static void ixgbe_update_itr(struct ixgbe_q_vector *q_vector,
struct ixgbe_ring_container *ring_container)
{
- int bytes = ring_container->total_bytes;
- int packets = ring_container->total_packets;
- u32 timepassed_us;
- u64 bytes_perint;
- u8 itr_setting = ring_container->itr;
+ unsigned int itr = IXGBE_ITR_ADAPTIVE_MIN_USECS |
+ IXGBE_ITR_ADAPTIVE_LATENCY;
+ unsigned int avg_wire_size, packets, bytes;
+ unsigned long next_update = jiffies;
- if (packets == 0)
+ /* If we don't have any rings just leave ourselves set for maximum
+ * possible latency so we take ourselves out of the equation.
+ */
+ if (!ring_container->ring)
return;
- /* simple throttlerate management
- * 0-10MB/s lowest (100000 ints/s)
- * 10-20MB/s low (20000 ints/s)
- * 20-1249MB/s bulk (12000 ints/s)
+ /* If we didn't update within up to 1 - 2 jiffies we can assume
+ * that either packets are coming in so slow there hasn't been
+ * any work, or that there is so much work that NAPI is dealing
+ * with interrupt moderation and we don't need to do anything.
*/
- /* what was last interrupt timeslice? */
- timepassed_us = q_vector->itr >> 2;
- if (timepassed_us == 0)
- return;
+ if (time_after(next_update, ring_container->next_update))
+ goto clear_counts;
- bytes_perint = bytes / timepassed_us; /* bytes/usec */
+ packets = ring_container->total_packets;
- switch (itr_setting) {
- case lowest_latency:
- if (bytes_perint > 10)
- itr_setting = low_latency;
- break;
- case low_latency:
- if (bytes_perint > 20)
- itr_setting = bulk_latency;
- else if (bytes_perint <= 10)
- itr_setting = lowest_latency;
+ /* We have no packets to actually measure against. This means
+ * either one of the other queues on this vector is active or
+ * we are a Tx queue doing TSO with too high of an interrupt rate.
+ *
+ * When this occurs just tick up our delay by the minimum value
+ * and hope that this extra delay will prevent us from being called
+ * without any work on our queue.
+ */
+ if (!packets) {
+ itr = (q_vector->itr >> 2) + IXGBE_ITR_ADAPTIVE_MIN_INC;
+ if (itr > IXGBE_ITR_ADAPTIVE_MAX_USECS)
+ itr = IXGBE_ITR_ADAPTIVE_MAX_USECS;
+ itr += ring_container->itr & IXGBE_ITR_ADAPTIVE_LATENCY;
+ goto clear_counts;
+ }
+
+ bytes = ring_container->total_bytes;
+
+ /* If packets are less than 4 or bytes are less than 9000 assume
+ * insufficient data to use bulk rate limiting approach. We are
+ * likely latency driven.
+ */
+ if (packets < 4 && bytes < 9000) {
+ itr = IXGBE_ITR_ADAPTIVE_LATENCY;
+ goto adjust_by_size;
+ }
+
+ /* Between 4 and 48 we can assume that our current interrupt delay
+ * is only slightly too low. As such we should increase it by a small
+ * fixed amount.
+ */
+ if (packets < 48) {
+ itr = (q_vector->itr >> 2) + IXGBE_ITR_ADAPTIVE_MIN_INC;
+ if (itr > IXGBE_ITR_ADAPTIVE_MAX_USECS)
+ itr = IXGBE_ITR_ADAPTIVE_MAX_USECS;
+ goto clear_counts;
+ }
+
+ /* Between 48 and 96 is our "goldilocks" zone where we are working
+ * out "just right". Just report that our current ITR is good for us.
+ */
+ if (packets < 96) {
+ itr = q_vector->itr >> 2;
+ goto clear_counts;
+ }
+
+ /* If packet count is 96 or greater we are likely looking at a slight
+ * overrun of the delay we want. Try halving our delay to see if that
+ * will cut the number of packets in half per interrupt.
