Commit ed21a384 authored Sep 21, 2015 by Eyal Shapira Committed by Luca Coelho Oct 05, 2015

iwlwifi: mvm: rs: fix success ratio comparison in rs_get_best_rate



success_ratio is actually 128 * SR in percentage while
IWL_MVM_RS_SR_NO_DECREASE is 85%. Fix this by using RS_PERCENT().
This bug caused the if branch to be always executed. This in turn
led to always selecting a rate, following a column switch, in which
the expected throughput would exceed the best expected current throughput.
In some scenarios where the success ratio isn't >85% such a rate
could be too aggressive leading us to avoid the new column.
This has the potential of causing sub optimal performance.

Reported-by: Moshe Harel <moshe.harel@intel.com>
Signed-off-by: Eyal Shapira <eyalx.shapira@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

parent 40ce5ed1

drivers/net/wireless/iwlwifi/mvm/rs.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1527,7 +1527,7 @@ static s32 rs_get_best_rate(struct iwl_mvm *mvm,
		u32 target_tpt;
		int rate_idx;

		if (success_ratio > IWL_MVM_RS_SR_NO_DECREASE) {
		if (success_ratio >= RS_PERCENT(IWL_MVM_RS_SR_NO_DECREASE)) {
		target_tpt = 100 * expected_current_tpt;
		IWL_DEBUG_RATE(mvm,
		"SR %d high. Find rate exceeding EXPECTED_CURRENT %d\n",
		@@ -1535,7 +1535,7 @@ static s32 rs_get_best_rate(struct iwl_mvm *mvm,
		} else {
		target_tpt = lq_sta->last_tpt;
		IWL_DEBUG_RATE(mvm,
		"SR %d not thag good. Find rate exceeding ACTUAL_TPT %d\n",
		"SR %d not that good. Find rate exceeding ACTUAL_TPT %d\n",
		success_ratio, target_tpt);
		}