mac80211: add documentation and verbose variable names in

Add documentation and more verbose variable names to minstrel's multi-rate-retry setup within function minstrel_get_rate() to increase the readability of the algorithm. Acked-by: Felix Fietkau <nbd@openwrt.org> Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de> Signed-off-by: Johannes Berg <johannes.berg@intel.com>

mac80211: add documentation and verbose variable names in
Add documentation and more verbose variable names to minstrel's multi-rate-retry setup within function minstrel_get_rate() to increase the readability of the algorithm. Acked-by: Felix Fietkau <nbd@openwrt.org> Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Thomas Huehn · Johannes Berg
1 parent c8ca8c2f93
Showing 2 changed files with 50 additions and 33 deletions Side-by-side Diff
net/mac80211/rc80211_minstrel.c
net/mac80211/rc80211_minstrel.h
@@ -78,7 +78,6 @@
 	u32 usecs;
 	int i;
  
-	mi->stats_update = jiffies;
 	for (i = 0; i < mi->n_rates; i++) {
 		struct minstrel_rate *mr = &mi->r[i];
  
@@ -144,6 +143,9 @@
 	mi->max_tp_rate = index_max_tp;
 	mi->max_tp_rate2 = index_max_tp2;
 	mi->max_prob_rate = index_max_prob;
+
+	/* Reset update timer */
+	mi->stats_update = jiffies;
 }
  
 static void
@@ -204,10 +206,10 @@
 minstrel_get_next_sample(struct minstrel_sta_info *mi)
 {
 	unsigned int sample_ndx;
-	sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
-	mi->sample_idx++;
-	if ((int) mi->sample_idx > (mi->n_rates - 2)) {
-		mi->sample_idx = 0;
+	sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
+	mi->sample_row++;
+	if ((int) mi->sample_row > (mi->n_rates - 2)) {
+		mi->sample_row = 0;
 		mi->sample_column++;
 		if (mi->sample_column >= SAMPLE_COLUMNS)
 			mi->sample_column = 0;
  
  
  
  
  
  
  
@@ -225,31 +227,37 @@
 	struct minstrel_priv *mp = priv;
 	struct ieee80211_tx_rate *ar = info->control.rates;
 	unsigned int ndx, sample_ndx = 0;
-	bool mrr;
-	bool sample_slower = false;
-	bool sample = false;
+	bool mrr_capable;
+	bool indirect_rate_sampling = false;
+	bool rate_sampling = false;
 	int i, delta;
 	int mrr_ndx[3];
-	int sample_rate;
+	int sampling_ratio;
  
+	/* management/no-ack frames do not use rate control */
 	if (rate_control_send_low(sta, priv_sta, txrc))
 		return;
  
-	mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
+	/* check multi-rate-retry capabilities & adjust lookaround_rate */
+	mrr_capable = mp->has_mrr &&
+		      !txrc->rts &&
+		      !txrc->bss_conf->use_cts_prot;
+	if (mrr_capable)
+		sampling_ratio = mp->lookaround_rate_mrr;
+	else
+		sampling_ratio = mp->lookaround_rate;
  
+	/* init rateindex [ndx] with max throughput rate */
 	ndx = mi->max_tp_rate;
  
-	if (mrr)
-		sample_rate = mp->lookaround_rate_mrr;
-	else
-		sample_rate = mp->lookaround_rate;
-
+	/* increase sum packet counter */
 	mi->packet_count++;
-	delta = (mi->packet_count * sample_rate / 100) -
+
+	delta = (mi->packet_count * sampling_ratio / 100) -
 			(mi->sample_count + mi->sample_deferred / 2);
  
 	/* delta > 0: sampling required */
-	if ((delta > 0) && (mrr || !mi->prev_sample)) {
+	if ((delta > 0) && (mrr_capable || !mi->prev_sample)) {
 		struct minstrel_rate *msr;
 		if (mi->packet_count >= 10000) {
 			mi->sample_deferred = 0;
  
  
  
@@ -268,21 +276,25 @@
 			mi->sample_count += (delta - mi->n_rates * 2);
 		}
  
+		/* get next random rate sample */
 		sample_ndx = minstrel_get_next_sample(mi);
 		msr = &mi->r[sample_ndx];
-		sample = true;
-		sample_slower = mrr && (msr->perfect_tx_time >
-			mi->r[ndx].perfect_tx_time);
+		rate_sampling = true;
  
-		if (!sample_slower) {
+		/* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
+		 * rate sampling method should be used */
+		if (mrr_capable &&
+		    msr->perfect_tx_time > mi->r[ndx].perfect_tx_time)
+				indirect_rate_sampling = true;
+
+		if (!indirect_rate_sampling) {
 			if (msr->sample_limit != 0) {
 				ndx = sample_ndx;
 				mi->sample_count++;
 				if (msr->sample_limit > 0)
 					msr->sample_limit--;
-			} else {
-				sample = false;
-			}
+			} else
+				rate_sampling = false;
 		} else {
 			/* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
 			 * packets that have the sampling rate deferred to the
  
