anolis: dim: optimize dim lib

ANBZ: #8042

Tune the dim algorithm.

We need to void the impact of virtio's dim optimization
on other nics.

Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Link: https://gitee.com/anolis/cloud-kernel/pulls/3227

drivers/net/virtio_net.c

@@ -52,6 +52,9 @@ module_param(napi_tx, bool, 0644);
 module_param(force_xdp, bool, 0644);
 module_param(lro, bool, 0644);
 
+#define VIRTNET_DIM_TUNE_TRAFFIC 1
+#define VIRTNET_DIM_NEVENTS 128
+
 /* FIXME: MTU in config. */
 #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN	128
@@ -1979,7 +1982,8 @@ static void virtnet_rx_dim_update(struct virtnet_info *vi, struct receive_queue
 			  &cur_sample);
 	u64_stats_update_end(&rq->stats.syncp);
 
-	net_dim(&rq->dim, cur_sample);
+	net_dim_tune(&rq->dim, cur_sample, VIRTNET_DIM_NEVENTS,
+		     VIRTNET_DIM_TUNE_TRAFFIC);
 	rq->packets_in_napi = 0;
 }
 

include/linux/dim.h

@@ -25,6 +25,8 @@ struct net_device;
  */
 #define DIM_NEVENTS 64
 
+#define DIM_RATIO 5
+
 /*
  * Is a difference between values justifies taking an action.
  * We consider 10% difference as significant.
@@ -32,6 +34,10 @@ struct net_device;
 #define IS_SIGNIFICANT_DIFF(val, ref) \
 	((ref) && (((100UL * abs((val) - (ref))) / (ref)) > 10))
 
+/* Consider 1% difference as traffic is stable. */
+#define IS_SIGNIFICANT_DIFF_1(val, ref) \
+	((ref) && (((100UL * abs((val) - (ref))) / (ref)) <= 1))
+
 /*
  * Calculate the gap between two values.
  * Take wrap-around and variable size into consideration.
@@ -425,6 +431,18 @@ struct dim_cq_moder net_dim_get_def_tx_moderation(u8 cq_period_mode);
  */
 void net_dim(struct dim *dim, struct dim_sample end_sample);
 
+/**
+ *	net_dim_tune - DIM algorithm entry point with tunable params
+ *	@dim: DIM instance information
+ *	@end_sample: Current data measurement
+ *	@sample_events: Sampling event interval
+ *	@tune_traffic: non-high load traffic decision optimization
+ *
+ * This provides more tuning parameter settings than the net_dim interface.
+ */
+void net_dim_tune(struct dim *dim, struct dim_sample end_sample,
+		  u16 sample_events, bool tune_traffic);
+
 /* RDMA DIM */
 
 /*

lib/dim/dim.c

@@ -64,13 +64,15 @@ void dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
 			     start->byte_ctr);
 	u32 ncomps = BIT_GAP(BITS_PER_TYPE(u32), end->comp_ctr,
 			     start->comp_ctr);
+	u16 nevents = BIT_GAP(BITS_PER_TYPE(u16), end->event_ctr,
+			      start->event_ctr);
 
 	if (!delta_us)
 		return;
 
 	curr_stats->ppms = DIV_ROUND_UP(npkts * USEC_PER_MSEC, delta_us);
 	curr_stats->bpms = DIV_ROUND_UP(nbytes * USEC_PER_MSEC, delta_us);
-	curr_stats->epms = DIV_ROUND_UP(DIM_NEVENTS * USEC_PER_MSEC,
+	curr_stats->epms = DIV_ROUND_UP(nevents * USEC_PER_MSEC,
 					delta_us);
 	curr_stats->cpms = DIV_ROUND_UP(ncomps * USEC_PER_MSEC, delta_us);
 	if (curr_stats->epms != 0)

lib/dim/net_dim.c

@@ -294,7 +294,8 @@ static int net_dim_stats_compare(struct dim_stats *curr,
 	return DIM_STATS_SAME;
 }
 
-static bool net_dim_decision(struct dim_stats *curr_stats, struct dim *dim)
+static bool net_dim_decision(struct dim_stats *curr_stats, struct dim *dim,
+			     bool tune_traffic)
 {
 	int prev_state = dim->tune_state;
 	int prev_ix = dim->profile_ix;
@@ -317,6 +318,16 @@ static bool net_dim_decision(struct dim_stats *curr_stats, struct dim *dim)
 
 	case DIM_GOING_RIGHT:
 	case DIM_GOING_LEFT:
+		/* A new local optimum for tune. Other states are cleared.*/
+		if (tune_traffic && dim->prev_stats.ppms && curr_stats->epms &&
+		    IS_SIGNIFICANT_DIFF_1(curr_stats->ppms, dim->prev_stats.ppms) &&
+		    (curr_stats->ppms / curr_stats->epms) <= DIM_RATIO) {
+			dim_park_on_top(dim);
+			dim->profile_ix = 1;
+			dim->prev_stats = *curr_stats;
+			return true;
+		}
+
 		stats_res = net_dim_stats_compare(curr_stats,
 						  &dim->prev_stats);
 		if (stats_res != DIM_STATS_BETTER)
@@ -347,7 +358,8 @@ static bool net_dim_decision(struct dim_stats *curr_stats, struct dim *dim)
 	return dim->profile_ix != prev_ix;
 }
 
-void net_dim(struct dim *dim, struct dim_sample end_sample)
+static void net_dim_impl(struct dim *dim, struct dim_sample end_sample,
+			 u16 sample_events, bool tune_traffic)
 {
 	struct dim_stats curr_stats;
 	u16 nevents;
@@ -357,10 +369,15 @@ void net_dim(struct dim *dim, struct dim_sample end_sample)
 		nevents = BIT_GAP(BITS_PER_TYPE(u16),
 				  end_sample.event_ctr,
 				  dim->start_sample.event_ctr);
-		if (nevents < DIM_NEVENTS)
+		/* Compared with the timer method, judging the minimum
+		 * interval of an iteration with a larger sample_nevents
+		 * has a better results.
+		 */
+		if (nevents < sample_events)
 			break;
+
 		dim_calc_stats(&dim->start_sample, &end_sample, &curr_stats);
-		if (net_dim_decision(&curr_stats, dim)) {
+		if (net_dim_decision(&curr_stats, dim, tune_traffic)) {
 			dim->state = DIM_APPLY_NEW_PROFILE;
 			schedule_work(&dim->work);
 			break;
@@ -375,4 +392,16 @@ void net_dim(struct dim *dim, struct dim_sample end_sample)
 		break;
 	}
 }
+
+void net_dim(struct dim *dim, struct dim_sample end_sample)
+{
+	net_dim_impl(dim, end_sample, DIM_NEVENTS, false);
+}
 EXPORT_SYMBOL(net_dim);
+
+void net_dim_tune(struct dim *dim, struct dim_sample end_sample,
+		  u16 sample_events, bool tune_traffic)
+{
+	net_dim_impl(dim, end_sample, sample_events, tune_traffic);
+}
+EXPORT_SYMBOL(net_dim_tune);