i40e/i40evf: adjust interrupt throttle less frequently

The adaptive ITR (interrupt throttle rate) algorithm was adjusting
the hardware's interrupt rate too frequently.  This caused a lot
of variation in the interrupt rate for fairly constant workloads.

Change the code to have a counter and adjust only once every N
number of interrupts.

Change-ID: I0460f1f86571037484eca5aca36ac4d889cb8389
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index b7818be0f06dc0d85e79fa6a96c64b4c9bb5a495..7c2b2e891f62b3407521d4ebf63f2460e031344c 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -577,6 +577,8 @@ struct i40e_q_vector {
        struct rcu_head rcu;    /* to avoid race with update stats on free */
        char name[I40E_INT_NAME_STR_LEN];
        bool arm_wb_state;
+#define ITR_COUNTDOWN_START 100
+       u8 itr_countdown;       /* when 0 should adjust ITR */
 } ____cacheline_internodealigned_in_smp;
 
 /* lan device */

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 7d52092947dceebf8185a293b694a9bdca82dd42..e0142de018e6fccf000bd964002926390b0dd8cf 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -3087,6 +3087,7 @@ static void i40e_vsi_configure_msix(struct i40e_vsi *vsi)
        for (i = 0; i < vsi->num_q_vectors; i++, vector++) {
                struct i40e_q_vector *q_vector = vsi->q_vectors[i];
 
+               q_vector->itr_countdown = ITR_COUNTDOWN_START;
                q_vector->rx.itr = ITR_TO_REG(vsi->rx_itr_setting);
                q_vector->rx.latency_range = I40E_LOW_LATENCY;
                wr32(hw, I40E_PFINT_ITRN(I40E_RX_ITR, vector - 1),
@@ -3182,6 +3183,7 @@ static void i40e_configure_msi_and_legacy(struct i40e_vsi *vsi)
        u32 val;
 
        /* set the ITR configuration */
+       q_vector->itr_countdown = ITR_COUNTDOWN_START;
        q_vector->rx.itr = ITR_TO_REG(vsi->rx_itr_setting);
        q_vector->rx.latency_range = I40E_LOW_LATENCY;
        wr32(hw, I40E_PFINT_ITR0(I40E_RX_ITR), q_vector->rx.itr);

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 7aea14389d7b755d1eb337b43a46de72fd5731b8..006f0fb4720cf9afde5eff917a62ed56c239f670 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -845,10 +845,12 @@ static bool i40e_set_new_dynamic_itr(struct i40e_ring_container *rc)
         * The math works out because the divisor is in 10^(-6) which
         * turns the bytes/us input value into MB/s values, but
         * make sure to use usecs, as the register values written
-        * are in 2 usec increments in the ITR registers.
+        * are in 2 usec increments in the ITR registers, and make sure
+        * to use the smoothed values that the countdown timer gives us.
         */
-       usecs = (rc->itr << 1);
+       usecs = (rc->itr << 1) * ITR_COUNTDOWN_START;
        bytes_per_int = rc->total_bytes / usecs;
+
        switch (new_latency_range) {
        case I40E_LOWEST_LATENCY:
                if (bytes_per_int > 10)
@@ -1806,8 +1808,17 @@ static inline void i40e_update_enable_itr(struct i40e_vsi *vsi,
 
        vector = (q_vector->v_idx + vsi->base_vector);
 
+       /* avoid dynamic calculation if in countdown mode OR if
+        * all dynamic is disabled
+        */
        rxval = txval = i40e_buildreg_itr(I40E_ITR_NONE, 0);
 
+       if (q_vector->itr_countdown > 0 ||
+           (!ITR_IS_DYNAMIC(vsi->rx_itr_setting) &&
+            !ITR_IS_DYNAMIC(vsi->tx_itr_setting))) {
+               goto enable_int;
+       }
+
        if (ITR_IS_DYNAMIC(vsi->rx_itr_setting)) {
                rx = i40e_set_new_dynamic_itr(&q_vector->rx);
                rxval = i40e_buildreg_itr(I40E_RX_ITR, q_vector->rx.itr);
@@ -1845,8 +1856,15 @@ static inline void i40e_update_enable_itr(struct i40e_vsi *vsi,
                wr32(hw, INTREG(vector - 1), rxval);
        }
 
+enable_int:
        if (!test_bit(__I40E_DOWN, &vsi->state))
                wr32(hw, INTREG(vector - 1), txval);
+
+       if (q_vector->itr_countdown)
+               q_vector->itr_countdown--;
+       else
+               q_vector->itr_countdown = ITR_COUNTDOWN_START;
+
 }
 
 /**

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
index 0fe7eb77cae5eb05eb7adeccd4ab108f99dfaf1d..6779fb771d6af9b9c8fcf46fd56ccb498c2951e3 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
@@ -38,8 +38,8 @@
 #define I40E_ITR_8K                0x003E
 #define I40E_ITR_4K                0x007A
 #define I40E_MAX_INTRL             0x3B    /* reg uses 4 usec resolution */
-#define I40E_ITR_RX_DEF            I40E_ITR_8K
-#define I40E_ITR_TX_DEF            I40E_ITR_4K
+#define I40E_ITR_RX_DEF            I40E_ITR_20K
+#define I40E_ITR_TX_DEF            I40E_ITR_20K
 #define I40E_ITR_DYNAMIC           0x8000  /* use top bit as a flag */
 #define I40E_MIN_INT_RATE          250     /* ~= 1000000 / (I40E_MAX_ITR * 2) */
 #define I40E_MAX_INT_RATE          500000  /* == 1000000 / (I40E_MIN_ITR * 2) */

