe, "rx-usecs set too low, disabling RSC\n");
adapter->flags2 &= ~IXGBE_FLAG2_RSC_ENABLED;
return true;
}
} else {
/* check the feature flag value and enable RSC if necessary */
if ((netdev->features & NETIF_F_LRO) &&
!(adapter->flags2 & IXGBE_FLAG2_RSC_ENABLED)) {
e_info(probe, "rx-usecs set to %d, "
"re-enabling RSC\n",
e_info(probe, "rx-usecs set to %d, re-enabling RSC\n",
ec->rx_coalesce_usecs);
adapter->flags2 |= IXGBE_FLAG2_RSC_ENABLED;
return true;
Expand All @@ -2104,97 +2083,59 @@ static int ixgbe_set_coalesce(struct net_device *netdev,
struct ixgbe_adapter *adapter = netdev_priv(netdev);
struct ixgbe_q_vector *q_vector;
int i;
int num_vectors;
u16 tx_itr_param, rx_itr_param;
bool need_reset = false;

/* don't accept tx specific changes if we've got mixed RxTx vectors */
if (adapter->q_vector[0]->tx.count && adapter->q_vector[0]->rx.count
&& ec->tx_coalesce_usecs)
&& ec->tx_coalesce_usecs)
return -EINVAL;

if (ec->tx_max_coalesced_frames_irq)
adapter->tx_work_limit = ec->tx_max_coalesced_frames_irq;

if (ec->rx_coalesce_usecs > 1) {
/* check the limits */
if ((1000000/ec->rx_coalesce_usecs > IXGBE_MAX_INT_RATE) ||
(1000000/ec->rx_coalesce_usecs < IXGBE_MIN_INT_RATE))
return -EINVAL;

/* check the old value and enable RSC if necessary */
need_reset = ixgbe_update_rsc(adapter, ec);

/* store the value in ints/second */
adapter->rx_eitr_param = 1000000/ec->rx_coalesce_usecs;
if ((ec->rx_coalesce_usecs > (IXGBE_MAX_EITR >> 2)) ||
(ec->tx_coalesce_usecs > (IXGBE_MAX_EITR >> 2)))
return -EINVAL;

/* static value of interrupt rate */
adapter->rx_itr_setting = adapter->rx_eitr_param;
/* clear the lower bit as its used for dynamic state */
adapter->rx_itr_setting &= ~1;
} else if (ec->rx_coalesce_usecs == 1) {
/* check the old value and enable RSC if necessary */
need_reset = ixgbe_update_rsc(adapter, ec);
/* check the old value and enable RSC if necessary */
need_reset = ixgbe_update_rsc(adapter, ec);

/* 1 means dynamic mode */
adapter->rx_eitr_param = 20000;
adapter->rx_itr_setting = 1;
} else {
/* check the old value and enable RSC if necessary */
need_reset = ixgbe_update_rsc(adapter, ec);
/*
* any other value means disable eitr, which is best
* served by setting the interrupt rate very high
*/
adapter->rx_eitr_param = IXGBE_MAX_INT_RATE;
adapter->rx_itr_setting = 0;
}
if (ec->rx_coalesce_usecs > 1)
adapter->rx_itr_setting = ec->rx_coalesce_usecs << 2;
else
adapter->rx_itr_setting = ec->rx_coalesce_usecs;

if (ec->tx_coalesce_usecs > 1) {
/*
* don't have to worry about max_int as above because
* tx vectors don't do hardware RSC (an rx function)
*/
/* check the limits */
if ((1000000/ec->tx_coalesce_usecs > IXGBE_MAX_INT_RATE) ||
(1000000/ec->tx_coalesce_usecs < IXGBE_MIN_INT_RATE))
return -EINVAL;
if (adapter->rx_itr_setting == 1)
rx_itr_param = IXGBE_20K_ITR;
else
rx_itr_param = adapter->rx_itr_setting;

/* store the value in ints/second */
adapter->tx_eitr_param = 1000000/ec->tx_coalesce_usecs;
if (ec->tx_coalesce_usecs > 1)
adapter->tx_itr_setting = ec->tx_coalesce_usecs << 2;
else
adapter->tx_itr_setting = ec->tx_coalesce_usecs;

/* static value of interrupt rate */
adapter->tx_itr_setting = adapter->tx_eitr_param;
if (adapter->tx_itr_setting == 1)
tx_itr_param = IXGBE_10K_ITR;
else
tx_itr_param = adapter->tx_itr_setting;

/* clear the lower bit as its used for dynamic state */
adapter->tx_itr_setting &= ~1;
} else if (ec->tx_coalesce_usecs == 1) {
/* 1 means dynamic mode */
adapter->tx_eitr_param = 10000;
adapter->tx_itr_setting = 1;
} else {
adapter->tx_eitr_param = IXGBE_MAX_INT_RATE;
adapter->tx_itr_setting = 0;
}
if (adapter->flags & IXGBE_FLAG_MSIX_ENABLED)
num_vectors = adapter->num_msix_vectors - NON_Q_VECTORS;
else
num_vectors = 1;

/* MSI/MSIx Interrupt Mode */
if (adapter->flags &
(IXGBE_FLAG_MSIX_ENABLED | IXGBE_FLAG_MSI_ENABLED)) {
int num_vectors = adapter->num_msix_vectors - NON_Q_VECTORS;
for (i = 0; i < num_vectors; i++) {
q_vector = adapter->q_vector[i];
if (q_vector->tx.count && !q_vector->rx.count)
/* tx only */
q_vector->eitr = adapter->tx_eitr_param;
else
/* rx only or mixed */
q_vector->eitr = adapter->rx_eitr_param;
q_vector->tx.work_limit = adapter->tx_work_limit;
ixgbe_write_eitr(q_vector);
}
/* Legacy Interrupt Mode */
} else {
q_vector = adapter->q_vector[0];
q_vector->eitr = adapter->rx_eitr_param;
for (i = 0; i < num_vectors; i++) {
q_vector = adapter->q_vector[i];
q_vector->tx.work_limit = adapter->tx_work_limit;
if (q_vector->tx.count && !q_vector->rx.count)
/* tx only */
q_vector->itr = tx_itr_param;
else
/* rx only or mixed */
q_vector->itr = rx_itr_param;
ixgbe_write_eitr(q_vector);
}

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