  
  
  
  
@@ -294,34 +306,39 @@
 			mi->sample_deferred++;
 		}
 	}
-	mi->prev_sample = sample;
+	mi->prev_sample = rate_sampling;
  
 	/* If we're not using MRR and the sampling rate already
 	 * has a probability of >95%, we shouldn't be attempting
 	 * to use it, as this only wastes precious airtime */
-	if (!mrr && sample && (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
+	if (!mrr_capable && rate_sampling &&
+	   (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
 		ndx = mi->max_tp_rate;
  
+	/* mrr setup for 1st stage */
 	ar[0].idx = mi->r[ndx].rix;
 	ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
  
-	if (!mrr) {
-		if (!sample)
+	/* non mrr setup for 2nd stage */
+	if (!mrr_capable) {
+		if (!rate_sampling)
 			ar[0].count = mp->max_retry;
 		ar[1].idx = mi->lowest_rix;
 		ar[1].count = mp->max_retry;
 		return;
 	}
  
-	/* MRR setup */
-	if (sample) {
-		if (sample_slower)
+	/* mrr setup for 2nd stage */
+	if (rate_sampling) {
+		if (indirect_rate_sampling)
 			mrr_ndx[0] = sample_ndx;
 		else
 			mrr_ndx[0] = mi->max_tp_rate;
 	} else {
 		mrr_ndx[0] = mi->max_tp_rate2;
 	}
+
+	/* mrr setup for 3rd & 4th stage */
 	mrr_ndx[1] = mi->max_prob_rate;
 	mrr_ndx[2] = 0;
 	for (i = 1; i < 4; i++) {
@@ -352,7 +369,7 @@
 	u8 rnd[8];
  
 	mi->sample_column = 0;
-	mi->sample_idx = 0;
+	mi->sample_row = 0;
 	memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
  
 	for (col = 0; col < SAMPLE_COLUMNS; col++) {
@@ -69,7 +69,7 @@
 	unsigned int sample_count;
 	int sample_deferred;
  
-	unsigned int sample_idx;
+	unsigned int sample_row;
 	unsigned int sample_column;
  