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index d76fe4a948dfff62ac8fd7bd17eaf6f29ab1a2ff..47e9a90d6b100d9874c6a6e77e123c7e5ccc7ac2 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -348,10 +348,12 @@ static bool i40e_set_new_dynamic_itr(struct i40e_ring_container *rc)
         * The math works out because the divisor is in 10^(-6) which
         * turns the bytes/us input value into MB/s values, but
         * make sure to use usecs, as the register values written
-        * are in 2 usec increments in the ITR registers.
+        * are in 2 usec increments in the ITR registers, and make sure
+        * to use the smoothed values that the countdown timer gives us.
         */
-       usecs = (rc->itr << 1);
+       usecs = (rc->itr << 1) * ITR_COUNTDOWN_START;
        bytes_per_int = rc->total_bytes / usecs;
+
        switch (new_latency_range) {
        case I40E_LOWEST_LATENCY:
                if (bytes_per_int > 10)
@@ -1245,8 +1247,18 @@ static inline void i40e_update_enable_itr(struct i40e_vsi *vsi,
        int vector;
 
        vector = (q_vector->v_idx + vsi->base_vector);
+
+       /* avoid dynamic calculation if in countdown mode OR if
+        * all dynamic is disabled
+        */
        rxval = txval = i40e_buildreg_itr(I40E_ITR_NONE, 0);
 
+       if (q_vector->itr_countdown > 0 ||
+           (!ITR_IS_DYNAMIC(vsi->rx_itr_setting) &&
+            !ITR_IS_DYNAMIC(vsi->tx_itr_setting))) {
+               goto enable_int;
+       }
+
        if (ITR_IS_DYNAMIC(vsi->rx_itr_setting)) {
                rx = i40e_set_new_dynamic_itr(&q_vector->rx);
                rxval = i40e_buildreg_itr(I40E_RX_ITR, q_vector->rx.itr);
@@ -1282,8 +1294,15 @@ static inline void i40e_update_enable_itr(struct i40e_vsi *vsi,
                wr32(hw, INTREG(vector - 1), rxval);
        }
 
+enable_int:
        if (!test_bit(__I40E_DOWN, &vsi->state))
                wr32(hw, INTREG(vector - 1), txval);
+
+       if (q_vector->itr_countdown)
+               q_vector->itr_countdown--;
+       else
+               q_vector->itr_countdown = ITR_COUNTDOWN_START;
+
 }
 
 /**

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
index e2352b886b77e9c95d1bfcb38302791dec4b4f5c..ebc1bf77f03606fb05312b2a5c84e788b92435cb 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
@@ -38,8 +38,8 @@
 #define I40E_ITR_8K                0x003E
 #define I40E_ITR_4K                0x007A
 #define I40E_MAX_INTRL             0x3B    /* reg uses 4 usec resolution */
-#define I40E_ITR_RX_DEF            I40E_ITR_8K
-#define I40E_ITR_TX_DEF            I40E_ITR_4K
+#define I40E_ITR_RX_DEF            I40E_ITR_20K
+#define I40E_ITR_TX_DEF            I40E_ITR_20K
 #define I40E_ITR_DYNAMIC           0x8000  /* use top bit as a flag */
 #define I40E_MIN_INT_RATE          250     /* ~= 1000000 / (I40E_MAX_ITR * 2) */
 #define I40E_MAX_INT_RATE          500000  /* == 1000000 / (I40E_MIN_ITR * 2) */

diff --git a/drivers/net/ethernet/intel/i40evf/i40evf.h b/drivers/net/ethernet/intel/i40evf/i40evf.h
index 22841c619f37a0d358e867a374532792976280a3..22fc3d49c4b95233fe1103aa92b95e5f97ecf6ba 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40evf.h
+++ b/drivers/net/ethernet/intel/i40evf/i40evf.h
@@ -112,6 +112,8 @@ struct i40e_q_vector {
        struct i40e_ring_container tx;
        u32 ring_mask;
        u8 num_ringpairs;       /* total number of ring pairs in vector */
+#define ITR_COUNTDOWN_START 100
+       u8 itr_countdown;       /* when 0 or 1 update ITR */
        int v_idx;        /* vector index in list */
        char name[IFNAMSIZ + 9];
        bool arm_wb_state;

diff --git a/drivers/net/ethernet/intel/i40evf/i40evf_main.c b/drivers/net/ethernet/intel/i40evf/i40evf_main.c
index ce997902f5a391cf079d8cdc5db67add18ad2d30..a44a42bb83c032a93e70bf27fad86299fcba01d2 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40evf_main.c
+++ b/drivers/net/ethernet/intel/i40evf/i40evf_main.c
@@ -357,6 +357,7 @@ i40evf_map_vector_to_rxq(struct i40evf_adapter *adapter, int v_idx, int r_idx)
        q_vector->rx.ring = rx_ring;
        q_vector->rx.count++;
        q_vector->rx.latency_range = I40E_LOW_LATENCY;
+       q_vector->itr_countdown = ITR_COUNTDOWN_START;
 }
 
 /**
@@ -377,6 +378,7 @@ i40evf_map_vector_to_txq(struct i40evf_adapter *adapter, int v_idx, int t_idx)
        q_vector->tx.ring = tx_ring;
        q_vector->tx.count++;
        q_vector->tx.latency_range = I40E_LOW_LATENCY;
+       q_vector->itr_countdown = ITR_COUNTDOWN_START;
        q_vector->num_ringpairs++;
        q_vector->ring_mask |= BIT(t_idx);
 }