+ */
+ if (packets < 256) {
+ itr = q_vector->itr >> 3;
+ if (itr < IXGBE_ITR_ADAPTIVE_MIN_USECS)
+ itr = IXGBE_ITR_ADAPTIVE_MIN_USECS;
+ goto clear_counts;
+ }
+
+ /* The paths below assume we are dealing with a bulk ITR since number
+ * of packets is 256 or greater. We are just going to have to compute
+ * a value and try to bring the count under control, though for smaller
+ * packet sizes there isn't much we can do as NAPI polling will likely
+ * be kicking in sooner rather than later.
+ */
+ itr = IXGBE_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
+ * give the current packet size of the frame.
+ */
+ avg_wire_size = bytes / packets;
+
+ /* 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 50k ints/sec */
+ avg_wire_size = 5120;
+ } else if (avg_wire_size <= 316) {
+ /* 50K ints/sec to 16K ints/sec */
+ avg_wire_size *= 40;
+ avg_wire_size += 2720;
+ } else if (avg_wire_size <= 1084) {
+ /* 16K ints/sec to 9.2K ints/sec */
+ avg_wire_size *= 15;
+ avg_wire_size += 11452;
+ } else if (avg_wire_size <= 1980) {
+ /* 9.2K ints/sec to 8K ints/sec */
+ avg_wire_size *= 5;
+ avg_wire_size += 22420;
+ } else {
+ /* plateau at a limit of 8K ints/sec */
+ avg_wire_size = 32256;
+ }
+
+ /* If we are in low latency mode half our delay which doubles the rate
+ * to somewhere between 100K to 16K ints/sec
+ */
+ if (itr & IXGBE_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.
+ */
+ switch (q_vector->adapter->link_speed) {
+ case IXGBE_LINK_SPEED_10GB_FULL:
+ case IXGBE_LINK_SPEED_100_FULL:
+ default:
+ itr += DIV_ROUND_UP(avg_wire_size,
+ IXGBE_ITR_ADAPTIVE_MIN_INC * 256) *
+ IXGBE_ITR_ADAPTIVE_MIN_INC;
break;
- case bulk_latency:
- if (bytes_perint <= 20)
- itr_setting = low_latency;
+ case IXGBE_LINK_SPEED_2_5GB_FULL:
+ case IXGBE_LINK_SPEED_1GB_FULL:
+ case IXGBE_LINK_SPEED_10_FULL:
+ itr += DIV_ROUND_UP(avg_wire_size,
+ IXGBE_ITR_ADAPTIVE_MIN_INC * 64) *
+ IXGBE_ITR_ADAPTIVE_MIN_INC;
break;
}
- /* clear work counters since we have the values we need */
+clear_counts:
+ /* write back value */
+ ring_container->itr = itr;
+
+ /* next update should occur within next jiffy */
+ ring_container->next_update = next_update + 1;
+
ring_container->total_bytes = 0;
ring_container->total_packets = 0;
-
- /* write updated itr to ring container */
- ring_container->itr = itr_setting;
}
/**
static void ixgbe_set_itr(struct ixgbe_q_vector *q_vector)
{
- u32 new_itr = q_vector->itr;
- u8 current_itr;
+ u32 new_itr;
ixgbe_update_itr(q_vector, &q_vector->tx);
ixgbe_update_itr(q_vector, &q_vector->rx);
- current_itr = max(q_vector->rx.itr, q_vector->tx.itr);
+ /* use the smallest value of new ITR delay calculations */
+ new_itr = min(q_vector->rx.itr, q_vector->tx.itr);
- switch (current_itr) {
- /* counts and packets in update_itr are dependent on these numbers */
- case lowest_latency:
- new_itr = IXGBE_100K_ITR;
- break;
- case low_latency:
- new_itr = IXGBE_20K_ITR;
- break;
- case bulk_latency:
- new_itr = IXGBE_12K_ITR;
- break;
- default:
- break;
- }
+ /* Clear latency flag if set, shift into correct position */
+ new_itr &= ~IXGBE_ITR_ADAPTIVE_LATENCY;
+ new_itr <<= 2;
if (new_itr != q_vector->itr) {
- /* do an exponential smoothing */
- new_itr = (10 * new_itr * q_vector->itr) /
- ((9 * new_itr) + q_vector->itr);
-
/* save the algorithm value here */
q_vector->itr = new_itr;
projects / users / hch / configfs.git / commitdiff