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ice: Calculate ITR increment based on direct calculation 

Currently when calculating how much to increment ITR by inside of
ice_update_itr() we do some estimations and intermediate
calculations. Instead of doing estimations, just do the
calculation directly. This allows for a more accurate value and it
makes it easier for the next person to understand and update.

Also, remove the dividing the ITR value by 2 when latency
driven because the ITR values are already so low for 100Gbps
speed. This should help get to the desired ITR value faster.

Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Brett Creeley 2019-02-28 15:25:47 -08:00 committed by Jeff Kirsher
parent 9c010de7cf
commit 711987bbad
1 changed files with 63 additions and 72 deletions
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135
drivers/net/ethernet/intel/ice/ice_txrx.c
View File

@ -1097,19 +1097,69 @@ static int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget)
return failure ? budget : (int)total_rx_pkts;
}
static unsigned int ice_itr_divisor(struct ice_port_info *pi)
/**
* ice_adjust_itr_by_size_and_speed - Adjust ITR based on current traffic
* @port_info: port_info structure containing the current link speed
* @avg_pkt_size: average size of Tx or Rx packets based on clean routine
* @itr: itr value to update
*
* Calculate how big of an increment should be applied to the ITR value passed
* in based on wmem_default, SKB overhead, Ethernet overhead, and the current
* link speed.
*
* The following is a calculation derived from:
* wmem_default / (size + overhead) = desired_pkts_per_int
* rate / bits_per_byte / (size + Ethernet overhead) = pkt_rate
* (desired_pkt_rate / pkt_rate) * usecs_per_sec = ITR value
*
* Assuming wmem_default is 212992 and overhead is 640 bytes per
* packet, (256 skb, 64 headroom, 320 shared info), we can reduce the
* formula down to:
*
* wmem_default * bits_per_byte * usecs_per_sec pkt_size + 24
* ITR = -------------------------------------------- * --------------
* rate pkt_size + 640
*/
static unsigned int
ice_adjust_itr_by_size_and_speed(struct ice_port_info *port_info,
unsigned int avg_pkt_size,
unsigned int itr)
{
switch (pi->phy.link_info.link_speed) {
switch (port_info->phy.link_info.link_speed) {
case ICE_AQ_LINK_SPEED_100GB:
itr += DIV_ROUND_UP(17 * (avg_pkt_size + 24),
avg_pkt_size + 640);
break;
case ICE_AQ_LINK_SPEED_50GB:
itr += DIV_ROUND_UP(34 * (avg_pkt_size + 24),
avg_pkt_size + 640);
break;
case ICE_AQ_LINK_SPEED_40GB:
return ICE_ITR_ADAPTIVE_MIN_INC * 1024;
itr += DIV_ROUND_UP(43 * (avg_pkt_size + 24),
avg_pkt_size + 640);
break;
case ICE_AQ_LINK_SPEED_25GB:
itr += DIV_ROUND_UP(68 * (avg_pkt_size + 24),
avg_pkt_size + 640);
break;
case ICE_AQ_LINK_SPEED_20GB:
return ICE_ITR_ADAPTIVE_MIN_INC * 512;
case ICE_AQ_LINK_SPEED_100MB:
return ICE_ITR_ADAPTIVE_MIN_INC * 32;
itr += DIV_ROUND_UP(85 * (avg_pkt_size + 24),
avg_pkt_size + 640);
break;
case ICE_AQ_LINK_SPEED_10GB:
/* fall through */
default:
return ICE_ITR_ADAPTIVE_MIN_INC * 256;
itr += DIV_ROUND_UP(170 * (avg_pkt_size + 24),
avg_pkt_size + 640);
break;
}
if ((itr & ICE_ITR_MASK) > ICE_ITR_ADAPTIVE_MAX_USECS) {
itr &= ICE_ITR_ADAPTIVE_LATENCY;
