iwlwifi: mvm: rs: fix and cleanup rs_get_rate_action

Change the down/upscale decision logic a bit to be based
on different success ratio thresholds. This fixes the implementation
compared to the rate scale algorithm which was planned to yield
optimal results. Also fix a case where a lower rate wasn't explored
despite being a potential for better throughput.
While at it rewrite rs_get_rate_action to be more clear and clean.

Cc: <stable@vger.kernel.org> [3.14]
Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

diff --git a/drivers/net/wireless/iwlwifi/mvm/rs.c b/drivers/net/wireless/iwlwifi/mvm/rs.c
index cd32ad5..97b8fac 100644 (file)
--- a/drivers/net/wireless/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/iwlwifi/mvm/rs.c
@@ -1658,85 +1658,76 @@ static enum rs_action rs_get_rate_action(struct iwl_mvm *mvm,
 {
        enum rs_action action = RS_ACTION_STAY;
 
-       /* Too many failures, decrease rate */
        if ((sr <= RS_SR_FORCE_DECREASE) || (current_tpt == 0)) {
                IWL_DEBUG_RATE(mvm,
-                              "decrease rate because of low SR\n");
-               action = RS_ACTION_DOWNSCALE;
-       /* No throughput measured yet for adjacent rates; try increase. */
-       } else if ((low_tpt == IWL_INVALID_VALUE) &&
-                  (high_tpt == IWL_INVALID_VALUE)) {
-               if (high != IWL_RATE_INVALID && sr >= IWL_RATE_INCREASE_TH) {
-                       IWL_DEBUG_RATE(mvm,
-                                      "Good SR and no high rate measurement. "
-                                      "Increase rate\n");
-                       action = RS_ACTION_UPSCALE;
-               } else if (low != IWL_RATE_INVALID) {
-                       IWL_DEBUG_RATE(mvm,
-                                      "Remain in current rate\n");
-                       action = RS_ACTION_STAY;
-               }
+                              "Decrease rate because of low SR\n");
+               return RS_ACTION_DOWNSCALE;
        }
 
-       /* Both adjacent throughputs are measured, but neither one has better
-        * throughput; we're using the best rate, don't change it!
-        */
-       else if ((low_tpt != IWL_INVALID_VALUE) &&
-                (high_tpt != IWL_INVALID_VALUE) &&
-                (low_tpt < current_tpt) &&
-                (high_tpt < current_tpt)) {
+       if ((low_tpt == IWL_INVALID_VALUE) &&
+           (high_tpt == IWL_INVALID_VALUE) &&
+           (high != IWL_RATE_INVALID)) {
                IWL_DEBUG_RATE(mvm,
-                              "Both high and low are worse. "
-                              "Maintain rate\n");
-               action = RS_ACTION_STAY;
+                              "No data about high/low rates. Increase rate\n");
+               return RS_ACTION_UPSCALE;
        }
 
-       /* At least one adjacent rate's throughput is measured,
-        * and may have better performance.
-        */
-       else {
-               /* Higher adjacent rate's throughput is measured */
-               if (high_tpt != IWL_INVALID_VALUE) {
-                       /* Higher rate has better throughput */
-                       if (high_tpt > current_tpt &&
-                           sr >= IWL_RATE_INCREASE_TH) {
-                               IWL_DEBUG_RATE(mvm,
-                                              "Higher rate is better and good "
-                                              "SR. Increate rate\n");
-                               action = RS_ACTION_UPSCALE;
-                       } else {
-                               IWL_DEBUG_RATE(mvm,
-                                              "Higher rate isn't better OR "
-                                              "no good SR. Maintain rate\n");
-                               action = RS_ACTION_STAY;
-                       }
+       if ((high_tpt == IWL_INVALID_VALUE) &&
+           (high != IWL_RATE_INVALID) &&
+           (low_tpt != IWL_INVALID_VALUE) &&
+           (low_tpt < current_tpt)) {
+               IWL_DEBUG_RATE(mvm,
+                              "No data about high rate and low rate is worse. Increase rate\n");
+               return RS_ACTION_UPSCALE;
+       }
 