 	int n_rates;
...	...	@@ -78,7 +78,6 @@
78	78	u32 usecs;
79	79	int i;
80	80
81		- mi->stats_update = jiffies;
82	81	for (i = 0; i < mi->n_rates; i++) {
83	82	struct minstrel_rate *mr = &mi->r[i];
84	83
...	...	@@ -144,6 +143,9 @@
144	143	mi->max_tp_rate = index_max_tp;
145	144	mi->max_tp_rate2 = index_max_tp2;
146	145	mi->max_prob_rate = index_max_prob;
	146	+
	147	+ /* Reset update timer */
	148	+ mi->stats_update = jiffies;
147	149	}
148	150
149	151	static void
...	...	@@ -204,10 +206,10 @@
204	206	minstrel_get_next_sample(struct minstrel_sta_info *mi)
205	207	{
206	208	unsigned int sample_ndx;
207		- sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
208		- mi->sample_idx++;
209		- if ((int) mi->sample_idx > (mi->n_rates - 2)) {
210		- mi->sample_idx = 0;
	209	+ sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
	210	+ mi->sample_row++;
	211	+ if ((int) mi->sample_row > (mi->n_rates - 2)) {
	212	+ mi->sample_row = 0;
211	213	mi->sample_column++;
212	214	if (mi->sample_column >= SAMPLE_COLUMNS)
213	215	mi->sample_column = 0;
214	216
215	217
216	218
217	219
218	220
219	221
220	222
...	...	@@ -225,31 +227,37 @@
225	227	struct minstrel_priv *mp = priv;
226	228	struct ieee80211_tx_rate *ar = info->control.rates;
227	229	unsigned int ndx, sample_ndx = 0;
228		- bool mrr;
229		- bool sample_slower = false;
230		- bool sample = false;
	230	+ bool mrr_capable;
	231	+ bool indirect_rate_sampling = false;
	232	+ bool rate_sampling = false;
231	233	int i, delta;
232	234	int mrr_ndx[3];
233		- int sample_rate;
	235	+ int sampling_ratio;
234	236
	237	+ /* management/no-ack frames do not use rate control */
235	238	if (rate_control_send_low(sta, priv_sta, txrc))
236	239	return;
237	240
238		- mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
	241	+ /* check multi-rate-retry capabilities & adjust lookaround_rate */
	242	+ mrr_capable = mp->has_mrr &&
	243	+ !txrc->rts &&
	244	+ !txrc->bss_conf->use_cts_prot;
	245	+ if (mrr_capable)
	246	+ sampling_ratio = mp->lookaround_rate_mrr;
	247	+ else
	248	+ sampling_ratio = mp->lookaround_rate;
239	249
	250	+ /* init rateindex [ndx] with max throughput rate */
240	251	ndx = mi->max_tp_rate;
241	252
242		- if (mrr)
243		- sample_rate = mp->lookaround_rate_mrr;
244		- else
245		- sample_rate = mp->lookaround_rate;
246		-
	253	+ /* increase sum packet counter */
247	254	mi->packet_count++;
248		- delta = (mi->packet_count * sample_rate / 100) -
	255	+
	256	+ delta = (mi->packet_count * sampling_ratio / 100) -
249	257	(mi->sample_count + mi->sample_deferred / 2);
250	258
251	259	/* delta > 0: sampling required */
252		- if ((delta > 0) && (mrr \|\| !mi->prev_sample)) {
	260	+ if ((delta > 0) && (mrr_capable \|\| !mi->prev_sample)) {
253	261	struct minstrel_rate *msr;
254	262	if (mi->packet_count >= 10000) {
255	263	mi->sample_deferred = 0;
256	264
257	265
258	266
...	...	@@ -268,21 +276,25 @@
268	276	mi->sample_count += (delta - mi->n_rates * 2);
269	277	}
270	278
	279	+ /* get next random rate sample */
271	280	sample_ndx = minstrel_get_next_sample(mi);
272	281	msr = &mi->r[sample_ndx];
273		- sample = true;
274		- sample_slower = mrr && (msr->perfect_tx_time >
275		- mi->r[ndx].perfect_tx_time);
	282	+ rate_sampling = true;
276	283
277		- if (!sample_slower) {
	284	+ /* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
	285	+ * rate sampling method should be used */
	286	+ if (mrr_capable &&
	287	+ msr->perfect_tx_time > mi->r[ndx].perfect_tx_time)
	288	+ indirect_rate_sampling = true;
	289	+
	290	+ if (!indirect_rate_sampling) {
278	291	if (msr->sample_limit != 0) {
279	292	ndx = sample_ndx;
280	293	mi->sample_count++;
281	294	if (msr->sample_limit > 0)
282	295	msr->sample_limit--;
283		- } else {
284		- sample = false;
285		- }
	296	+ } else
	297	+ rate_sampling = false;
286	298	} else {
287	299	/* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
288	300	* packets that have the sampling rate deferred to the
289	301
290	302
291	303
292	304
293	305
...	...	@@ -294,34 +306,39 @@
294	306	mi->sample_deferred++;
295	307	}
296	308	}
297		- mi->prev_sample = sample;
	309	+ mi->prev_sample = rate_sampling;
298	310
299	311	/* If we're not using MRR and the sampling rate already
300	312	* has a probability of >95%, we shouldn't be attempting
301	313	* to use it, as this only wastes precious airtime */
302		- if (!mrr && sample && (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
	314	+ if (!mrr_capable && rate_sampling &&
	315	+ (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
303	316	ndx = mi->max_tp_rate;
304	317
	318	+ /* mrr setup for 1st stage */
305	319	ar[0].idx = mi->r[ndx].rix;
306	320	ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
307	321
308		- if (!mrr) {
309		- if (!sample)
	322	+ /* non mrr setup for 2nd stage */
	323	+ if (!mrr_capable) {
	324	+ if (!rate_sampling)
310	325	ar[0].count = mp->max_retry;
311	326	ar[1].idx = mi->lowest_rix;
312	327	ar[1].count = mp->max_retry;
313	328	return;
314	329	}
315	330
316		- /* MRR setup */
317		- if (sample) {
318		- if (sample_slower)
	331	+ /* mrr setup for 2nd stage */
	332	+ if (rate_sampling) {
	333	+ if (indirect_rate_sampling)
319	334	mrr_ndx[0] = sample_ndx;
320	335	else
321	336	mrr_ndx[0] = mi->max_tp_rate;
322	337	} else {
323	338	mrr_ndx[0] = mi->max_tp_rate2;
324	339	}
	340	+
	341	+ /* mrr setup for 3rd & 4th stage */
325	342	mrr_ndx[1] = mi->max_prob_rate;
326	343	mrr_ndx[2] = 0;
327	344	for (i = 1; i < 4; i++) {
...	...	@@ -352,7 +369,7 @@
352	369	u8 rnd[8];
353	370
354	371	mi->sample_column = 0;
355		- mi->sample_idx = 0;
	372	+ mi->sample_row = 0;
356	373	memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
357	374
358	375	for (col = 0; col < SAMPLE_COLUMNS; col++) {
...	...	@@ -69,7 +69,7 @@
69	69	unsigned int sample_count;
70	70	int sample_deferred;
71	71
72		- unsigned int sample_idx;
	72	+ unsigned int sample_row;
73	73	unsigned int sample_column;
74	74
75	75	int n_rates;