neigh_table_tuner: tune all thresholds and limit growth

increase all thresholds simultaneously instead of only gc_thresh3. Also set a
limit to how large the thresholds can grow

Signed-off-by: Pradyumn Rahar <pradyumn.rahar@oracle.com>

Author: Hannibal404

src/neigh_table_tuner.bpf.c

@@ -43,6 +43,8 @@ int BPF_PROG(bpftune_neigh_create, struct neigh_table *tbl,
 
 		new_tbl_stats.family = BPFTUNE_CORE_READ(tbl, family);
 		new_tbl_stats.entries = BPFTUNE_CORE_READ(tbl, entries.counter);
+		new_tbl_stats.thresh1 = BPFTUNE_CORE_READ(tbl, gc_thresh1);
+		new_tbl_stats.thresh2 = BPFTUNE_CORE_READ(tbl, gc_thresh2);
 		new_tbl_stats.max = BPFTUNE_CORE_READ(tbl, gc_thresh3);
 		if (dev) {
 			bpf_probe_read(&new_tbl_stats.dev, sizeof(new_tbl_stats.dev), dev);
@@ -55,12 +57,14 @@ int BPF_PROG(bpftune_neigh_create, struct neigh_table *tbl,
 	}
 	tbl_stats->entries = BPFTUNE_CORE_READ(tbl, entries.counter);
 	tbl_stats->gc_entries = BPFTUNE_CORE_READ(tbl, gc_entries.counter);
+	tbl_stats->thresh1 = BPFTUNE_CORE_READ(tbl, gc_thresh1);
+	tbl_stats->thresh2 = BPFTUNE_CORE_READ(tbl, gc_thresh2);
 	tbl_stats->max = BPFTUNE_CORE_READ(tbl, gc_thresh3);
 
 	/* exempt from gc entries are not subject to space constraints, but
  	 * do take up table entries.
  	 */
-	if (NEARLY_FULL(tbl_stats->entries, tbl_stats->max)) {
+	if (NEARLY_FULL(tbl_stats->entries, tbl_stats->max) && (tbl_stats->max < MAX_THRESH3)) {
 		struct neigh_parms *parms = BPFTUNE_CORE_READ(n, parms);
 		struct net *net = BPFTUNE_CORE_READ(parms, net.net);
 

src/neigh_table_tuner.c

@@ -77,7 +77,7 @@ void fini(struct bpftuner *tuner)
 	bpftuner_bpf_fini(tuner);
 }
 
-static int set_gc_thresh3(struct bpftuner *tuner, struct tbl_stats *stats)
+static int increase_thresh(struct bpftuner *tuner, struct tbl_stats *stats)
 {
 	char *tbl_name = stats->family == AF_INET ? "arp_cache" : "ndisc_cache";
 	/* Open raw socket for the NETLINK_ROUTE protocol */
@@ -89,6 +89,8 @@ static int set_gc_thresh3(struct bpftuner *tuner, struct tbl_stats *stats)
                 .ndtm_family = stats->family,
         };
 	struct nl_msg *m = NULL, *parms = NULL;
+	int new_gc_thresh1 = 0;
+	int new_gc_thresh2 = 0;
 	int new_gc_thresh3 = 0;
 	int ret;
 
@@ -120,7 +122,19 @@ static int set_gc_thresh3(struct bpftuner *tuner, struct tbl_stats *stats)
 	NLA_PUT_STRING(m, NDTA_NAME, tbl_name);
 
 	new_gc_thresh3 = BPFTUNE_GROW_BY_DELTA(stats->max);
+
+	if (new_gc_thresh3 >= MAX_THRESH3) {
+		new_gc_thresh3 = MAX_THRESH3;
+		new_gc_thresh2 = MAX_THRESH2;
+		new_gc_thresh1 = MAX_THRESH1;
+	}
+	else {
+		new_gc_thresh2 = BPFTUNE_GROW_BY_DELTA(stats->thresh2);
+		new_gc_thresh1 = BPFTUNE_GROW_BY_DELTA(stats->thresh1);
+	}
 	NLA_PUT_U32(m, NDTA_THRESH3, new_gc_thresh3);
+	NLA_PUT_U32(m, NDTA_THRESH2, new_gc_thresh2);
+	NLA_PUT_U32(m, NDTA_THRESH1, new_gc_thresh1);
 
 	parms = nlmsg_alloc();
 	if (!parms) {
@@ -152,8 +166,10 @@ static int set_gc_thresh3(struct bpftuner *tuner, struct tbl_stats *stats)
 			    stats->dev, strerror(-ret));
 	} else {
 		bpftuner_tunable_update(tuner, tunable, NEIGH_TABLE_FULL, 0,
-"updated gc_thresh3 for %s table, dev '%s' (ifindex %d) from %ld to %ld\n",
+"updated thresholds for %s table, dev '%s' (ifindex %d) thresh1: %ld to %ld, thresh2: %ld to %ld, thresh3: %ld to %ld\n",
 			    tbl_name, stats->dev, stats->ifindex,
+				stats->thresh1, new_gc_thresh1,
+				stats->thresh2, new_gc_thresh2,
 			    stats->max, new_gc_thresh3);
 	}
 	return ret;
@@ -169,7 +185,7 @@ void event_handler(struct bpftuner *tuner,
 	case NEIGH_TABLE_FULL:
 		if (bpftune_cap_add())
 			return;
-		set_gc_thresh3(tuner, stats);
+		increase_thresh(tuner, stats);
 		bpftune_cap_drop();
 		break;
 	default:

src/neigh_table_tuner.h

@@ -23,6 +23,10 @@
 #define IFNAMSIZ 16
 #endif
 
+#define MAX_THRESH1 4096
+#define MAX_THRESH2 16384
+#define MAX_THRESH3 32768
+
 enum neigh_table_tunables {
 	NEIGH_TABLE_IPV4_GC_INTERVAL,
 	NEIGH_TABLE_IPV4_GC_STALE_TIME,
@@ -45,6 +49,8 @@ struct tbl_stats {
 	int family;
 	int entries;
 	int gc_entries;
+	int thresh1;
+	int thresh2;
 	int max;
 	int ifindex;
 	char dev[IFNAMSIZ];