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igbvf: refactor Interrupt Throttle Rate code
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The existing ITR code is broken and confusing, with lots of similarly-named
variables that do different things. Additionally, after the driver carefully
determines the optimal interrupt rate for the adapter, it then
ignores it and always writes a fixed, suboptimal value.

This patch refactors that code to make variable names more descriptive of
what they actually do, and then actually writes the calculated result to
the hardware.

Preliminary testing shows that netperf TCP_STREAM tests goes from ~918Mbps
to ~940Mbps, and TCP_RR goes from ~2k transactions/sec up to > 8k.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Robert E Garrett <robertX.e.garrett@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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Mitch A Williams authored and Jeff Kirsher committed Feb 7, 2012
1 parent 59d7402 commit ab50a2a
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Showing 3 changed files with 99 additions and 78 deletions.
19 changes: 10 additions & 9 deletions drivers/net/ethernet/intel/igbvf/ethtool.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -343,10 +343,10 @@ static int igbvf_get_coalesce(struct net_device *netdev,
{
struct igbvf_adapter *adapter = netdev_priv(netdev);

if (adapter->itr_setting <= 3)
ec->rx_coalesce_usecs = adapter->itr_setting;
if (adapter->requested_itr <= 3)
ec->rx_coalesce_usecs = adapter->requested_itr;
else
ec->rx_coalesce_usecs = adapter->itr_setting >> 2;
ec->rx_coalesce_usecs = adapter->current_itr >> 2;

return 0;
}
Expand All @@ -365,15 +365,16 @@ static int igbvf_set_coalesce(struct net_device *netdev,

/* convert to rate of irq's per second */
if (ec->rx_coalesce_usecs && ec->rx_coalesce_usecs <= 3) {
adapter->itr = IGBVF_START_ITR;
adapter->itr_setting = ec->rx_coalesce_usecs;
adapter->current_itr = IGBVF_START_ITR;
adapter->requested_itr = ec->rx_coalesce_usecs;
} else {
adapter->itr = ec->rx_coalesce_usecs << 2;
adapter->itr_setting = adapter->itr;
adapter->current_itr = ec->rx_coalesce_usecs << 2;
adapter->requested_itr = 1000000000 /
(adapter->current_itr * 256);
}

writel(adapter->itr,
hw->hw_addr + adapter->rx_ring[0].itr_register);
writel(adapter->current_itr,
hw->hw_addr + adapter->rx_ring->itr_register);

return 0;
}
Expand Down
27 changes: 15 additions & 12 deletions drivers/net/ethernet/intel/igbvf/igbvf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,18 @@ struct igbvf_info;
struct igbvf_adapter;

/* Interrupt defines */
#define IGBVF_START_ITR 648 /* ~6000 ints/sec */
#define IGBVF_START_ITR 488 /* ~8000 ints/sec */
#define IGBVF_4K_ITR 980
#define IGBVF_20K_ITR 196
#define IGBVF_70K_ITR 56

enum latency_range {
lowest_latency = 0,
low_latency = 1,
bulk_latency = 2,
latency_invalid = 255
};


/* Interrupt modes, as used by the IntMode parameter */
#define IGBVF_INT_MODE_LEGACY 0
Expand Down Expand Up @@ -155,6 +166,7 @@ struct igbvf_ring {
char name[IFNAMSIZ + 5];
u32 eims_value;
u32 itr_val;
enum latency_range itr_range;
u16 itr_register;
int set_itr;

Expand Down Expand Up @@ -187,10 +199,8 @@ struct igbvf_adapter {
unsigned long state;

/* Interrupt Throttle Rate */
u32 itr;
u32 itr_setting;
u16 tx_itr;
u16 rx_itr;
u32 requested_itr; /* ints/sec or adaptive */
u32 current_itr; /* Actual ITR register value, not ints/sec */

/*
* Tx
Expand Down Expand Up @@ -299,13 +309,6 @@ enum igbvf_state_t {
__IGBVF_DOWN
};

enum latency_range {
lowest_latency = 0,
low_latency = 1,
bulk_latency = 2,
latency_invalid = 255
};

extern char igbvf_driver_name[];
extern const char igbvf_driver_version[];