itr += ICE_ITR_ADAPTIVE_MAX_USECS;
}
return itr;
}
/**
@ -1128,8 +1178,8 @@ static unsigned int ice_itr_divisor(struct ice_port_info *pi)
static void
ice_update_itr(struct ice_q_vector *q_vector, struct ice_ring_container *rc)
{
unsigned int avg_wire_size, packets, bytes, itr;
unsigned long next_update = jiffies;
unsigned int packets, bytes, itr;
bool container_is_rx;
if (!rc->ring || !ITR_IS_DYNAMIC(rc->itr_setting))
@ -1174,7 +1224,7 @@ ice_update_itr(struct ice_q_vector *q_vector, struct ice_ring_container *rc)
if (packets && packets < 4 && bytes < 9000 &&
(q_vector->tx.target_itr & ICE_ITR_ADAPTIVE_LATENCY)) {
itr = ICE_ITR_ADAPTIVE_LATENCY;
goto adjust_by_size;
goto adjust_by_size_and_speed;
}
} else if (packets < 4) {
/* If we have Tx and Rx ITR maxed and Tx ITR is running in
@ -1242,70 +1292,11 @@ ice_update_itr(struct ice_q_vector *q_vector, struct ice_ring_container *rc)
*/
itr = ICE_ITR_ADAPTIVE_BULK;
adjust_by_size:
/* If packet counts are 256 or greater we can assume we have a gross
* overestimation of what the rate should be. Instead of trying to fine
* tune it just use the formula below to try and dial in an exact value
* gives the current packet size of the frame.
*/
avg_wire_size = bytes / packets;
adjust_by_size_and_speed:
/* The following is a crude approximation of:
* wmem_default / (size + overhead) = desired_pkts_per_int
* rate / bits_per_byte / (size + ethernet overhead) = pkt_rate
* (desired_pkt_rate / pkt_rate) * usecs_per_sec = ITR value
*
* Assuming wmem_default is 212992 and overhead is 640 bytes per
* packet, (256 skb, 64 headroom, 320 shared info), we can reduce the
* formula down to
*
* (170 * (size + 24)) / (size + 640) = ITR
*
* We first do some math on the packet size and then finally bitshift
* by 8 after rounding up. We also have to account for PCIe link speed
* difference as ITR scales based on this.
*/
if (avg_wire_size <= 60) {
/* Start at 250k ints/sec */
avg_wire_size = 4096;
} else if (avg_wire_size <= 380) {
/* 250K ints/sec to 60K ints/sec */
avg_wire_size *= 40;
avg_wire_size += 1696;
} else if (avg_wire_size <= 1084) {
/* 60K ints/sec to 36K ints/sec */
avg_wire_size *= 15;
avg_wire_size += 11452;
} else if (avg_wire_size <= 1980) {
/* 36K ints/sec to 30K ints/sec */
avg_wire_size *= 5;
avg_wire_size += 22420;
} else {
/* plateau at a limit of 30K ints/sec */
avg_wire_size = 32256;
}
/* If we are in low latency mode halve our delay which doubles the
* rate to somewhere between 100K to 16K ints/sec
*/
if (itr & ICE_ITR_ADAPTIVE_LATENCY)
avg_wire_size >>= 1;
/* Resultant value is 256 times larger than it needs to be. This
* gives us room to adjust the value as needed to either increase
* or decrease the value based on link speeds of 10G, 2.5G, 1G, etc.
*
* Use addition as we have already recorded the new latency flag
* for the ITR value.
*/
itr += DIV_ROUND_UP(avg_wire_size,
ice_itr_divisor(q_vector->vsi->port_info)) *
ICE_ITR_ADAPTIVE_MIN_INC;
if ((itr & ICE_ITR_MASK) > ICE_ITR_ADAPTIVE_MAX_USECS) {
itr &= ICE_ITR_ADAPTIVE_LATENCY;
itr += ICE_ITR_ADAPTIVE_MAX_USECS;
}
/* based on checks above packets cannot be 0 so division is safe */
itr = ice_adjust_itr_by_size_and_speed(q_vector->vsi->port_info,
bytes / packets, itr);
clear_counts:
/* write back value */