+enum latency_range {
+ lowest_latency = 0,
+ low_latency = 1,
+ bulk_latency = 2,
+ latency_invalid = 255
+};
+
+/**
+ * e1000_update_itr - update the dynamic ITR value based on statistics
+ * Stores a new ITR value based on packets and byte
+ * counts during the last interrupt. The advantage of per interrupt
+ * computation is faster updates and more accurate ITR for the current
+ * 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 (see e1000_param.c)
+ * @adapter: pointer to adapter
+ * @itr_setting: current adapter->itr
+ * @packets: the number of packets during this measurement interval
+ * @bytes: the number of bytes during this measurement interval
+ **/
+static unsigned int e1000_update_itr(struct e1000_adapter *adapter,
+ uint16_t itr_setting,
+ int packets,
+ int bytes)
+{
+ unsigned int retval = itr_setting;
+ struct e1000_hw *hw = &adapter->hw;
+
+ if (unlikely(hw->mac_type < e1000_82540))
+ goto update_itr_done;
+
+ if (packets == 0)
+ goto update_itr_done;
+
+ switch (itr_setting) {
+ case lowest_latency:
+ /* jumbo frames get bulk treatment*/
+ if (bytes/packets > 8000)
+ retval = bulk_latency;
+ else if ((packets < 5) && (bytes > 512))
+ retval = low_latency;
+ break;
+ case low_latency: /* 50 usec aka 20000 ints/s */
+ if (bytes > 10000) {
+ /* jumbo frames need bulk latency setting */
+ if (bytes/packets > 8000)
+ retval = bulk_latency;
+ else if ((packets < 10) || ((bytes/packets) > 1200))
+ retval = bulk_latency;
+ else if ((packets > 35))
+ retval = lowest_latency;
+ } else if (bytes/packets > 2000)
+ retval = bulk_latency;
+ else if (packets <= 2 && bytes < 512)
+ retval = lowest_latency;
+ break;
+ case bulk_latency: /* 250 usec aka 4000 ints/s */
+ if (bytes > 25000) {
+ if (packets > 35)
+ retval = low_latency;
+ } else if (bytes < 6000) {
+ retval = low_latency;
+ }
+ break;
+ }
+
+update_itr_done:
+ return retval;
+}
+
+static void e1000_set_itr(struct e1000_adapter *adapter)
+{
+ struct e1000_hw *hw = &adapter->hw;
+ uint16_t current_itr;
+ uint32_t new_itr = adapter->itr;
+
+ if (unlikely(hw->mac_type < e1000_82540))
+ return;
+
+ /* for non-gigabit speeds, just fix the interrupt rate at 4000 */
+ if (unlikely(adapter->link_speed != SPEED_1000)) {
+ current_itr = 0;
+ new_itr = 4000;
+ goto set_itr_now;
+ }
+
+ adapter->tx_itr = e1000_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 = e1000_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;
+
+ current_itr = max(adapter->rx_itr, adapter->tx_itr);
+
+ switch (current_itr) {
+ /* counts and packets in update_itr are dependent on these numbers */
+ case lowest_latency:
+ new_itr = 70000;
+ break;
+ case low_latency:
+ new_itr = 20000; /* aka hwitr = ~200 */
+ break;
+ case bulk_latency:
+ new_itr = 4000;
+ break;
+ default:
+ break;
+ }
+
+set_itr_now:
+ if (new_itr != adapter->itr) {
+ /* 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;
+ E1000_WRITE_REG(hw, ITR, 1000000000 / (new_itr * 256));
+ }
+
+ return;
+}
+