Expand Down
131 changes: 74 additions & 57 deletions drivers/net/ethernet/intel/igbvf/netdev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -632,14 +632,13 @@ void igbvf_free_rx_resources(struct igbvf_ring *rx_ring)
* traffic pattern. Constants in this function were computed
* based on theoretical maximum wire speed and thresholds were set based
* on testing data as well as attempting to minimize response time
* while increasing bulk throughput. This functionality is controlled
* by the InterruptThrottleRate module parameter.
* while increasing bulk throughput.
**/
static unsigned int igbvf_update_itr(struct igbvf_adapter *adapter,
u16 itr_setting, int packets,
int bytes)
static enum latency_range igbvf_update_itr(struct igbvf_adapter *adapter,
enum latency_range itr_setting,
int packets, int bytes)
{
unsigned int retval = itr_setting;
enum latency_range retval = itr_setting;

if (packets == 0)
goto update_itr_done;
Expand Down Expand Up @@ -675,65 +674,87 @@ static unsigned int igbvf_update_itr(struct igbvf_adapter *adapter,
retval = low_latency;
}
break;
default:
break;
}

update_itr_done:
return retval;
}

static void igbvf_set_itr(struct igbvf_adapter *adapter)
static int igbvf_range_to_itr(enum latency_range current_range)
{
struct e1000_hw *hw = &adapter->hw;
u16 current_itr;
u32 new_itr = adapter->itr;

adapter->tx_itr = igbvf_update_itr(adapter, adapter->tx_itr,
adapter->total_tx_packets,
adapter->total_tx_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;

adapter->rx_itr = igbvf_update_itr(adapter, adapter->rx_itr,
adapter->total_rx_packets,
adapter->total_rx_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;
int new_itr;

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

switch (current_itr) {
switch (current_range) {
/* counts and packets in update_itr are dependent on these numbers */
case lowest_latency:
new_itr = 70000;
new_itr = IGBVF_70K_ITR;
break;
case low_latency:
new_itr = 20000; /* aka hwitr = ~200 */
new_itr = IGBVF_20K_ITR;
break;
case bulk_latency:
new_itr = 4000;
new_itr = IGBVF_4K_ITR;
break;
default:
new_itr = IGBVF_START_ITR;
break;
}
return new_itr;
}

static void igbvf_set_itr(struct igbvf_adapter *adapter)
{
u32 new_itr;

adapter->tx_ring->itr_range =
igbvf_update_itr(adapter,
adapter->tx_ring->itr_val,
adapter->total_tx_packets,
adapter->total_tx_bytes);

/* conservative mode (itr 3) eliminates the lowest_latency setting */
if (adapter->requested_itr == 3 &&
adapter->tx_ring->itr_range == lowest_latency)
adapter->tx_ring->itr_range = low_latency;

if (new_itr != adapter->itr) {
new_itr = igbvf_range_to_itr(adapter->tx_ring->itr_range);


if (new_itr != adapter->tx_ring->itr_val) {
u32 current_itr = adapter->tx_ring->itr_val;
/*
* this attempts to bias the interrupt rate towards Bulk
* by adding intermediate steps when interrupt rate is
* increasing
*/
new_itr = new_itr > adapter->itr ?
min(adapter->itr + (new_itr >> 2), new_itr) :
new_itr;
adapter->itr = new_itr;
adapter->rx_ring->itr_val = 1952;

if (adapter->msix_entries)
adapter->rx_ring->set_itr = 1;
else
ew32(ITR, 1952);
new_itr = new_itr > current_itr ?
min(current_itr + (new_itr >> 2), new_itr) :
new_itr;
adapter->tx_ring->itr_val = new_itr;