-               /* Lower adjacent rate's throughput is measured */
-               } else if (low_tpt != IWL_INVALID_VALUE) {
-                       /* Lower rate has better throughput */
-                       if (low_tpt > current_tpt) {
-                               IWL_DEBUG_RATE(mvm,
-                                              "Lower rate is better. "
-                                              "Decrease rate\n");
-                               action = RS_ACTION_DOWNSCALE;
-                       } else if (sr >= IWL_RATE_INCREASE_TH) {
-                               IWL_DEBUG_RATE(mvm,
-                                              "Lower rate isn't better and "
-                                              "good SR. Increase rate\n");
-                               action = RS_ACTION_UPSCALE;
-                       }
-               }
+       if ((high_tpt != IWL_INVALID_VALUE) &&
+           (high_tpt > current_tpt)) {
+               IWL_DEBUG_RATE(mvm,
+                              "Higher rate is better. Increate rate\n");
+               return RS_ACTION_UPSCALE;
        }
 
-       /* Sanity check; asked for decrease, but success rate or throughput
-        * has been good at old rate.  Don't change it.
-        */
-       if ((action == RS_ACTION_DOWNSCALE) && (low != IWL_RATE_INVALID) &&
-           ((sr > IWL_RATE_HIGH_TH) ||
-            (current_tpt > (100 * tbl->expected_tpt[low])))) {
+       if ((low_tpt != IWL_INVALID_VALUE) &&
+           (high_tpt != IWL_INVALID_VALUE) &&
+           (low_tpt < current_tpt) &&
+           (high_tpt < current_tpt)) {
                IWL_DEBUG_RATE(mvm,
-                              "Sanity check failed. Maintain rate\n");
-               action = RS_ACTION_STAY;
+                              "Both high and low are worse. Maintain rate\n");
+               return RS_ACTION_STAY;
+       }
+
+       if ((low_tpt != IWL_INVALID_VALUE) &&
+           (low_tpt > current_tpt)) {
+               IWL_DEBUG_RATE(mvm,
+                              "Lower rate is better\n");
+               action = RS_ACTION_DOWNSCALE;
+               goto out;
+       }
+
+       if ((low_tpt == IWL_INVALID_VALUE) &&
+           (low != IWL_RATE_INVALID)) {
+               IWL_DEBUG_RATE(mvm,
+                              "No data about lower rate\n");
+               action = RS_ACTION_DOWNSCALE;
+               goto out;
+       }
+
+       IWL_DEBUG_RATE(mvm, "Maintain rate\n");
+
+out:
+       if ((action == RS_ACTION_DOWNSCALE) && (low != IWL_RATE_INVALID)) {
+               if (sr >= RS_SR_NO_DECREASE) {
+                       IWL_DEBUG_RATE(mvm,
+                                      "SR is above NO DECREASE. Avoid downscale\n");
+                       action = RS_ACTION_STAY;
+               } else if (current_tpt > (100 * tbl->expected_tpt[low])) {
+                       IWL_DEBUG_RATE(mvm,
+                                      "Current TPT is higher than max expected in low rate. Avoid downscale\n");
+                       action = RS_ACTION_STAY;
+               } else {
+                       IWL_DEBUG_RATE(mvm, "Decrease rate\n");
+               }
        }
 
        return action;

diff --git a/drivers/net/wireless/iwlwifi/mvm/rs.h b/drivers/net/wireless/iwlwifi/mvm/rs.h
index 9892d92..fbb476a 100644 (file)
--- a/drivers/net/wireless/iwlwifi/mvm/rs.h
+++ b/drivers/net/wireless/iwlwifi/mvm/rs.h
@@ -156,6 +156,7 @@ enum {
 #define IWL_RATE_HIGH_TH               10880   /*  85% */
 #define IWL_RATE_INCREASE_TH           6400    /*  50% */
 #define RS_SR_FORCE_DECREASE           1920    /*  15% */
+#define RS_SR_NO_DECREASE              10880   /*  85% */
 
 #define LINK_QUAL_AGG_TIME_LIMIT_DEF   (4000) /* 4 milliseconds */
 #define LINK_QUAL_AGG_TIME_LIMIT_MAX   (8000)