ipv6: reduce per device ICMP mib sizes

ipv6 has per device ICMP SNMP counters, taking too much space because
they use percpu storage.

needed size per device is :
(512+4)*sizeof(long)*number_of_possible_cpus*2

On a 32bit kernel, 16 possible cpus, this wastes more than 64kbytes of
memory per ipv6 enabled network device, taken in vmalloc pool.

Since ICMP messages are rare, just use shared counters (atomic_long_t)

Per network space ICMP counters are still using percpu memory, we might
also convert them to shared counters in a future patch.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 14 deletions

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index 24b3558b8e67..18ff5df7ec02 100644
--- a/net/ipv6/proc.c
+++ b/net/ipv6/proc.c
@@ -141,7 +141,11 @@ static const struct snmp_mib snmp6_udplite6_list[] = {
 	SNMP_MIB_SENTINEL
 };
 
-static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, void __percpu **mib)
+/* can be called either with percpu mib (pcpumib != NULL),
+ * or shared one (smib != NULL)
+ */
+static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, void __percpu **pcpumib,
+				     atomic_long_t *smib)
 {
 	char name[32];
 	int i;
@@ -158,14 +162,14 @@ static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, void __percpu **mib)
 		snprintf(name, sizeof(name), "Icmp6%s%s",
 			i & 0x100 ? "Out" : "In", p);
 		seq_printf(seq, "%-32s\t%lu\n", name,
-			snmp_fold_field(mib, i));
+			pcpumib ? snmp_fold_field(pcpumib, i) : atomic_long_read(smib + i));
 	}
 
 	/* print by number (nonzero only) - ICMPMsgStat format */
 	for (i = 0; i < ICMP6MSG_MIB_MAX; i++) {
 		unsigned long val;
 
-		val = snmp_fold_field(mib, i);
+		val = pcpumib ? snmp_fold_field(pcpumib, i) : atomic_long_read(smib + i);
 		if (!val)
 			continue;
 		snprintf(name, sizeof(name), "Icmp6%sType%u",
@@ -174,14 +178,22 @@ static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, void __percpu **mib)
 	}
 }
 
-static void snmp6_seq_show_item(struct seq_file *seq, void __percpu **mib,
+/* can be called either with percpu mib (pcpumib != NULL),
+ * or shared one (smib != NULL)
+ */
+static void snmp6_seq_show_item(struct seq_file *seq, void __percpu **pcpumib,
+				atomic_long_t *smib,
 				const struct snmp_mib *itemlist)
 {
 	int i;
+	unsigned long val;
 
-	for (i = 0; itemlist[i].name; i++)
-		seq_printf(seq, "%-32s\t%lu\n", itemlist[i].name,
-			   snmp_fold_field(mib, itemlist[i].entry));
+	for (i = 0; itemlist[i].name; i++) {
+		val = pcpumib ?
+			snmp_fold_field(pcpumib, itemlist[i].entry) :
+			atomic_long_read(smib + itemlist[i].entry);
+		seq_printf(seq, "%-32s\t%lu\n", itemlist[i].name, val);
+	}
 }
 
 static void snmp6_seq_show_item64(struct seq_file *seq, void __percpu **mib,
@@ -201,13 +213,13 @@ static int snmp6_seq_show(struct seq_file *seq, void *v)
 	snmp6_seq_show_item64(seq, (void __percpu **)net->mib.ipv6_statistics,
 			    snmp6_ipstats_list, offsetof(struct ipstats_mib, syncp));
 	snmp6_seq_show_item(seq, (void __percpu **)net->mib.icmpv6_statistics,
-			    snmp6_icmp6_list);
+			    NULL, snmp6_icmp6_list);
 	snmp6_seq_show_icmpv6msg(seq,
-			    (void __percpu **)net->mib.icmpv6msg_statistics);
+			    (void __percpu **)net->mib.icmpv6msg_statistics, NULL);
 	snmp6_seq_show_item(seq, (void __percpu **)net->mib.udp_stats_in6,
-			    snmp6_udp6_list);
+			    NULL, snmp6_udp6_list);
 	snmp6_seq_show_item(seq, (void __percpu **)net->mib.udplite_stats_in6,
-			    snmp6_udplite6_list);
+			    NULL, snmp6_udplite6_list);
 	return 0;
 }
 
@@ -229,11 +241,11 @@ static int snmp6_dev_seq_show(struct seq_file *seq, void *v)
 	struct inet6_dev *idev = (struct inet6_dev *)seq->private;
 
 	seq_printf(seq, "%-32s\t%u\n", "ifIndex", idev->dev->ifindex);
-	snmp6_seq_show_item(seq, (void __percpu **)idev->stats.ipv6,
+	snmp6_seq_show_item(seq, (void __percpu **)idev->stats.ipv6, NULL,
 			    snmp6_ipstats_list);
-	snmp6_seq_show_item(seq, (void __percpu **)idev->stats.icmpv6,
+	snmp6_seq_show_item(seq, NULL, idev->stats.icmpv6dev->mibs,
 			    snmp6_icmp6_list);
-	snmp6_seq_show_icmpv6msg(seq, (void __percpu **)idev->stats.icmpv6msg);
+	snmp6_seq_show_icmpv6msg(seq, NULL, idev->stats.icmpv6msgdev->mibs);
 	return 0;
 }