adapter->tx_ring->set_itr = 1;
}

adapter->rx_ring->itr_range =
igbvf_update_itr(adapter, adapter->rx_ring->itr_val,
adapter->total_rx_packets,
adapter->total_rx_bytes);
if (adapter->requested_itr == 3 &&
adapter->rx_ring->itr_range == lowest_latency)
adapter->rx_ring->itr_range = low_latency;

new_itr = igbvf_range_to_itr(adapter->rx_ring->itr_range);

if (new_itr != adapter->rx_ring->itr_val) {
u32 current_itr = adapter->rx_ring->itr_val;
new_itr = new_itr > current_itr ?
min(current_itr + (new_itr >> 2), new_itr) :
new_itr;
adapter->rx_ring->itr_val = new_itr;

adapter->rx_ring->set_itr = 1;
}
}

Expand Down Expand Up @@ -835,6 +856,11 @@ static irqreturn_t igbvf_intr_msix_tx(int irq, void *data)
struct e1000_hw *hw = &adapter->hw;
struct igbvf_ring *tx_ring = adapter->tx_ring;

if (tx_ring->set_itr) {
writel(tx_ring->itr_val,
adapter->hw.hw_addr + tx_ring->itr_register);
adapter->tx_ring->set_itr = 0;
}

adapter->total_tx_bytes = 0;
adapter->total_tx_packets = 0;
Expand Down Expand Up @@ -937,19 +963,10 @@ static void igbvf_configure_msix(struct igbvf_adapter *adapter)

igbvf_assign_vector(adapter, IGBVF_NO_QUEUE, 0, vector++);
adapter->eims_enable_mask |= tx_ring->eims_value;
if (tx_ring->itr_val)
writel(tx_ring->itr_val,
hw->hw_addr + tx_ring->itr_register);
else
writel(1952, hw->hw_addr + tx_ring->itr_register);

writel(tx_ring->itr_val, hw->hw_addr + tx_ring->itr_register);
igbvf_assign_vector(adapter, 0, IGBVF_NO_QUEUE, vector++);
adapter->eims_enable_mask |= rx_ring->eims_value;
if (rx_ring->itr_val)
writel(rx_ring->itr_val,
hw->hw_addr + rx_ring->itr_register);
else
writel(1952, hw->hw_addr + rx_ring->itr_register);
writel(rx_ring->itr_val, hw->hw_addr + rx_ring->itr_register);

/* set vector for other causes, i.e. link changes */

Expand Down Expand Up @@ -1027,7 +1044,7 @@ static int igbvf_request_msix(struct igbvf_adapter *adapter)
goto out;

adapter->tx_ring->itr_register = E1000_EITR(vector);
adapter->tx_ring->itr_val = 1952;
adapter->tx_ring->itr_val = adapter->current_itr;
vector++;

err = request_irq(adapter->msix_entries[vector].vector,
Expand All @@ -1037,7 +1054,7 @@ static int igbvf_request_msix(struct igbvf_adapter *adapter)
goto out;

adapter->rx_ring->itr_register = E1000_EITR(vector);
adapter->rx_ring->itr_val = 1952;
adapter->rx_ring->itr_val = adapter->current_itr;
vector++;

err = request_irq(adapter->msix_entries[vector].vector,
Expand Down Expand Up @@ -1151,7 +1168,7 @@ static int igbvf_poll(struct napi_struct *napi, int budget)
if (work_done < budget) {
napi_complete(napi);

if (adapter->itr_setting & 3)
if (adapter->requested_itr & 3)
igbvf_set_itr(adapter);

if (!test_bit(__IGBVF_DOWN, &adapter->state))
Expand Down Expand Up @@ -1521,8 +1538,8 @@ static int __devinit igbvf_sw_init(struct igbvf_adapter *adapter)
adapter->tx_abs_int_delay = 32;
adapter->rx_int_delay = 0;
adapter->rx_abs_int_delay = 8;
adapter->itr_setting = 3;
adapter->itr = 20000;
adapter->requested_itr = 3;
adapter->current_itr = IGBVF_START_ITR;

/* Set various function pointers */
adapter->ei->init_ops(&adapter->hw);
Expand Down

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